WO2020263818A2

WO2020263818A2 - Source of photoluminescent light with reduced thermal quenching and use thereof

Info

Publication number: WO2020263818A2
Application number: PCT/US2020/039126
Authority: WO
Inventors: Loren HOBOY
Original assignee: Meadowstar Enterprises Ltd
Priority date: 2019-06-25
Filing date: 2020-06-23
Publication date: 2020-12-30
Also published as: WO2020263818A3

Abstract

Light-emitting photoluminescent (PL) cell configured to abate thermal quenching when exposed to high levels of radiant excitation; methods and systems of using the same for horticultural growth lighting and other lighting applications. Embodiment of a method for fabricating such cell includes vapor-depositing a first layer of optically-transmissive and thermally-transmissive (> 30 W/m-K; preferably > 10030 W/m-K; more preferably > 500 W/m-K) auxiliary material on an appropriately-shaped heatsink substrate. A PL material (preferably, a composite of chosen phosphor with the auxiliary material) is then applied on top of the first layer, followed by vapor-depositing a second layer of auxiliary material to encapsulate/seal the PL material between first and second layer

Description

SOURCE OF PHOTOLUMINESCENT LIGHT WITH REDUCED THERMAL QUENCHING

AND USE THEREOF

CROSS-RELERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from the US Provisional Patent Application No. 62/866,491 filed on June 25, 2019, the disclosure of which is incorporated by reference herein.

TECHNICAL FIELD

[0002] The present invention relates to generating photoluminescent light while reducing thermal quenching effects and, more particularly, to specific photoluminescent cells characterized by improved thermal conductivity and heat transfer and/or dissipation while generating incoherent photoluminescence (especially when such cells are exposed to high-power excitation radiation), as well as systems and methods utilizing such cells.

RELATED ART

[0003] Photoluminescence (PL) is light emission from any form of matter after the absorption of photons (electromagnetic radiation). It is one of many forms of luminescence (light emission) and is initiated by photoexcitation.

[0004] The process of generation of photoluminescent light - whether with the use of laser-light excited phosphor based lighting fixtures, or laser/LED hybrid laser sources, laser/phosphor hybrid light sources, or systems known as projector phosphor color wheels - is well known to be impeded by thermal quenching of photoluminescent materials used in such systems or sources. Thermal quenching is the term of related art that refers to the process of decrease in the luminescence efficiency of the phosphor at high(er) temperature due to the increase in the non-radiative transfer at those temperatures. While understanding the physical mechanisms behind thermal effects in phosphors is rather critical for various light-emitting device applications - in particular, while-light-emitting device applications - as thermal quenching of their photoluminescence might render such devices substantially useless, the process of thermal quenching itself is not of issue in this disclosure, and for that reason is not discussed in any length. Rather, the purpose of this disclosure is to find practical ways of reducing the effects of thermal quenching thereby creating a source of photoluminescent light (PL light) the efficiency of which is higher than that of a conventional PL source subject to thermal quenching.

[0005] Currently used phosphor-based PL sources of light have very low thermal conductivity: a combination of epoxy, acrylic, silicone, and other polymeric materials as well as glass, quartz, combined with photoluminescent material encapsulates (that is, active contents of the PL cell) and various binders are characterized by thermal conductivity that is generally below 10 W/m-K. Such low measure of the ability of the PL cells of related art to conduct heat results in rapid heat buildup in a given PL cell during the operation and resulting decrease of the light output. This thermal quenching of photon generation from the PL materials results when the phosphors and other encapsulates of a give PL cell of related art are subjected to high level of excitation radiation sources (for example, high-power lasers): high levels of waste heat and significant increase in the internal temperature of a given phosphor hinder the phosphor's ability to generate light. The thermal quenching problem is further exacerbated by the current choice of phosphors used in related art, which have rather low or poor thermal conductivity: even when an unadulterated

photoluminescent material is used, thermal quenching causes such material to unwanted oxidation.

[0006] Considering that the use of sources of incoherent light is wide - ranging from controlled- environment agriculture (CEA) used particularly for food production to illumination / lighting applications to image-projection applications - there remains a need in industry for a PL cell that, in operation, is characterized by abated or diminished thermal quenching (especially when the operation of such PL cell is driven by the use of high-power excitation radiation) and improved light-output irradiance/intensity as well as a PL-light-emitting device or system and method of utilizing such light output.

SUMMARY OF THE INVENTION

[0007] Embodiments of the invention provide an article of manufacture that includes a container

(that has a volume and an outer wall containing a first material that is substantially optically-transmissive at a wavelength in a spectral range from about 280 nm to about 13,000 nm and that has a thermal conductivity of at least 30 W/m-K), and a composite material contained in said volume and including a combination of a photoluminescent material and a second material. Here, the photoluminescent material is configured to generate photoluminescent light at the wavelength, and the second material is substantially optically- transmissive at the wavelength and has the above-specified thermal conductivity. The combination of materials in the volume of the container includes one of i) a mixture or blend of particles of the

photoluminescent material and particles of the second material; and ii) a layered structure including alternating first and second layers, the first layer containing the photoluminescent material and the second layer containing the second material. Such combination may be sintered. Alternatively or in addition, the article of manufacture may include heatsink in thermal contact with the container; and an excitation source structured to deliver excitation radiation to the composite material; and/or be structured to satisfy at least one of the following conditions: a) the container is dimensioned to include a flange radially protruding from an axis of the container and devoid of the composite material (here, the heatsink includes a heatsink element grasping or clamping the flange from first and second sides); b) the heatsink includes a channel therethrough dimensioned to transmit the excitation radiation to the container; c) the heatsink is in thermal contact with a heat-pipe; and d) the excitation source includes at least one of a laser, a light emitting diode (LED), and an optical fiber element. Alternatively or in addition - and substantially in any implementation of the article of manufacture - the composite material may be disposed is in direct physical contact and on the heatsink, and the heatsink may be in direct physical contact with the outer wall. Furthermore, in any of the above- identified cases, the article of manufacture may be structured to satisfy at least one of the following conditions: a) the volume is a volume of a hollow in the container (here, an aperture defined by the hollow is covered with a lid layer); b) the lid layer contains a lid material that is substantially optically-transmissive at the wavelength and that has the identify thermal conductivity; c) the lid layer includes the excitation source; d) the lid layer is fluidly sealing the aperture; and e) the first and second materials are the same material.

[0008] Embodiments of the invention additionally provide a color wheel light source structured to include a wheel substrate configured to rotate about an axis of the wheel substrate; a plurality of articles of manufacture (in any implementation identified above), each of which articles is disposed circumferentially on a surface of the wheel substrate in a peripheral region thereof in thermal contact with the wheel substrate; and a fan centered and rotating about said axis of the wheel substrate. Here, the wheel substrate is configured as an auxiliary heatsink in thermal contact with at least one of a heatsink and a container of each of the plurality of the articles of manufacture.

[0009] Embodiments of the invention provide a method for operating of an article of manufacture specified above. The method includes the steps of irradiating the composite material with excitation radiation to cause the composite material generate photoluminescent light at the wavelength; and at least partially transmitting said photoluminescent light through the outer wall. The step of irradiating may include include one of i) irradiating a mixture or blend of particles of the photoluminescent material and particles of the second material; and ii) at least partially transmitting the excitation radiation through a layered structure including alternating first and second layers, the first layer containing the photoluminescent material and the second layer containing the second material. Alternatively or in addition, the method maybe configured to satisfy at least one of the following conditions: a) to include transferring thermal energy between the combination and an ambient medium through a heatsink disposed in contact with the container; b) to include transferring thermal energy between the combination and the ambient medium through a heatsink element dimensioned to fittingly grasp a flange of the container from first and second sides of the flange, the flange protruding from an axis of the container and being devoid of the composite material; c) to include transferring thermal energy between the combination and the ambient medium through a heat-pipe; d) the step of irradiating includes delivering said excitation radiation through a channel in the heatsink; e) the step of irradiating includes delivering the excitation radiation from a source of the excitation radiation that is in contact with the combination; and f) the step of irradiating includes delivering the excitation radiation from at least one of a laser, a light emitting diode (LED), and an optical fiber element. In substantially any implementation of the method, at least one of the following conditions may be satisfied: a) the volume is a volume of a hollow in the container, where an aperture defined by the hollow is covered with a lid layer; b) the lid layer contains a lid material that is substantially optically-transmissive at the wavelength and that has the above-specified thermal conductivity; c) the lid layer includes the excitation source; d) the lid layer is fluidly sealing the aperture; and e) the first and second materials are the same material. In addition, substantially any embodiment of the method may include a step of rotating a wheel substrate about an axis of the wheel substrate (here, the wheel substrate contains or supports more than one of the articles of manufacture that are identified above and that are disposed circumferentially on a surface of the wheel substrate in a peripheral region thereof in thermal contact with the wheel substrate). Such wheel substrate is configured as an auxiliary heatsink in thermal contact with at least one of a heatsink and a container of each of the plurality of the articles of manufacture. At the same time, this implementation of the method additionally includes transferring thermal energy between the wheel substrate and the ambient medium by operating a fan centered and rotating about the axis of the wheel substrate. Alternatively or in addition, substantially any implementation of the method may include a step of irradiating at least one of a plant, a backside of a display screen, and a surface of a building with said photoluminescent light that has been at least partially transmitted through the outer wall; or steps of - irradiating a target with the photoluminescent light that has been at least partially transmitted through the outer wall, and - generating the excitation radiation by operating a laser excitation source in one of a continuous wave (CW) fashion and a pulsed fashion. (Here, when the target is a plant, such pulsed fashion may be characterized by at least one of: - pulse frequency between 20 kHz and 70 kHz; - pulse duration between 10⁵ and 10 ³ second; and - a duty cycle of about 30% (in order to allow waste heat delivered to the plant to dissipate when a laser pulse is off).

[0010] Embodiments of the invention also provide a use of a light source for illumination of a target surface (such light source comprising a photoluminescent (PL) cell, a laser excitation source optically coupled to the PL cell, and a power source of the laser excitation source). The use includes delivering excitation radiation from the laser excitation source, disposed with the power source outside of the CEA environment, to the PL cell through a fiber-optic element; and irradiating a composite material enclosed in the PL cell with the excitation radiation to generate PL light at a wavelength in a spectral range from about 280 nm to about 13,000 nm. (Here, the composite material includes a combination of a photoluminescent material and a filler material, the photoluminescent material is configured to generate the PL light, and the filler material is substantially optically-transmissive at the wavelength and has thermal conductivity of at least 30 W/m-K). The use further includes at least partially transmitting said PL light through a wall of the PL cell (here, such wall includes a wall material that is substantially optically-transmissive at said wavelength and has thermal conductivity of at least 30 W/m-K), and irradiating the target surface with output PL light that has been at least partially transmitted through said wall (here, the target surface may include a wall or floor or ceiling or a back side of a display screen, in some specific cases). The use may additionally include transmitting light, emanating from the display screen as a result of the irradiating the target surface, through an optical diffuser.

[0011] Embodiments additionally provide the use of a light source for reducing heat stress of a plant in controlled environment agriculture (CEA) environment. (Such light source contains a photoluminescent (PL) cell, a laser excitation source optically coupled to the PL cell, and a power source of the laser excitation source). The use includes delivering excitation radiation from the laser excitation source, disposed with the power source outside of the CEA environment, to the PL cell through a fiber-optic element; and irradiating a composite material enclosed in the PL cell with the excitation radiation to generate PL light at a wavelength in a spectral range from about 280 nm to about 13,000 nm. (Here, the composite material includes a combination of a photoluminescent material and a filler material, the photoluminescent material is configured to generate the PL light, and the filler material is substantially optically-transmissive at said wavelength and has thermal conductivity of at least 30 W/m-K). The use additionally includes the step of at least partially transmitting the PL light through a wall of the PL cell (where the wall includes a wall material that is substantially optically-transmissive at the wavelength and has thermal conductivity of at least 30 W/m-K), and irradiating the plant with output PL light that has been at least partially transmitted through the wall. Alternatively or in addition, the step of irradiating may include generating the PL light while at the same time reducing thermal quenching of the photoluminescent material in the composite material; and/or locating the PL cell located outside the CEA environment while the step of irradiating the plant includes delivering the output PL light to the plant with the use of an auxiliary fiber optic element. The laser excitation source may be operated - depending on the specific implementation - in a pulsed fashion characterized by at least one of: - pulse frequency between 20 kHz and 70 kHz; - pulse duration between 10⁵ and 10 ³ second; and - duty cycle of about 30% (in order to allow waste heat delivered to the plant to dissipate when a laser pulse is off). Substantially in any implementation of the use of the light source, the light source may be configured to satisfy at least one of the following conditions: a) the wall material and the filler material include at least one of synthetic diamond, CVD diamond, polycrystalline diamond, monocrystalline diamond, sapphire, cubic boron arsenide, gallium arsenide, gallium phosphide, and gallium nitride; b) the wall material and the filler material are the same material; c) at least one of the wall material and the filler material has a thermal conductivity value within a range from about 500 W/m-K to about 2,000 W/m-K; d) the photoluminescent material includes at least one of a phosphor-based light emitting material, a nanotube, a light-emitting nanocrystal, a fluorescent nano-diamonds, a doped waveguides and/or light pipes, a doped diamond, a doped crystal, a quantum dot, and a scintillator; e) the filler material includes first material particles with an average size between 2 microns and 30 microns; and f) the filler material includes second nano-sized material particles. Alternatively or in addition - and in substantially any implementation of the use - at least one of the following conditions may be satisfied: a) the use comprises at least one of - transferring thermal energy between the composite material and an ambient medium surrounding the PL cell through a heatsink disposed in contact with the PL cell; - transferring said thermal energy between the composite material and the ambient medium through a heatsink element disposed to fittingly grasp a flange of the PL cell from first and second sides of the flange, the flange protruding from an axis of the container and being devoid of the composite material; and - transferring thermal energy between the composite material and the ambient medium through a heat-pipe; b) the step of irradiating includes delivering the excitation radiation through a channel in the heatsink; c) the step of irradiating includes delivering the excitation radiation from the laser excitation source through an optical element that is in contact with the PL cell; and d) the step of irradiating includes delivering the excitation radiation from at least one of the laser excitation source, a light emitting diode (LED), and an optical fiber element.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention will be more fully understood by referring to the following Detailed Description of Specific Embodiments in conjunction with the not-to scale Drawings, of which:

[0013] Fig. 1 is a schematic illustration of an embodiment of a PL cell of the invention, combined with a heatsink.

[0014] Fig. 2 shows modifications to the embodiment of Fig. 1.

[0015] Fig. 3 depicts a related embodiment of the PL cell of the invention, cooperated with a heatsink.

[0016] Fig. 4 illustrates a structure and/or method for fabrication of an embodiment of the PL cell according to the idea of the invention.

[0017] Fig. 5 shows the embodiment of PL cell of Fig. 5 modified with a clamp-like heatsink element.

[0018] Fig. 6 represents the embodiment of Fig. 5 operably attached to a bulk heatsink.

[0019] Figs. 7A, 7B illustrated additional related embodiments of a PL cell according to the idea of the invention.

[0020] Fig. 8 shows yet another embodiment of a PL cell structured in a layered fashion.

[0021] Fig. 9 presents a modification to the embodiment of Fig. 8. [0022] Fig. 10 illustrates the cooperation between the embodiment of Figs. 8, 9 and the clap-like heatsink element.

[0023] Fig. 11 is a schematic showing an arrangement structured for delivery of PL light, generated by an embodiment of the invention, towards intended target.

[0024] Fig. 12 schematically illustrates a lighting system employing a PL cell structured according to the idea of the invention.

[0025] Figs. 13A, 13B provide views of a "color wheel" system employing at least one embodiment of a PL cell and structured as a spatially- and/or spectrally-reconfigurable source of PL light.

[0026] Fig. 14 shows a particular spatial cooperation of a specific implementation of the "color wheel" system of Figs. 13A, 13B with a source of excitation radiation and intended target.

[0027] Figs. 15, 16, and 17 illustrate the use of embodiment(s) of the invention for the purposes of controlled-environment agriculture.

[0028] Fig. 18 is a plot illustrating optical spectrum of light absorbed by plants for photosynthesis.

[0029] Fig. 19 is a plot illustrating details of wavelength spectra of light absorbed by plants for photosynthesis.

[0030] Fig. 20 shows schematically an optical system for use in display-related (back-side projection) applications and utilizing embodiment(s) of PL light configured according to the idea of the invention.

[0031] Fig. 21 illustrates a lighting system configured for illumination of a building or another structure and containing remotely-disposed lighting fixtures that employ embodiment(s) of the invention as well as optics, configured to room and/or area lighting applications.

[0032] Fig. 22 illustrates the alternative embodiment of the invention.

[0033] Generally, the sizes and relative scales of elements in Drawings may be set to be different from actual ones to appropriately facilitate simplicity, clarity, and understanding of the Drawings. For the same reason, not all elements present in one Drawing may necessarily be shown in another. Like elements and components are generally indicated / denoted with like numerals and labels.

DETAILED DESCRIPTION

[0034] The use of benefits of phosphor-converted light-emitters is well known. A significant challenge in this field is the phenomenon known as thermal quenching, which takes place inside phosphor used for light emissions and leads to a significant reduction in the emission intensity under high-power excitation operation. One approach has been to address the problem with the development of more thermally stable phosphors but does not address the real underlying problem, poor heat transfer removal at the phosphor-particle interface. It is known, for example, that if a YAG:Ce phosphor operating at 300K (26.85C) is deemed to emit at 100% capacity, then that emission level will generally decrease to about 60% at 473 K (200 deg C) and about 40% at 600 K (327 deg C).

[0035] In accordance with embodiments of the present invention, apparatus and methods are disclosed configured to generate and utilize incoherent photoluminescent light in a specifically-configured fashion - while abating thermal quenching of the PL material emitting such light and while reducing the amount of waste heat delivered to the target of illumination.

[0036] The persisting problem of thermal quenching of PL material contents of PL cell(s) used in conventional devices and systems is solved by modifying such contents. The idea of the invention stems from the realization that temperature-dependent properties of conventional phosphor(s) used in PL cells are substantially improved when such phosphor(s) not only are mixed or combined with highly-thermally- conducting material to form a composite material configured to remove the heat from the phosphor(s) during the excitation of such phosphor(s) with the purpose of generation of photoluminescence, but are also encapsulated (housed) in a PL cell made of the same highly-thermally-conducting material. In other words, implementations of this invention significantly improve the removal of waste heat generated from within the phosphor and diamond composite as well as at the composite boundaries to maintain a lower internal phosphor temperature and minimize thermal quenching due to high temperatures as the excitation energy is increased by reducing the thermal resistance of the system.

[0037] Moreover, the judicious choice of such highly-thermally-conducting material to be a material of operationally-sufficient optical transmittance at the wavelengths of interest addresses the second problem of related art - that is, the problem of inability to maximize the delivery of the already-generated PL light through the body / wall of the PL cell.

[0038] According to the idea of the invention, such highly-thermally-conductive and optically- transmissive materials and PL materials in a composite may be comprised of particles, crystals, and/or solids. The composite of at least one PL material and highly-thermally-conductive material may be formed from particles, compressed cake, compressed pellet, sintered material or calcined material and/or the composite material layer may be capped or layered between one or more thermally conductive material layers that form an envelope or shell around the composite material layer.

Examples of Embodiments

[0039] Fig. 1 illustrates, in a cross-sectional view, an embodiment 100 that includes an article of manufacture (a photoluminescent cell) 110, structured as a container or cell that has a shell enclosure dimensioned to define an inner volume of such container, and a heatsink 120 in physical and thermal contact with the article 110. The inner volume of the container is at least partially filled with the composite material 124 that includes a combination (a mixture, a blend, or a differently-configured combination) of materials at least one of which is a photoluminescent material component 124A and at least one more of which is a filler material component 124B of choice.

[0040] Generally, the choice of the PL material component 124 A of the composite material 124 is defined by its ability to emit photoluminescent light at a wavelength within the spectral range from about 280 nm to about 13,000 nm, when irradiated with the appropriate excitation radiation at a wavelength within substantially the same spectral range that excited the upconversion or down conversion process(es) in the chosen PL material. In reference to this and other embodiments described in this disclosure, examples of the photoluminescent material of choice include but are not limited to a phosphor-based light emitting material, a nanotube, a light-emitting nanocrystal, a fluorescent nano-diamonds, a doped waveguides and/or light pipes, a doped diamond, a doped crystal, a quantum dot, a scintillator, and a combination of one or more of these.

[0041] The choice of the filler material component 124B of the composite material 124 is driven by a need to have the filler material, on the one hand, be substantially optically-transparent at a wavelength of the PL emitted by the PL material and, on the other hand, to possess high thermal conductivity - generally, at least 30 W/m-K (as a reference temperature of 300 K) and preferably higher - up to 500 to 2,000 W/m-K. Examples of the filler material include but are not limited to synthetic diamond, CVD diamond,

polycrystalline diamond, monocrystalline diamond, sapphire, cubic boron arsenide, gallium arsenide, gallium phosphide, and gallium nitride. Additional discussion of the PL materials and/or filler materials appropriate for use with an embodiment of the invention is presented elsewhere in this disclosure.

[0042] As shown, in the embodiment 100 the container 110 has an outer wall or layer 128 that is at least in part (and, preferably, completely) made of a container material that is substantially optically- transparent at least one of the wavelength of PL (that the composite material emits when appropriately irradiated with the excitation radiation) and the wavelength of the excitation radiation itself. The shown version 110 of the container or cell includes a lid layer or element 132 substantially fluidly sealing an aperture providing ingress and egress into the volume of the container.

[0043] For completeness of the illustration, Fig. 1 schematically shows the flux of excitation radiation F (coherent or at least partially incoherent - depending on the specific details of the particular implementation). The excitation radiation F is chosen, in operation of the embodiment 100, to be delivered to and irradiate the composite material 124 through the shell of the container 110 (as shown - through the outer wall or layer 128) to cause the PF material component 124A of the composite material 124 emit output photoluminescence O. The output photoluminescent light O is shown to be is at least partially transmitted through the wall 128 (where it can be appropriately collected or otherwise handled, as discussed below). While shown in the cross-sectional view of Fig. 1 to be substantially rectangular, the shape of the wall 128 generally does not affect the principle of configuration of the specific implementation of the container or cell 110, and can be dimensioned to be perceived - when viewed along the axis 136 of the cell - as a parallelepiped or cuboid, a conical structure, or a cylindrical structure, to name just a few. Notably, in at least one specific case a portion 128A of the wall 128 that is used to collect / acquire the useful PL output O may be shaped to possess a non-zero optical power (thereby configuring the portion 128A to become an optical lens element) to facilitate the collection and/or spatial shaping of the photoluminescent output O, depending on the circumstances of the particular application of the embodiment.

[0044] The excitation radiation L may be laser light in the UV-blue portion of the visible spectrum

(from about 350 nm to about 500 nm) and/or an infrared (IR) laser light at a wavelength within a range from about 840 nm to about 1,100 nm. In one specific example, the composite material 124 contains particles or “dust” of a diamond-based substance (with transmission at a PL wavelength of interest of preferably greater than 50%) as a filler material 124B. The sizes of these particles range from about several microns (for example, 1 micron or 2 microns) to about 100 microns (and in one case - with an average size from about 20 microns to about 30 microns), thoroughly intermixed with the particles of a PL phosphor-based material 124A (for example a YAG:Ce3+ phosphor sized between about 2 and about 20 microns, with the average size of about 6 microns for optimal performance) to form the initial mixture and then tightly compressed into the volume of the container 110 to establish operationally-reliable thermal contact between the PL material 124A and the filler material 124B. Smaller particles of the filler material (for example nano-sized particle, as small as 5 nm in one non-limiting example) may be additionally incorporated to the mixture to fill voids, if any. At least one of the lid layer 132 and the outer wall 128 may be also made of the same filer material (with transmission of preferably 50% at the PL wavelength of interest) - this time, however, structured as a bulk or a layer. In one specific example, the thickness of the wall or layer 128 and/or lid layer 132 may be about 0.2 mm (generally - between about 0.1 mm and about 0.5 mm), while the overall cross-sectional size of the cell 110 may be about 3 mm². The composite material 124, compressed against the shell of the container 110, forms a reliable thermal contact with the shell (the lid 132 and/or the outer wall 128) to transfer thermal energy, generated in the composite material 124 irradiated with energy L, through the shell of the container between the material 124 and the heatsink 120.

[0045] Fig. 2 provides a schematic illustration of a structure of a related embodiment 200, in which the heatsink 120 includes a hollow or a channel 230 therethrough that is appropriately dimensioned to allow for delivery of the excitation radiation - in operation of the embodiment 200 - to the cell or container 110. In this case, the excitation radiation L reaches the composite material 124 after being at least partially transmitted through the lid layer 132. [0046] Understandably, a constituent photoluminescent cell or container - such as the cell 110 of

Figs. 1, 2 - can be constructed on its own, thus representing the basic embodiment of the invention, and later on operably juxtaposed or cooperated with the heatsink element and/or system.

[0047] Fig. 3 illustrates schematically yet another related embodiment 300 in which - in comparison with the embodiment 100 - the lid layer at least partially covering the aperture of the shell of the cell 110 is formed at least in part by a light-emitting diode 314 that, in operation, provides a radiative contribution (not marked) to the excitation radiation delivered to the composited material 124 for generation of photoluminescence. Both a portion of the shell (envelope) of the container 110 and the LED 314 are shown to be in thermal contact with the heatsink 120. The portion of the excitation radiation delivered to the material 124 through the outer wall 128 from the front is shown as L (by analogy with that of Fig. 1). The aggregate excitation radiation includes radiation L (preferably, laser light in the UV-blue portion of the optical spectrum - for example, between 350 nm and 480 nm) combined with the light output form the LED 314 that is thermally connected to the heatsink 120 and encapsulated in the high heat transfer and light transmissive material envelope of the shell of the PL cell 110.

[0048] Fig. 4 presents a simplified cross-sectional view of yet another related embodiment, in which the PL cell 402 containing the composite material 124 is formed with the substantially fluidly sealed shell 404 having a wall/layer 428 and a lid layer or element 432. In this example, however, a surface 420A of the substrate 420 (which, in one case, can be configured as a heatsink element) has a pocket or notch or depression 424 judiciously dimensioned such that, when the material forming the shell 404 (such as a diamond-based material with the thermal conductivity of at least 30 W/m-K, as a reference temperature of 300 K, and preferably higher - up to 500 to 2,000 W/m-K) is vapor-deposited in the appropriately- configured vacuum process (for example, a CVD deposition process) onto the surface 420, the wall 438 is formed. In this specific example, the cross-section of the wall 420 in a plane containing the axis (not shown) of the PL cell 402 is trapezoidal, but generally can be chosen to have substantially any shape (rectangular or triangular being but examples). The lid 432 is used to cover the chamber / volume of the shell after the composite material 124 is compressed in that volume. In one specific example of manufacture of this implementation, the material of choice for fabrication of the cell / container 402 is optical CVD

polycrystalline diamond and that for the filler material component 124B of the composite material 124 is diamond particles or crystals with thermal conductivity greater than 700 W/m-K and optical transmittance greater than 70% at the wavelengths of interest (and, in the case when an outer surface of the lid layer 432 is coated with the AR-coating - preferably of at least 98%). The filler material is judiciously chosen such that the thermal conductivity of the overall composite material 124 is greater than 35 W/m-K. In a related implementation, aluminum nitride (17-285W/m K) may be chosen instead of the polycrystalline diamond with visible light transmission of about 75-85%.

[0049] In one specific example of implementation - and in further reference to Fig. 4 and related embodiments - the composite material 124 is constructed by mixing a 0.11 g/cm3 YAG:Ce³⁺Phosphor (material component 124A) with a 2 microns to 30 microns particle size and a 99.9 weight-% content of optical diamond crystal particles (material component 124B) sized from about 7 microns to about 20 A copper Round Pin Heatsink sink 420 is selected with a plate thickness of at least 3 mm, into which a 2.6 mm diameter by 0.7 mm depth hole is drilled and machined to provide 0.25 mm radius rounding to every "comer" (this way, the internal space does not have rectilinear comers - but rounded ones). A first layer of CVD diamond material 428, 3mm in diameter centered on the hole, is applied at 0.5mm thickness on the copper heatsink. The well-blended composite 124 is placed in the 0.2 mm remaining hole on top of the CVD- diamond-coated copper heatsink (that is, on top of the layer 428). The diamond dust and phosphor composite 124 is then compressed at a pressure of about 4 GPa (generally - from about 3.9 GPato about 4.2 GPa) into the hole utilizing a hydraulic press. A second layer of 0.5 mm thick CVD diamond material layer 432 is then deposited as known in the art (for example, as provided by Element Six Technologies Inc or other CVD service providers).

[0050] When the substrate 420, used for deposition of the layer 428, is not configured as a heatsink, the PL cell 402, once formed, is removed / separated from the substrate 420 and, when desired, is physically juxtaposed in good thermal contact with the appropriately shaped heatsink (whether along the surface of the layer 432, or along the surface of the layer 428). Fig. 5 schematically illustrates this situation, by showing 500 the embodiment 402 of the PL cell (encapsulating / enveloping the composite material 124 with the overall thermal conductivity of at least 30 W/m-K and bound by the sheets of layers 428, 432 of the optically transmissive material(s) having the thermal conductivity of at least 30 W/m-K), that has been removed from the mold substrate 420. Here, the flange 508 of the cell 402 (formed by the portions of the layers 428, 432 extending radially from the axis 536 of the cell 402 and not containing any portion of the composite material 124) is complemented with a clamp-like thermally-conducting element 540, grasping the flange on first and second sides. The element 540 is configured to be a heat-sink element. While the heatsink element 540 is shown in Fig. 5 to be juxtaposed with the cell 402 in two locations, more generally such element 540 can be attached to the flange of the PL cell at any location of the perimeter of the flange 508 - for example, around the whole perimeter such as to circumscribe the flange 508. Line 536 represents the axis of the cell 402, which is perpendicular to at least one of the layers 428, 432.

[0051] Fig. 6 schematically illustrates, 600, the embodiment of Fig. 5 loaded into (connected to) the heatsink 620, which may be configured to have an optional hollow or channel 630 therethrough, such that at the heatsink element 540 and/of a portion of the body of the cell 402 is brazed into the heatsink 620 when metallized and bonded with a heat-conductive material (solder of sorts) to establish thermal contact with such heatsink. The arrows L, O illustrate the delivery of excitation radiation (preferably, a laser light at 350 nm to 480 nm or at 840 nm to 1, 100 nm, or generally at a wavelength from about 250 nm to about 13,000 nm) and the generated PL light, respectively, during the use of the combination(s) 500,600. While not shown explicitly in Fig. 6, the person of ordinary skill in the art will appreciate that the PL light O generated by the embodiment 600 is delivered to the ambient both forward and backward (that is, through both the wall of the container and the lid element) along the axis 536. Each of the surfaces of the PL cell 402 can be appropriately coated with athin-film antireflection stack of materials.

[0052] Referring now to Fig. 7A - and in further reference to Fig. 5 - when the mold 420 is configured as a heatsink to begin with, the embodiment of the heatsink-connected PL cell 402 can be complemented with at least one of the two additional material layers: the appropriately designed thin-film high-reflectance layer 710 (the deposition of which onto the surface 420A of the substrate 420 precedes the deposition of the layer 428) and the anti-reflection coating 712 deposited on and carried by the lid layer 432. A skilled artisan will readily appreciates that with the use of the layer(s) 710 and/or 712 the outcoupling of the PL light O through the layer 432 to the ambient medium can be increased. Fig. 7B depicts an optional configuration in which the embodiment incorporating the PL cell is further complemented with a cooling vapor chamber or heat-pipe 730 in thermal connection with the heatsink 420. (A skilled artisan readily recognizes that a heat-pipe is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to effectively transfer heat between two solid interfaces. At the hot interface of a heat pipe a liquid in contact with a thermally conductive solid surface turns into a vapor by absorbing heat from that surface. The vapor then travels along the heat pipe to the cold interface and condenses back into a liquid - releasing the latent heat.)

Additional Examples of Embodiments.

[0053] Figs. 8, 9 illustrate related embodiments 800 of the PL cell (in both cases shown in thermal contact with the heatsink 810, 910 (the first one being devoid of a hollow therethrough, the second one having such a hollow 930). The PL cell 800 has an axis 836, and includes a container 820 formed from the container material (as discussed elsewhere in this disclosure) and having an optically-transmissive wall 828. The volume 830 within the container (shown in this example as three volume portions) contains with the composite material 124 or the PL material component 124A which, when irradiate as discussed elsewhere with the radiation L generates the photoluminescence O (which is further transmitted through the wall 828 and acquired / collected / processed as needed by a particular application). Overall, the cell 800 contains and can be viewed as a layered structure composed of alternating with one another first and second layers: the first layer being a layer of the container material and the second layer being a layer of the composite material 124 (or, in a specific case, the PL material component 124A). Fig. 10 shows the embodiment 800 thermally cooperated with the heatsink element / clamp 540 to remove the heat generated by the material contents of the volume 830; the result of such cooperation is a PL cell unit 1000.

[0054] A skilled artisan will recognize that the fabrication of an embodiment of the PL cell can be carried out as follows: a first optical transmissive and thermally transmissive window or envelope material layer is deposited on a temporary substrate via CVD deposition, followed by deposition of a PL material (such as composite material 124, for example, which may be sintered) onto the CVD window/envelope layer, then a second optical transmissive and thermally transmissive window or envelope material is deposited by CVD over the PL material to sandwich and encapsulate such PL material layer. The sequence of these steps may be repeated to create a multilayer structure. The so-formed PL cell (that is, at least one layer of the PL material encapsulated with and/or within the highly thermally-conductive and optically-transmissive material of the shell of container of the PL cell) can be then removed from the temporary substrate and then thermally connected to a heatsink. In one embodiment, metal bonding utilizing thermal compression bonding, diffusion bonding, pressure joining, thermos-compression or solid-state welding techniques may be employed. It is understood that, when the PL cell is formed on the substrate that is configured as a heatsink to begin with, the separation of the formed PL cell from the heatsink-substrate may not be required. The methodology of fabrication may be modified: first, a PL material (a composite 124, which may be sintered) may be applied or deposited directly onto an appropriately-configured substrate that includes a heatsink, then a CVD layer of an optical transmissive and thermally transmissive window or envelope material is deposited over the PL material to encapsulate and thermally connect this PL material to the heatsink substrate.

[0055] It is appreciated, therefore, that embodiments of the invention provide an article of manufacture (which, in its simplest form is a judiciously constructed photoluminescent cell - and, in a more developed form, is a system containing such a cell) that includes a container having a volume and an outer wall or volume-forming layer that contains a first material (such first material is substantially optically- transmissive at a wavelength in a spectral range from about 280 nm to about 13,000 nm and has a thermal conductivity of at least 30 W/m-K). The volume of the container is at least partially-filled with a composite material that includes a combination of a photoluminescent material and a second material. (The photoluminescent material is configured to generate photoluminescent light at the wavelength, while the second material is substantially optically-transmissive at the wavelength and has the above-identified thermal conductivity.) The composite material can be sintered. [0056] The article of manufacture may additionally include at least one of a heatsink in thermal contact with said container; and an excitation source configured to deliver excitation radiation to the composite material (in which case such article of manufacture is configured as a source of light) and, alternatively or in addition, be configured to satisfy at least one of the following conditions: a) the container is dimensioned to include a flange radially protruding from an axis of the container and devoid of the composite material, while the heatsink includes a heatsink element grasping or clamping the flange from first and second sides; b) the heatsink includes a channel therethrough dimensioned to transmit the excitation radiation to the container; c) the heatsink is in thermal contact with a heat-pipe; and d) the excitation source includes at least one of a laser, a light emitting diode (LED), and an optical fiber element.

[0057] Collection or acquisition of the photoluminescence produced in operation by an embodiment of the invention can be carried out in any of the conventional ways, for example with lens(es) and/or - when the collected PL light has to be delivered to the distant target region - with the use of a fiber-optic element. This situation is schematically illustrated in Fig. 11, in which the PL cell is shown to be of the variety 402 and energized by the excitation radiation L that is channeled through the associated heatsink component, while the produced photoluminescent output O is channeled with the optical relay system containing lenses 1110,1114 and the fiber optic 1120 towards the target. A skilled person will readily appreciate that in substantial any embodiment the delivery of the excitation radiation L to the composite material 124 contained in the PL cell of the embodiment can also employ a fiber-optic element. For example, Fig. 12 schematically depicts an embodiment employing multiple sources 1210 of excitation radiation (preferably, laser sources, driven by the power drivers 1210A) that are optically cooperated with and exciting a single PL cell through fiber-optic components 1220 that pass through the hollow (not shown) of the heatsink. In one specific case, the output ends / facets of the components 1220 may be directly fused to the wall / housing of the PL cell.

Examples of Embodiments Configured as“Color Wheels”

[0058] Individual implementations of PL cells can be combined in various fashions to form systems of incoherent lights sources. Figs. 13A, 13B, 14 provide schematic illustration to one of such systems, configured as a "color wheels" incorporating a plurality of individual PL cells (each configured according to one of embodiments of the invention).

[0059] Figs. 13A and 13B illustrate a "color wheel" light source in front and side views, respectively. As shown, a substantially disk-shaped substrate 1310 having an axis of rotation 1310A and made of a thermally-conductive (heatsink-like) material - for example, material including copper and/or aluminum - provides support for a multitude of PL cells (shown in this case as embodiments 500, 1000; each of which is removably affixed in sufficient thermal contact with the substrate 1310). During the operation, the wheel shaft may be driven by a motor (not shown). Juxtaposed with the wheel substrate 1310 is the axial fan 1320 that is thermally connected to the wheel 1310 and, in operation, draws air across the fan blades 1320A thereby transferring the thermal energy from the wheel substrate 1310 to the ambient medium and cooling the substrate 1310.

[0060] As shown in this case, synchronized with the rotation of the wheel, the PL composite materials 124 of different PL cells may be excited with CW or pulsed laser light beams L at different wavelengths (chosen to respectively correspond to the phosphor-based material component 124A of the respective composite material to generate PL light O at the PL-wavelength of interest), such that in general the operating wheel system 1300 is configured as a spatially- and/or spectrally-restmcturable source of incoherent light delivered along the axis 1310A. The colors of generated light are thus displayed sequentially at a rate dependent on the rate of rotation of the wheel.

[0061] Fig. 14 schematically depicts a related embodiment 1400, in which at least one of the PL cells 1410 is configured to be excited with radiation L delivered from the side that is opposite to the side from which the generated PL light O is emitted (for example, embodiments 200, 600, 900 can be used for this purpose), while the incoherent light O is further collected and remotely-transferred with the optical arrangement discussed in reference to Fig. 11. The remaining structures and/or operational features of the embodiment 1400 are sufficiently the same as those of the embodiment 1300.

Evidence of Thermal Abatement and Efficacy of Embodiments Over Current Technology.

[0062] To assess performance of an embodiment of the present invention in light that of a conventional PL cell, a simple thermal transfer analysis can be conducted comparing the waste heat dissipation of a copper heat sink with a phosphor/silicone composite and a

phosphor/A1203 sintered composite with the performance of the CVD encapsulation of the

Phosphor/Diamond dust material composition of this invention. A maximum temperature of 200 C (473 K), assuming an ambient Temperature of 25 C, is selected. As can be appreciated from the data of Table 1, the maximum heat transfer is 26 to 114 times (1720/65=26, 1720/15=114) greater in the case of using the embodiment of the invention when using the phosphor/diamond composite as discussed above.

[0063] Table 1

Additional Considerations for Configuring Embodiments of the Invention.

[0064] Generally, substantially every embodiment of a PL cell includes an envelope / shell configured as a heat-spreading container or housing designed to carry high waste heat loads away from the excited phosphor particles of the composite material within such housing when excited by laser light having power in the range from about 3 W to about 10,000 W or more and delivered within a very narrow excitation area at the composite material to approximate a substantially point source of PL light. Suchenvelope is approximately 3 mm² in a cross-section when the PL cell is about 1 mm in diameter, and generally between 0.1 mm and 0.5 mm in thickness,, but can be modified based in the heat transfer design requirements of the underlying heat sink so as to ideally maintain the PL cell below 100 °C (375 K) and reduce thermal quenching emission level losses to less than 10% as compared to emissions (at a room temperature of about 26 C).

[0065] The surface contact area for a thermal connection between the PL cell (such as cell 800, for example) and the waste heatsink (such as heatsink 810, for example) generally will be at least 1.5 times the diameter of the PL cell when using a copper heatsink, to be sufficient to conduct away the waste heat generated within the cell to maintain the PL material component 124A within the cell at a temperature below the desired temperature of a selected phosphor for thermal quenching avoidance and preferably below 100 °C at a maximum ambient air temperature of 55 °C (when taking into account the waste heat generated upon contact by the excitation source beam within the photoluminescence materials encapsulated in the photoluminescent cell).

[0066] Generally, the encapsulated composite material 124 may include up from about 1 weight-% to about 99.9 weight-% diamond particles to maximize thermal conductivity and maximize light transmission. The compacted diamond particles generally have a density of about 1.0 g/cm³ 1.5 gm/cm³. The diamond-based shell of the PL cell (the outside envelope or container of the PL cell, enclosing and encapsulating the composite PL material) provides thermal conductivity when thermally connected to a heatsink or heat dissipation mechanism, which protects against thermal quenching, chemical oxidation and humidity degradation while significantly improving waste heat removal. The photoluminescent materials composited and thermally connected to high heat transfer particles connect thermally to the high heat transfer envelope material.

[0067] Prior to diamond encapsulation of the active (~ photoluminescent) material or during such encapsulation process, the photoluminescent material or photoluminescent-diamond composite may be optionally subjected to calcification to remove moisture and waters of hydration or sintered under conditions known to those skilled in the art for photoluminescent materials (generally, at a temperature between 1100 C and 1700 C).

[0068] The heat transfer within the composite PL material configured as a compressed cake may be greater than 200 W/m-K and may reach 700-1,000 W/m-K. When compressing the composite mix of materials 124A, 124B, compression pressure should remain below the point where diamond crystals are fractured to minimize the negative effect on thermal conductivity inside the pellet. Preferred

photoluminescent materials and poly crystalline diamond composite utilizing 30 pm diamond particles with a diamond content ranging between 95% and 70% by volume using 4.1-4.2 GPa compression. For purposes of estimating weight or volume ratios specified herein, a person of ordinary skill in the art is invited to assume bulk density of compacted particles to be approximately 50% of the density of the subject elements or compound. Another alternative compression pressures may comprise pressures at 10 MPa and then anneal the photoluminescent materials at approximately 200 °C to 350 °C.

[0069] Selection of Phosphor (s).

[0070] It was empirically determined a phosphor particle size ranging from about 2 microns o about

20 microns (with a 6 micron average) may be preferred optimal performance of the PL material component of the composite material used in embodiments of the invention. The photoluminescent material can be of any known type, preferably selected from those offering the highest photoluminescence quantum efficiency and from groups having the highest Debye temperature to minimize the risk of thermal quenching. [0071] Photoluminescent material composites 124 may be selected, depending on the specific implementation, from at least one of strontium borate phosphor SrB6O10:Pb, Barium silicate phosphor BaSi205:Pb, strontium fluoborate phosphor SrFB203.5: Eu2+, strontium borate phosphor SrB407:Eu, calcium tungstate phosphor CaW04:[W], calcium tungstate phosphor CaW04:Pb, strontium pyrophosphate phosphor Sr2P207:Eu, strontium phosphate-chloride phosphor Sr5Cl(P04)3: Eu2+, calcium barium strontium phosphate chloride phosphor (Ca Sr Ba)3(P04)2C12:Eu, barium aluminates: europium phosphor BaA18013:Eu2+, strontium aluminates: europium phosphor Sr4A114025:Eu, strontium fluorophosphates phosphor Sr5F(P04)3:Sb,Mn, zinc silicate phosphor Zn2Si04, magnesium barium aluminates:

BaMg2A116027:Mn2+, gadolinium oxy sulfide phosphor Gd202S:Tb, yttrium phosphate vanadate phosphor Y(PV)04: Eu, strontium zinc phosphate phosphor (ZnSr)3(P04)2: Mn, yttrium oxysulfide phosphor Y202S:Eu, magnesium manganese borate phosphor (CeGd)(MgMn)B5O10, strontium magnesium phosphate phosphor (Sr Mg)3(P04)2:Sn²+, magnesium fluogermanate phosphor

3.5MgO 0.5MgF2 Ge02:Mn, magnesium arsenate phosphor Mg5As2011 : Mn, calcium silicate phosphor CaSi03:Pb,Mn, calcium fluorophosphates phosphor Ca3(P04)2 CaF2:Ce,Mn.

[0072] Composite materials utilizing such QDs may include at least one of CsPb(Cl/Br)3 QDs ( with peak emission at about 450 nm), CsPb(Cl/Br)3 QDs (~ 480 mn peak emission); CsPbBr3 QDs (- 510 mn peak emission), CsPb(Br/I)3 QDs (~ 520 nm peak emission); FAPbBr3 QDs (~ 530nm peak emission); CsPb(Br/I)3 QDs (~ 650 nm peak emission); CsPbB QDs (~ 685nm peak emission), CdTe QDs (- 510 nm to 710 nm emission, when excited with UV-B or blue light); Zn-Cu-In-S/ZnS QDs, hydrophobic (~ 530 nm - 700 nm emission, when excited by UV-B or blue light); ZnCdSeS aQDs lloyed, hydrophobic ( - 470 nm - 630 nm emission when excited with UV-B or blue light), ZnCdSe/ZnS QDs hydrophobic 440-480nm (UV-B or blue excited); CdSe/ZnS hydrophobic 530- 650nm (UV-B or Blue excited); Perovskite Quantum Dots (QDs) can be used, configured to emit light in the entire visible spectral region from about 450 nm to about 690 nm when excited by UV-B or blue light output from the laser source with at high photoluminescence quantum yield up to 95-100 %; Lead Sulfide (PbS) QDs (800 nm - 1600 nm emission when excited with IR light)l CdSeTe/ZnS QDs ( 700 nm - 880 nm emission); as well as Blue CdS/ZnS & Blue/Green CdSSe/ZnS core shell quantum dots; CuInZnS/ZnS QDs ( 540 nm - 660 nm emission); and/or PbS/CdS near Infrared QDs (emission from about 900 nm to about 1,000 nm). Examples of sources of such photoluminescent materials include ACS Material LLC, USA; Shanghai Keyan Phosphor Technology Co., Ltd., China;

EnergyTech (Beijing) Co. Ltd, China; Edgetech Industries LLC, USA; Intematix, USA; PhosphorTech Corporation, USA, to name just a few.

[0073] As a skilled artisan will readily appreciate, one advantage of the present invention is its use of a high thermal conductivity material (such as CVD diamond, in one example) to abate thermal quenching of the phosphor component of the composite material. As a result, in one case high intensity laser excitation radiation such as 50 W optical power can be employed when utilizing a blue phosphor (such as

Ba2Lu5B5017:Ce3+) in the phosphor composite 124 to emit blue light - instead of relying on the blue light from an excitation source to bleed through the phosphor to provide the blue wavelength emission. When using a blue laser source, the use of coherent light can be problematic from an eye safety standpoint. By not relying on the excitation source to deliver blue light to the target, the phosphor or phosphor diamond composite of the present invention may be made as thick as necessary to achieve near full absorption of high- power excitation light without regard as to how much excitation light bleeds through to achieve the desired blue emission spectrum.

[0074] Selection of Source of Excitation Radiation and Auxiliary Components.

As was already allude to above, according to the idea of the invention, the excitation of the photoluminescent material component (phosphor) of the composite material 124 employed in PL cells of the present invention may be achieved with a light source configured to generate radiation at wavelengths in the range from about 250 nm to about 13,000 nm (the optimal excitation wavelength depends, of course, on the choice of the specific PL material component. In one embodiment, for example, a commercially available fiber-coupled UV-blue laser (configured to generate light in the spectral range from about 420 nm to about 450 nm) may be utilized. Alternatively or in addition, a commercially available (and optionally fiber-coupled) UV- blue laser (configured to generate light at wavelengths in the range from about 250 nm to about 520 nm) can be employed when the PL material component includes a phosphor operating by down conversion, and/or a commercially available and optionally fiber-coupled IR laser (wavelengths in the range from about 800 nm to about 1,100 nm) to effectuate the up-conversion in the phosphor, and/or a commercially available and optionally fiber-coupled IR laser in the range of selecting a excitation source in the range from about 800 nm to about 13,000 nm may be utilized.

[0075] In one specific example, a water-cooled 100 W fiber-coupled 450 nm blue laser (with an output 100 micrometer fiber, numerical aperture NA 0.22) may be used as the excitation source for a photoluminescent cell. The fiber cable exit end / facet is appropriately disposed, with or without focusing optics, to deliver laser light output onto and through the optically polished and preferably AR coated PL cell surface to form a spot of light of 1 mm or less in diameter at the encapsulated composite material 124 - see Fig. 1, for example - that contains about 70 weight-% of diamond particles and about 30 weight-% of phosphor (photoluminescent material) compressed together to form a composite "puck" that is about 1.5 mm in diameter and about 0.2 mm in thickness. The encapsulated thermally conductive material 124B may be generally present in the composite 124 in a range from about 1 weight percent to about 99.9 weight percent, or from 10 weight percent to about 99.9 weight percent, or from 20 weight percent to about 99.9 weight percent, or from 30 weight percent to about 99.9 weight percent, or from 40 weight percent to about 99.9 weight percent, or from 50 weight percent to about 99.9 weight percent, or from 60 weight percent to about 99.9 weight percent, or from 70 weight percent to about 99.9 weight percent, or from 80 weight percent to about 99.9 weight percent, or from 90 weight percent to about 99.9 weight percent, depending of the specific implementation.

[0076] A person of ordinary skill in the art will readily appreciate that one advantage provided by implementation of embodiment(s) of the present invention is that the dimensions of the composite material may be judiciously altered to facilitate the optical use of the excitation radiation and intensity of such radiation and efficiently convert it into incoherent PL light with the desired emission area for optimum optical manipulation.

[0077] It is appreciated that, preferably, each outer surface of an embodiment of a given PL cell that, in operation, is exposed to the ambient medium, may be appropriately coated with an AR think-film stack to reduce optical losses at at least one of the wavelength of excitation radiation and the wavelength of the PL light generated inside the cell.

[0078] To implement a heatsink, any of copper, aluminum, silver, gold, silicon carbide, aluminum nitride, boron nitride, aluminum silicon carbide, beryllium oxide, silicon-silicon carbide, aluminum silicon carbide, copper tungsten alloys, copper molybdenum carbides, carbon, diamond, graphite, and appropriate combinations may be used. The heatsink may be of vapor chamber or heat-pipe design, as recognized in related art. The heatsink may be configured to be cooled with liquid or gas (for example, air). The material selected for a heatsink may have thermal conductivity than 35 W/m-K, greater than 50 W/m-K, greater than 100 W/m-K, greater than 150 W/m-K, greater than 200 W/m-K, greater than 250 W/m-K, greater than 300 W/m-K, greater than 400 W/m-K, greater than 500 W/m-K, greater than 600 W/m-K, greater than 700 W/m-K, greater than 800 W/m-K, greater than W/m-K, greater than 1000 W/m-K, greater than 1500 W/m-K, or greater than 2000 W/m-K.

[0079] According to the idea of the invention, the use of a fiber optic element includes the use of a fiber with optical core/cladding diameters of about 9/125 microns, or 50/125 microns, or 62.5/125 microns, or a single material (only core) fiber lightpipe with a diameter of an optical potion of 100 microns, up to 200 microns, up to 400 microns, up to 600 microns, or even up to 1000 microns - depending on the specific implementation, while other sizes of the fiber optic element remain within the scope of the invention (based on the parameters of the exit optic and the desired cross-section of the excitation beam at the surface of the encapsulated composite material, as well as the distance separating the optics from such surface and the power of the excitation radiation). Fiber optic hardware connectors (not shown in Drawings) are mounted such that the polished facet of the corresponding fiber optic element is preferably in direct contact with the polished facet of the surface of a wall of the PL cell. Examples of such connectors include ST, LC, or FC connectors with UPC polish. The fiber element may be a hollow core element, an UV-stabilized fiber element, an UV-VIS fiber element, a micro-structured photonic crystal fiber: or glass-, poly-crystalline- and/or chalcogenide-based optical fiber element (the specific choice of which is made based on the wavelength of the excitation radiation, as well as target optical transmission losses in the fiber and desired power output).

[0080] In one specific example, a fiber optic element produced by Schott North America Inc., 122

Charlton Street, Southbridge, MA 01550, USA; and/or Coming Inc., Optical Communications, 800 17th St NW, Hickory, NC 28601, USA, can be used.

Use of Embodiments) of Invention for Enhancement of Plant Growth

[0081] In addition, embodiments of the invention address the persisting problem recognized in plant growth industry. The problem manifests in that waste heat from lighting sources employed for plant growth adds significantly to the cooling load inside the controlled environment agriculture (CEA) habitat as it would in any enclosed space, thereby substantially increasing operating costs and associated HVAC capital costs. It is well recognized in related industry that temperature of a given plant must be regulated to minimize evaporation losses and the unwanted closing of the stomata (which stops photosynthesis by restricting oxygen and carbon dioxide gas exchange) to achieve optimal growth and not cause stress on the plants.

[0082] Controlled-environment agriculture (CEA) is a technology-based intensive form of agriculture, used particularly for food production. The aim of CEA is to provide protection and maintain optimal growing conditions throughout the development of a crop. Production takes place within an enclosed growing structure such as a greenhouse, retrofitted warehouse, shipping container, and/or growth chambers of various configurations. Plants are often grown using hydroponic methods in order to supply the proper amounts of water and nutrients to the root zone. CEA optimizes the use of resources such as water, energy, space, capital and labor. CEA technologies may also include aquaculture, aeroponics and aquaponics. CEA is most suited for the production of high-value crops, such as perishable foods, herbs and spices, ornamentals, and medicinal compounds. CEA offers consistency of crop production through control systems that regulate variables of photon intensity, light spectral distributions, temperature, humidity, CO2, air exchange, growth media and fertilizer to maximize individual crop yields.

[0083] It has been demonstrated that moderate heat stress causes photo-inhibition of PSII that suppresses protein synthesis. The use of embodiments of the present invention allows the separation of the waste heat generated by the source of excitation radiation from the CEA (greenhouse) environment, thereby minimizing at least one source or cause of plant heat stress. Moreover, such use permits the skilled artisan to to combine different photoluminescent materials (via the implementation of the color-wheel type of embodiment, discussed above) so as to optimize the delivery to the plant(s) of PL output O at selected wavelengths, thereby removing excess of delivered PL that would otherwise contribute to waste heat and stimulated photo-inhibition to the detriment of the photosynthesis process.

[0084] Indeed, as discussed in reference to the examples of embodiments presented above, the photoluminescent materials contained in the volume of PL cell(s) or containers) can be physically/spatially separated from the source of excitation radiation, thereby preventing any waste heat from the power supply and/or source of excitation radiation from reaching the photoluminescent materials and contributing to thermal quenching and further reducing the cooling load on the environment, the cooling load inside the CEA environment is also reduced (as the waste heat is managed outside the CEA habitat) with corresponding power savings.

[0085] Photosynthesis (6CO2 + 6ELO + photon energy = G.H CL + 6O2) is a complex multistep process, that utilizes photon energy in the wavelength spectral range of approximately 320 nm to 800 nm to facilitate the reactions. In light dependent reactions, the electrons travel pathways to enzymes; photons hit the second pigment molecule allowing the enzymes to convert ADP to ATP and NADP+ to convert to NADPH. The reactions are catalyzed by soluble enzymes of the chloroplast stroma. The ATP and NADPH are used by the Calvin cycle as a power source for converting carbon dioxide from the atmosphere into simple sugar glucose. Thus various reactions involve atmospheric CO2 fixation and reduction of the fixed carbon into carbohydrate e.g. sugars such as fructose, glucose, lactose and starches. These ATP reactions are now also known to be indirectly stimulated by light energy.

[0086] Light capturing occurs in the adaxial (upper leaf surface) and gas exchange occurs in the abaxial (lower leaf surface). This division into adaxial and abaxial domains affects the outgrowth of the lamina (leaf edge), which occurs along the boundary between the adaxial and abaxial sides. The more photons of light fall on a leaf, the greater the number of chlorophyll molecules that are ionized and the more ATP (Adenosine 5 '-triphosphate, is the principal molecule for storing and transferring energy in cells) and NADPH (nicotinamide adenine dinucleotide phosphate hydrogen, is a product of the first stage of photosynthesis and plays a crucial role in these chemical reactions) are generated. As light intensity is increased further, however, the rate of photosynthesis is eventually limited by some other factor(s) to cause the rate plateaus. When very high light intensity is delivered to the plant, chlorophyll may be damaged and the rate of photosynthesis drops steeply. Chlorophyll a is used in both photosystems. The wavelength of light is also important. In general, PSI (Photosystem I, or plastocyanin-ferredoxin oxidoreductase, is one of two photosystems in the photosynthetic light reactions.) absorbs energy most efficiently at about 700 nm and PSII (Photosystem II, or water-plastoquinone oxidoreductase, is the first protein complex in the light-dependent reactions of oxygenic photosynthesis.) at about 680 nm, but various plants respond better to light in wider wavelength ranges. Light with a higher proportion of energy concentrated around these wavelengths deliver photosynthesis at a higher rate. An increase in the carbon dioxide concentration increases the rate at which carbon is incorporated into carbohydrate in the light-independent reaction, and so the rate of photosynthesis generally increases until limited by another factor.

[0087] Although the light-dependent reactions of photosynthesis are not necessarily affected by changes in temperature, the light-independent reactions of photosynthesis are known to depend on temperature. (These light-independent reactions are catalyzed by enzymes. As the enzymes approach their optimum temperatures the overall reaction rate increases. Such reaction rate approximately doubles for every 10 °C increase in temperature. Above the optimum temperature the rate begins to decrease, as enzymes are denatured.) Therefore, temperature of the plant environment is critical for growth optimization.

[0088] According to a 2017 U.S. Department of Energy report, LEDs make up just 2 to 4 percent of the lighting technology mix for U.S. supplemental CEA lighting (Source: K. Stober et al. (2017).“Energy savings potential of SSL in horticultural applications. Prepared for the U.S. Department of Energy Solid-State Lighting Program by Navigant Consulting Inc.”; available at - www.energy.gov/sites/prod/files/2017/12/f46/ssl_horticulture_dec2017.pdf).

[0089] The presence of favorable light environment is critical for optimal plant growth and development. Deficits of natural light in intensity and time limit the plant productivity, which in turn results in poor quantitative and qualitative yield. In order to mitigate insufficient light, artificial electrical lamps have been used as a reliable source of light for indoor cultivation. In the past, various conventional light sources including incandescent lamps, fluorescent lamps, high-pressure mercury, sodium and metal-halide lamps, as well as xenon arc and flash tubes have been employed for plant lighting in greenhouses and controlled cultivation facilities. Wall plug efficiency for these type lamps is generally 5-10%.

[0090] HID (High-intensity discharge lamps) lighting systems are often very hot and intense. Plants placed too close to these systems may be burned or oversaturated. In recent years, light-emitting diodes and phosphor coated LEDs have enhanced artificial plant lighting when compared to the earlier conventional light sources. Panels of emission from LED sources can be assembled to somewhat match the light requirement of the plant species that are being cultivated. Low power consumption and long lamp life span have make LED- based lamps a better choice than earlier technologies for plant growth than their predecessors offering lower heat emission, and smaller. Wall plug efficiency for these type LED lamps is about 15-20%.

[0091] LED-based light sources used for plant growth enhancement (while being cooler and more energy efficient that other sources of light) still suffer from certain drawbacks. For one, the remaining waste heat generation by LEDs continues to be a problem requiring auxiliary cooling where approximately 85% of the electrical energy input into LEDs is converted to waste heat. Venting the waste heat directly into the greenhouse results in increased load on greenhouse cooling means to maintain optimal growing conditions. Further, it was observed that LED-based plant growth light sources often emit less intense light at fewer wavelengths, and in a generally narrower spectral band than is optimal for plant growth. This,

understandably, causes plants to yield inferior quality, lower quantity or density and may also lower potency and flavor. LED light that is stray or wasted (which is the case where non-point source light cannot be optimally and uniformly projected onto the growing target canopy) does not impact the plants but continues to be a problem. Moreover, the same waste heat from the light emitting diode that which is closely coupled to the phosphor within an LED, can result in thermal quenching of the phosphors (the same problem stated above) and elevated LED junction temperatures, thereby decreasing light output as a result of inherent heat transfer cooling limitations in current designs. This inevitably reduces the amount of light that the conventional LED phosphor cell can be designed to produce.

[0092] Single LEDs dies are not sufficiently intense to achieve the highest energy micro-mol/m² required to push plant growth in an area of one square meter. To deliver more light, LED manufacturers have increased the light-emitting areas with arrays of LEDs in COB (known as "chip-on-board"; Chip on Board- Array of LED chips are tightly packaged together on one core board) configurations. Uniformity of light distribution within the targeted canopy area is not uniform, being more intense in the center and decreasing further from the center. The use of LED arrays allowed for increase of the overall light output, but as the light is no longer a virtual“point source of light”, such light cannot be efficiently focused or directed to the target without the generation of additional wasted stray light effectively increasing energy consumption for targeted light application. Current LED optics, due to the large area of LED phosphor emitters required to achieve desired levels and uniformity of photon energy, are not efficient at optimizing beam uniformity.

[0093] White light LEDs (manufactured by combining a blue-light emitting LED with yellow- and red-light emitting phosphors) rely on a certain spectral portion of the blue LED- generated light to escape through these phosphors to produce light with overall“white light” spectrum. This requires a carefully controlled deposition thickness and uniformity of the phosphor thickness, which is difficult to achieve. Therefore, manufacturers are producing these LED with a wide specification range even when sorting them by performance testing into narrower“bins”. The thickness of the phosphor coating produces variations in the color temperature of a given LED. In critical applications where the amount of light and frequency of the light can affect plant growth performance, these differences can be problematic both economically and in bringing a crop to harvest at the same time under LED lights, which perform differently. Over time, the blue LED die and the yellow phosphor are known to degrade, causing a shift in the spectrum of the output light and producing unexpected colors if the LED-based light source is operated at a current or operating temperature that differ from the nominal ones.

[0094] Recent attempt to use coherent laser light for enhancement of plant growth did not produce promising results and remains problematic due to the incompatibility of coherent laser light (for which neither plants and people have not been genetically adapted) with living organisms as well as human exposure risks factors.

[0095] Overall, most plant-growth light sources utilized to-date including LEDs, HID, and HPS

(High Pressure Sodium), do not generate light within the full spectrum required to meet the optimal needs of the plants being grown, and short arc lamps - while somewhat approximating the Sun’s spectral output within the photosynthesis range - deliver about half of the radiative output in the inconsequential for the plant growth IR spectral range, thereby wasting energy and generating unnecessary waste heat.

[0096] Accordingly, there remains a need for a more intense compact light source (which case be considered to be a substantially point source as perceived from the target plants) for use in the CEA habitat, such source configured to minimize wasted stray light upon delivery of light to the target plants and/or having improved uniformity of the light beam striking the plant canopy target and/or configured to minimize the waste heat generation over and above that achieved with the use of LED sources

[0097] The skilled artisan will readily appreciate that to solve these problems, embodiments of the present invention provide a method for efficient utilization of the laser light and/or LED light to produce high-intensity incoherent photoluminescent light output from phosphor-based composite materials contained within the cells / containers of the embodiments (such as those, discussed, for example, in reference to Figs.

1 through 14) while at the same time alleviating the problem of thermal quenching of the phosphor material components of these composite materials. Additionally or in the alternative, by positioning the power drivers of the sources of excitation radiation outside the growing environment, waste heat from these drivers are prevented from entering the plant growth environment.

[0098] To this end, the schematic illustrations discussed below illustrate such methodology. In particular:

[0099] Fig. 15 depicts a horticultural light source for manipulation of metabolism, growth and maturation of the plants 1510. The source is configured similarly to the structure of the embodiment of Fig.

12, and includes a laser source 1210 of excitation radiation, delivered through the fiber optic cable 1220 to the PL-cell-based source of photoluminescence (which in turn is configured according to any of the embodiments depicted in Figs. 1 through 10, for example). The remotely - from the plants 1510 - mounted laser excited photoluminescence cell of this implementation is thermally connected to a water or air cooled waste heatsink, as discussed above, and the incoherent excitation PL light O is directly delivered to plants 1510 to be benefited by such light emission. In related embodiments, the delivery of light from the PL cell of the horticultural light source to the plans can be facilitated by at least one of a lens and a fiber-optic element - by analogy with the structure of the embodiment shown in Fig. 11, for example - inserted between the PL cell and the target plants 1510. Alternatively or in addition, the target plants can be irradiated with PL light from multiple PL cells - the PL cells being irradiate from a single or multiple sources of excitation radiation. (Notably, in this latter case multiple optics 1620 may be required.)

[00100] Fig. 16 illustrates a related embodiment, in which a horticultural light source of Fig. 15, combined with stray-light recycling retroreflector 1610 and optics 1620 configured according to teachings of US 7,979,204, US 8,388,190 and/or US 8,317,331, utilizes the laser excitation radiation delivered to at least one PL cell from the rear side of the PL cell(s) that is opposite the wall(s) of the PL cell(s) through which the incoherent PL light O is emitted and directed to multiple plants 1510 to be benefited by such light emission. (Notably, and as a skilled artisan will readily appreciate, in implementations where multiple PL cells are used instead of a single PL cell to generate PL light output O, multiple optics 1620 may be required.)

Alternatively or in addition, the excitation radiation can be delivered through the fiber optic element 1220 from the laser source 1210 to the PL cell from the front wall of the PL cell.

[00101] Fig. 17 depicts a related embodiment of the horticultural light source, structured similarly to the source of Fig. 16. Here, the excitation radiation is delivered through the fiber optic element(s) 1220 from the laser source(s) 1210 to at least one PL cell from the rear, and each of the used PL cells employs two light- recycling retroreflectors - 1708, 1610. Such configuration may be used when the embodiment of the utilized PL cell(s) is structured by analogy with that of Fig. 6, for example, in which the photoluminescence generated by the composite material 124 is delivered from the PL cell through both optically-transmissive walls exposed to the ambient, that is in both directions along the PL cell’s axis 536 (indicated in Fig. 6). The retroreflector 1708 is configured to recycle stray excitation radiation and PL light emitted from the rear side of the PL cell by redirecting these light fluxes towards the composite material 124 within the PL cell. The retroreflector 1708 may be configured, for example, according to teachings of US 7,979,204, US 8,388,190, and US 8,317,331. (Notably, and as a skilled artisan will readily appreciate, in implementations where multiple PL cells are used instead of a single PL cell to generate PL light output O, multiple optics 1620 may be required.)

[00102] Understandably, in each of the above-discussed implementations, the system may additionally employ an appropriately configured fiber optic element transferring the PL light O from the PL cell across a distance separating the PL cell from the plants 1510 (by analogy with the schematic of Fig. 11. The collection and re-shaping of spatial distribution of the PL light O, generated by any of the embodiments of the invention, is greatly facilitated by the fact that the PL cells are dimensioned to represent very spatially- small sources (approximating the point sourced) as compared with spatially-broad LED-based source currently used in horticulture.

[00103] A skilled artisan will readily appreciate, therefore, that embodiments of the invention provide a use of a light source configured to reduce heat stress of a plant in CEA environment. Here, the light source includes a PL cell, a laser excitation source (with appropriate power source or driver to operate the laser excitation source) that is optically coupled to the PL cell. The use includes: a) delivering excitation radiation from the laser excitation source, disposed with the power source outside of the CEA environment, to the PL cell through a fiber-optic element; b) irradiating a composite material enclosed in the PL cell with the excitation radiation to generate PL light at a chosen wavelength in a spectral range from about 280 nm to about 13,000 nm (here, the composite material includes a combination of a photoluminescent material and a filler material; the photoluminescent material is configured to generate the PL light; and the filler material is substantially optically-transmissive at said wavelength and has thermal conductivity of at least 30 W/m-K; c) at least partially transmitting the PL light through a wall of the PL cell (the wall includes a wall material that is substantially optically-transmissive at the chosen wavelength and has thermal conductivity of at least 30 W/m-K); and d) irradiating the plant with output PL light that has been at least partially transmitted through said wall. The process of irradiating may include generating the PL light while at the same time reducing thermal quenching of the photoluminescent material in the composite material. In substantially any implementation, the PL cell is preferably located outside (very remotely to) the CEA environment and the process of irradiating the plant includes delivering the output PL light to the plant with the use of an auxiliary fiber optic element. Alternatively or in addition, the laser excitation source may be operated a pulsed regime characterized by at least one of (pulse frequency between 20 kHz and 70 kHz; pulse duration between 10⁵ and 10 ³ second; and duty cycle of about 30%) in order to cause residual waste heat delivered to the plant to dissipate when a laser pulse is off). In substantially any implementation, the use of the light source may be configured such that at least one of the following conditions is satisfied: a) the wall material and the filler material include at least one of synthetic diamond, CVD diamond, polycrystalline diamond, monocrystalline diamond, sapphire, cubic boron arsenide, gallium arsenide, gallium phosphide, and gallium nitride; b) the wall material and the filler material are the same material; c) at least one of the wall material and the filler material has a thermal conductivity value within a range from about 500 W/m-K to about 2,000 W/m-K; d) the photoluminescent material includes at least one of a phosphor-based light emitting material, a nanotube, a light-emitting nanocrystal, a fluorescent nano-diamonds, a doped waveguides and/or light pipes, a doped diamond, a doped crystal, a quantum dot, and a scintillator; e) the filler material includes first material particles with an average size between 2 microns and 30 microns; and f) the filler material includes second nano-sized material particles (that is particles dimensioned to be smaller than one micron across). Additionally or in the alternative, and substantially in any implementation, at least one of the following conditions may be satisfied: (i) the use comprises at least one of (il) transferring thermal energy between the composite material and an ambient medium surrounding the PL cell through a heatsink disposed in contact with the PL cell; (i2) transferring the thermal energy between the composite material and the ambient medium through a heatsink element disposed to fittingly grasp a flange of the PL cell from first and second sides of the flange, the flange protruding from an axis of the container and being devoid of the composite material; and (i3) transferring thermal energy between the composite material and the ambient medium through a heat-pipe; (ii) the process of irradiating includes delivering the excitation radiation through a channel in the heatsink; (iii) the process of irradiating includes delivering the excitation radiation from the laser excitation source through an optical element that is in contact with the PL cell; and (iv) the process of irradiating includes delivering the excitation radiation from at least one of the laser excitation source, a light emitting diode (LED), and an optical fiber element.

Additional Considerations for Embodiments Employed for Plant Growth.

[00104] The graphs presented in Fig. 18 illustrate the primary wavelengths of light absorbed by plants for photosynthesis. Fig. 19 shows a more detailed absorption spectrum required for plant growth, indicating a need is utilizing composite phosphors for use in the PF (photoluminescent light ) cells of the embodiments of the invention to generate PF light benefiting plant growth in a much broader range (390 nm - 740 nm) than that utilized in related industry at this time.

[00105] Photosynthesis is far more complex and involves many other chemicals like carotene and xanthophyll. A color spectrum of light absorbed by the whole leaf shows that plants actually use a much wider range of wavelengths, including green and yellow. Plants use light mostly for photosynthesis and this is done by specific chemicals in the leaves. In the plant light absorption spectrum graph (Fig. 19) one can clearly see the large peaks in the blue and red regions showing which colors, specifically Chlorophyll A and B are most used for photosynthesis. In addition, phycocyanin is a pigment-protein complex from the light- harvesting phycobiliprotein family, along with allophycocyanin and phycoerythrin. They are accessory pigments to chlorophyll.

[00106] Plants, which use sunlight for photosynthesis and are unable to avoid exposure to elevated levels of UV-B radiation (280 nm - 320 nm, due to ozone layer damage), are at risk. UV-B radiation significantly reduces photosynthesis rates and quantum yield damaging the plant and causing mutations. Damage cause by UV-B light can be reduced by high PAR (photosynthetic active radiation: from about 400 nm to about 700nm) and UV-A (320 nm - 390nm) radiation levels (which indirectly increases leaf thickness and the concentration of flavonoids and other phenolic compounds known to be important in UV screening). [00107] UV-A violet light (320 nm - 400 nm) has relatively high energy, and can have an effect on plant growth and in some species enhances flowering. Control intensity since light in this wavelength may either enhance or stunt plant development in certain Species and Varieties. The use of light within this spectral range facilitates thickening of plant leaves and promotes pigmentation.

[00108] Light visually perceived as blue and/or cyan in color (approximately 400 nm - 500 nm) affects the chlorophyll content present in the plant as well as leaf thickness. This light has relatively high energy and causes pronounced effects on plant growth and flowering as well as regulating the opening of stomata that control both water loss and carbon dioxide uptake. The use of light in this spectral region facilitates thickening of plant leaves and promotes pigmentation. Plants grown with blue light are usually shorter and have smaller, thicker and darker green leaves as compared to plants grown without blue light.

[00109] Light visually perceived as blue-green light (approximate spectral range of 500 nm - 535 nm) has been reported to increase root and plant growth. Increased growth rate occurred at 300 PPFD (photosynthetic photon flux density) indicated that green light at high intensity facilitates morphogenesis and photosynthesis.

[00110] Green-yellow light (about 535 nm - 600 nm) is widely reported to make substantially no contribution to photosynthesis since such light is generally reflected by the plant and is not absorbed. Such observations and conclusions are not necessarily correct, however: according to some reports, green light penetrates through thick top canopies to support leaves in the lower canopy. A study showed that green light resulted in fewer fixations in the upper epidermal layer (guard cells) and upper most palisade mesophyll compared to red and blue light, but resulted in more fixations deeper in the leaf than that caused by either red or blue light. In strong white light, the quantum yield of photosynthesis would be lower in the upper chloroplasts, located near the illuminated surface, than that in the lower chloroplasts. (Source: Jindong Sun, John N. Nishio and Thomas C. Vogelmann, "Green Light Drives C02 Fixation Deep within Leaves", Department of Botany, University ofWyoming, Laramie, Wyoming 82071-3165, U.S.A. Plant Cell Physiol. 39(10): 1020-1026 (1998)). But, because green light can penetrate further into the leaf than red or blue light, in strong white light, any additional green light absorbed by the lower chloroplasts would increase leaf photosynthesis to a greater extent than that caused by additional red or blue light. Thus, the use of green- yellow light can be beneficial for plant growth.

[00111] Orange-red light (approximate spectral range of 630 nm - 690 nm) is essential for the growth of stems, as well as the expansion of leaves. Light at these wavelengths also increases blooming, flowering/bud onset, dormancy periods, and seed germination. Chlorophyll absorption peaks at about 642 nm and about 667 nm. Light at certain specific red wavelengths is known to increase the production of hormones in a plant’s vegetation, which prevents the breakdown of chlorophyll. [00112] Red light within the spectral band from about 700 nm to about 740 nm also

transmits/penetrates through dense upper canopies to support the growth of leaves located lower on the plants. In addition, exposure to this far red light reduces the time a plant needs to flower. Another benefit of dark-red light is that plants exposed to this it tend to produce larger leaves than those not exposed to light in this spectrum. Emerson Enhancement Effect-simultaneously red and far red light increases photosynthesis.

[00113] Understandably, the appropriate color spectrum of light to be used for plant growth depends on the crop yield goals. As plants mature and go through their growth cycle from seedling, to adult, and then flowering and fruiting they use different color spectrums so the ideal light spectrum is different for each stage of growth. The ideal spectrum also varies by plant and plant variety to be grown. In general, while plants do best with light across all wavelengths, they do not require equal amounts of energy for each spectrum range. Therefore, experimentation or utilization of results of prior studies (indicating which wavelengths and spectral intensities across the range and at the different stages during the specific plant’s growth cycle are preferred to maximize growth and crop yield with the least energy consumption) may be required in the commercial setting.

[00114] Specific embodiments of the present invention may be configured to deliver pulsed PL light to the plants employing the pulsed source of excitation radiation L - such as laser sources 1210 of Figs. 12-16, for example operating at selected pulse frequencies - in one example, between about 2,000 Hz and about 70,000 Hz, with pulse duration in the range of 0.00001 second to about 0.0001 second. (Source: Michio Kanechi (September 19th 2018). Growth and Photosynthesis under Pulsed Lighting, Photosynthesis - From Its Evolution to Future Improvements in Photosynthetic Efficiency Using Nanomaterials, Juan Cristobal Garcia Canedo and Gema Lorena Lopez Lizarraga, IntechOpen, DOI: 10.5772/intechopen.75519; available at www.intechopen.com/books/photosynthesis-from-its-evolution-to-future-improvements-in-photosynthetic- efificiency-using-nanomaterials/growth-and-photosynthesis-under-pulsed-lighting) and other sources) The particular advantage sought after from the use of pulsed light at high intensity is that the PL light generated in the PL cell of an embodiment of the invention during the“on” dwell time drives the chemical reactions of photosynthesis within the plant at a more rapid reaction rate, but at the same time allows the waste heat to dissipate within the plant to the environment during the pulse“off’ dwell time. A targeted 33% duty cycle is preferred, while other duty cycles can be used (for example, about 30%, or generally 1% and 99%, or between 10% and 90%, or between 20% and 80%, to name just a few). The control of the excitation radiation source laser is preferably configured to allow for variable frequency, power setting, and/or dwell time control. Higher light application intensities are known to increase leaf thickness and the use of green light deep within the leaf.

[00115] Generally, and while not expressly shown in the Drawings, the chosen laser source of excitation radiation may be equipped with a remotely programmable microcontroller (electronic circuitry) configured for controlling the excitation source laser and thus spectral emissions in a desired manner, program code loaded on tangible non-transitory memory operably cooperated with such microcontroller and configured to drive the operation of the system of the embodiment of the invention (including the operation of, for example, the excitation laser source and any optical detector with which the embodiment may be used as well as a graphic user interface for an operator input to the system). The specific implementation of the control circuit of the excitation laser source may include electronic circuitry configured to detect plant heat and associated laser power control circuit configured to regulate at least one of power and duty cycle of the excitation laser source output so as to avoid heat stressing the plants beyond desirable limits pre-determined for the individual crop.

[00116] In one specific implementation of an embodiment of the invention, the amount of output emission O from the photohiminescent cell is directed on to the plants 1510 is controlled or adjusted by, for example, raising and/or lowering the light fixture containing the PL cell over the plant 1510, and/or changing the current feeding the excitation laser source 1210, and/or changing the duty cycle of the pulse trains produced by the excitation laser source, and/or changing the PWM (Pulse Width Modulation) of the excitation laser source, and/or changing the spatial spread and/or distribution of the emission O with the use of a zoom lens.

Examples of Additional Use of Embodiments of Invention: Billboards and Displays, Illumination of Buildings, Etc.

[00117] A lighting methodology similar to that discussed above in reference to Figs. 15-17 can be employed for backlit billboards and displays, where the photoluminescent cells are powered or excited by laser excitation delivered through fiber optic elements (instead of using electrical power delivered to the display/billboard fixture via a wire). In such embodiments the PL cells may be located remotely from the chosen fixture and the incoherent PL light delivered through the fiber optic cable or waveguide, to illuminate the image; or , alternatively, mounted behind the fixture and excited by remotely-located coherent laser light transmitted via fiber optics or waveguides.

[00118] To this end, Fig. 20 depicts a system employing a single source of excitation radiation 1210

(preferably, a laser source) the excitation radiation output from which is delivered to PL cells 2020 via fiber optics 2030 to excite the composite material 124 (not shown) contained in the volumes of the cells. The PL output O is further transferred to backlight the display(s)/billboards 2040 (with backlit materials such as vinyl, PET, polyethylene, polyester fabric and PVC materials). Optics 2042 and/or light diffusers 2044 may be utilized to appropriately shape the beam and ensure that spatial uniformity of beam irradiance.

[00119] Fig. 21 depicts a lighting system for a building 2160, configured with the use of sources of

PL light 2150 (each of which can be configured according to one of the embodiments of Figs. 1 through 14, for example) and operationally similar to the remote multiple horticultural growth plant lighting system(s) of Figs. 15, 16, 17. The split fiber optic transmission cable 2030 deliver excitation radiation to the photoluminescent cells of the sources 2150. The preferred light excitation source 2010 is a laser configured to generate light at about 450 nm wavelength or a wavelength of about 1,050 nm.

[00120] A skilled artisan appreciates therefore, that embodiments of the invention provides the use of a light source for illumination of a target surface, the light source containing a PL cell, a laser excitation source optically coupled to the PL cell, and a power source of the laser excitation source. The use includes: delivering excitation radiation from the laser excitation source, disposed with the power source outside of the CEA environment, to the PL cell through a fiber-optic element; and irradiating a composite material enclosed in the PL cell with the excitation radiation to generate PL light at a wavelength in a spectral range from about 280 nm to about 13,000 nm. (Here, the composite material includes a combination of a photoluminescent material and a filler material, the photoluminescent material is configured to generate said PL light, and the filler material is substantially optically-transmissive at said wavelength and has thermal conductivity of at least 30 W/m-K). The use also includes at least partially transmitting said PL light through a wall of the PL cell, wherein such wall includes a wall material that is substantially optically-transmissive at said wavelength and has thermal conductivity of at least 30 W/m-K; and further includes irradiating the target surface with output PL light that has been at least partially transmitted through the wall, wherein the target surface includes a wall or floor or ceiling or a back side of a display screen. In a specific case, the use also includes transmitting light, emanating from the display screen as a result of the irradiating the target surface, through an optical diffuser.

[00121] Other applications for photoluminescent cell-based lights sources of the present invention comprise light bulbs, backlight displays, bill boards, instrument panel illumination, entertainment lighting, hazardous area lighting, downhole lighting, laser projectors, search lights, automotive lights, underwater lights, medical device lighting, building lighting, power over fiber which each require high intensity or highly focused light beams.

[00122] When required, and whether or not shown explicitly in the drawings, an embodiment of the invention may include a programmable processor (electronic circuitry) controlled by instructions stored in a tangible, non-transitory memory. The memory may be random access memory (RAM), read-only memory (ROM), flash memory or any other memory, or combination thereof, suitable for storing control software or other instructions and data. Those skilled in the art should readily appreciate that, for example, operation of an embodiment of the invention may require the use of such programmable processor - for example, for operation of a source of excitation radiation irradiating a given PL cell, or the operation of a color wheel employing multiple PL cells. Such and other functions, operations, decisions, etc. may be implemented as computer program instructions, software, hardware, firmware or combinations thereof. Those skilled in the art should also readily appreciate that instructions or programs defining the functions of the present invention may be delivered to a processor in many forms, including, but not limited to, information permanently stored on non-writable storage media (e.g. read-only memory devices within a computer, such as ROM, or devices readable by a computer I/O attachment, such as CD-ROM or DVD disks), information alterably stored on writable storage media (e.g. floppy disks, removable flash memory and hard drives) or information conveyed to a computer through communication media, including wired or wireless computer networks. In addition, while the invention may be embodied in software, the functions necessary to implement the invention may optionally or alternatively be embodied in part or in whole using firmware and/or hardware components, such as combinatorial logic, Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs) or other hardware or some combination of hardware, software and/or firmware components.

[00123] References throughout this specification to "one embodiment," "an embodiment," "a related embodiment," or similar language mean that a particular feature, structure, or characteristic described in connection with the referred to "embodiment" is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. It is to be understood that no portion of disclosure, taken on its own and in possible connection with a figure, is intended to provide a complete description of all features of the invention. Within this specification, embodiments have been described in a way that enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without parting from the scope of the invention. In particular, it will be appreciated that all features described herein may be applicable to all aspects of the invention. Shown embodiments can be variably modified to better achieve goals of the invention. For example, as shown in Fig. 22 in a cross-sectional view, the delivery of excitation radiation L to the embodiment 500 of the PL cell of Fig. 5 can be carried out with the use of an optical-fiber excitation cable 2210 terminated with a glass tube 2214 (directing the radiation L through the layer 428 towards the composite material 124). Optionally, not only the layer 428 in this case can be dimensioned to accept at least the end of the tube 2214, but also be appropriately configured to redistribute the excitation radiation emanating from the tube 2214 such as to enhance the spatial uniformity of the emitted light O as necessary for the optical design of the lighting fixture by one skilled in the art.

[00124] When the present disclosure describes features of the invention with reference to corresponding drawings (in which like numbers represent the same or similar elements, wherever possible), the depicted structural elements are generally not to scale, and certain components are enlarged relative to the other components for purposes of emphasis and understanding. It is to be understood that no single drawing is intended or can be devised to support a complete description of all features of the invention. In other words, a given drawing is generally descriptive of only some, and generally not all, features of the invention. A given drawing and an associated portion of the disclosure containing a description referencing such drawing may not, generally, contain all elements of a particular view or all features that can be presented is this view, at least for purposes of simplifying the given drawing and discussion, and directing the discussion to particular elements that are featured in this drawing. A skilled artisan will recognize that the invention may possibly be practiced without one or more of the specific features, elements, components, structures, details, or characteristics, or with the use of other methods, components, materials, and so forth. Therefore, although a particular detail of an embodiment of the invention may not be necessarily shown in each and every drawing describing such embodiment, the presence of this particular detail in the drawing may be implied unless the context of the description requires otherwise. In other instances, well known structures, details, materials, or operations may be not shown in a given drawing or described in detail to avoid obscuring aspects of an embodiment of the invention that are being discussed. Furthermore, the described single features, structures, or characteristics of the invention may be combined in any suitable manner in one or more further embodiments.

[00125] Moreover, if the schematic flow chart diagram is included, the depicted order and labeled steps of the logical flow are indicative of one embodiment of the presented method. Other steps and order of steps may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated method. Without loss of generality, the order in which processing steps or particular methods occur may or may not strictly adhere to the order of the corresponding steps shown.

[00126] For the purposes of this disclosure and the appended claims, the use of the terms

"substantially", "approximately", "about" and similar terms in reference to a descriptor of a value, element, property or characteristic at hand is intended to emphasize that the value, element, property, or characteristic referred to, while not necessarily being exactly as stated, would nevertheless be considered, for practical purposes, as stated by a person of skill in the art. These terms, as applied to a specified characteristic or quality descriptor means "mostly", "mainly", "considerably", "by and large", "essentially", "to great or significant extent", "largely but not necessarily wholly the same" such as to reasonably denote language of approximation and describe the specified characteristic or descriptor so that its scope would be understood by a person of ordinary skill in the art. The use of this term in describing a chosen characteristic or concept neither implies nor provides any basis for indefiniteness and for adding a numerical limitation to the specified characteristic or descriptor. As understood by a skilled artisan, the practical deviation of the exact value or characteristic of such value, element, or property from that stated may vary within a range defined by an experimental measurement error that is typical when using a measurement method accepted in the art for such purposes. For example, the terms "approximately" and about", when used in reference to a numerical value, represent a range of plus or minus 20% with respect to the specified value, more preferably plus or minus 10%, even more preferably plus or minus 5%, most preferably plus or minus 2%.

[00127] The invention as recited in claims appended to this disclosure is intended to be assessed in light of the disclosure as a whole, including features disclosed in prior art to which reference is made. Furthermore, disclosed aspects, or portions of these aspects, may be combined in ways not listed above. Accordingly, the invention should not be viewed as being limited to the disclosed embodiment(s).

Claims

CLAIMS What is claimed is:

1. An article of manufacture comprising:

a container having a volume and an outer wall containing a first material that is substantially optically-transmissive at a wavelength in a spectral range from about 280 nm to about 13,000 nm and that has a thermal conductivity of at least 30 W/m-K;

a composite material contained in said volume and including a combination of a photoluminescent material and a second material,

wherein the photoluminescent material is configured to generate photoluminescent light at the wavelength,

wherein the second material is substantially optically-transmissive at the wavelength and has said thermal conductivity.

2. The article of manufacture according to claim 1, wherein said combination includes one of

i) a mixture or blend of particles of the photoluminescent material and particles of the second material; and

ii) a layered structure including alternating first and second layers, the first layer containing the photoluminescent material and the second layer containing the second material.

3. The article of manufacture according to claim 1, comprising at least one of

a heatsink in thermal contact with said container; and

an excitation source configured to deliver excitation radiation to the composite material, and configured as a source of light.

4. The article of manufacture according to claim 3, wherein at least one of the following conditions is satisfied:

a) the container is dimensioned to include a flange radially protruding from an axis of the container and devoid of the composite material, wherein the heatsink includes a heatsink element grasping or clamping the flange from first and second sides;

b) the heatsink includes a channel therethrough dimensioned to transmit said excitation radiation to the container;

c) the heatsink is in thermal contact with a heat-pipe; and d) the excitation source includes at least one of a laser, a light emitting diode (LED), and an optical fiber element.

5. The article of manufacture according to claim 3, wherein the composite material is in direct physical contact directly on the heatsink, and the heatsink is in direct physical contact with said oute wall.

6. The article of manufacture according to one of claims 1, 2, 3, and 4, wherein at least one of the following conditions is satisfied:

a) the volume is a volume of a hollow in said container, wherein an aperture defined by the hollow is covered with a lid layer;

b) the lid layer contains a lid material that is substantially optically-transmissive at said wavelength and that has said thermal conductivity;

c) the lid layer includes said excitation source;

d) the lid layer is fluidly sealing said aperture; and

e) the first and second materials are the same material.

7. The article of manufacture according to one of claims 1, 3, 4, and 5, wherein the composite material includes sintered composite material.

8. A color wheel light source comprising:

a wheel substrate configured to rotate about an axis of the wheel substrate;

a plurality of articles of manufacture, each configured according to one of claims 1 through 6 and disposed circumferentially on a surface of the wheel substrate in a peripheral region thereof in thermal contact with the wheel substrate, and

a fan centered and rotating about said axis of the wheel substrate,

wherein the wheel substrate is configured as an auxiliary heatsink in thermal contact with at least one of a heatsink and a container of each of the plurality of said articles of manufacture.

9. A method for operating an article of manufacture that comprises

a container having a volume and an outer wall containing a first material that is substantially optically-transmissive at a wavelength in a spectral range from about 280 nm to about 13,000 nm and that has a thermal conductivity of at least 30 W/m-K; a composite material contained in the volume and including a combination of a photoluminescent material and a second material,

wherein the photoluminescent material is configured to generate photoluminescent light said wavelength, and

wherein the second material is substantially optically-transmissive at said wavelength and has said thermal conductivity,

the method comprising:

irradiating the composite material with excitation radiation to cause the composite material generate photoluminescent light at the wavelength; and

at least partially transmitting said photoluminescent light through the outer wall.

10. The method according to claim 9, wherein said irradiating includes one of

i) irradiating a mixture or blend of particles of the photoluminescent material and particles of the second material; and

ii) at least partially transmitting the excitation radiation through a layered structure including alternating first and second layers, the first layer containing the photoluminescent material and the second layer containing the second material.

11. The method according to one of claims 9 and 10, wherein at least one of the following conditions is satisfied:

a) transferring thermal energy between the combination and an ambient medium through a heatsink disposed in contact with said container;

b) transferring thermal energy between the combination and the ambient medium through a heatsink element dimensioned to fittingly grasp a flange of the container from first and second sides of the flange, the flange protruding from an axis of the container and being devoid of the composite material;

c) transferring thermal energy between the combination and the ambient medium through a heat- pipe;

d) wherein said irradiating includes delivering said excitation radiation through a channel in said heatsink;

e) wherein said irradiating includes delivering the excitation radiation from a source of said excitation radiation that is in contact with the combination; and

f) wherein said irradiating includes delivering the excitation radiation from at least one of a laser, a light emitting diode (LED), and an optical fiber element.

12. The method according to one of claims 9, 10, and 11, wherein at least one of the following conditions is satisfied:

c) the lid layer includes said excitation source;

d) the lid layer is fluidly sealing said aperture; and

e) the first and second materials are the same material.

13. The method according to one of claims 9 through 12, comprising:

rotating a wheel substrate about an axis of the wheel substrate, the wheel substrate comprising more than one of said article of manufacture that are disposed circumferentially on a surface of the wheel substrate in a peripheral region thereof in thermal contact with the wheel substrate, wherein the wheel substrate is configured as an auxiliary heatsink in thermal contact with at least one of a heatsink and a container of each of the plurality of said articles of manufacture,

and

transferring thermal energy between the wheel substrate and the ambient medium by operating a fan centered and rotating about said axis of the wheel substrate.

14. The method according to one of claim 9 through 13, comprising irradiating at least one of a plant, a backside of a display screen, and a surface of a building with said photoluminescent light that has been at least partially transmitted through the outer wall.

15. The method according to claim 9, comprising

irradiating a target with said photoluminescent light that has been at least partially transmitted through the outer wall, and

generating said excitation radiation by operating a laser excitation source in one of a continuous wave (CW) fashion and a pulsed fashion, wherein when the target is a plant, said pulsed fashion characterized by at least one of:

- pulse frequency between 20 kHz and 70 kHz;

- pulse duration between 10⁵ and 10 ³ second; and

- duty cycle of about 30% to allow waste heat delivered to the plant to dissipate when a laser pulse is off.

16. Use of a light source for reducing heat stress of a plant in controlled environment agriculture (CEA) environment, the light source comprising a photoluminescent (PL) cell, a laser excitation source optically coupled to the PL cell, and a power source of the laser excitation source, the use comprising:

delivering excitation radiation from the laser excitation source, disposed with the power source outside of the CEA environment, to the PL cell through a fiber-optic element;

irradiating a composite material enclosed in the PL cell with the excitation radiation to generate PL light at a wavelength in a spectral range from about 280 nm to about 13,000 nm,

wherein the composite material includes a combination of a photoluminescent material and a filler material,

wherein the photoluminescent material is configured to generate said PL light, and wherein the filler material is substantially optically-transmissive at said wavelength and has thermal conductivity of at least 30 W/rn-K; at least partially transmitting said PL light through a wall of the PL cell, wherein said wall includes a wall material that is substantially optically-transmissive at said wavelength and has thermal conductivity of at least 30 W/m-K; and irradiating the plant with output PL light that has been at least partially transmitted through said wall.

17. The use according to claim 16, wherein said irradiating includes generating said PL light while at the same time reducing thermal quenching of the photoluminescent material in said composite material.

18. The use according to one of claims 16 and 17, wherein the PL cell is located outside the CEA environment and said irradiating the plant includes delivering said output PL light to the plant with the use of an auxiliary fiber optic element.

19. The use according to claim 16, comprising operating the laser excitation source in a pulsed fashion characterized by at least one of:

- pulse frequency between 20 kHz and 70 kHz;

- pulse duration between 10⁵ and 10 ³ second; and - duty cycle of about 30%

to allow waste heat delivered to the plant to dissipate when a laser pulse is off.

20. The use according to one of claims 16, 17, and 19, wherein at least one of the following conditions is satisfied:

a) the wall material and the filler material include at least one of synthetic diamond, CVD diamond, polycrystalline diamond, monocrystalline diamond, sapphire, cubic boron arsenide, gallium arsenide, gallium phosphide, and gallium nitride;

b) the wall material and the filler material are the same material;

c) at least one of the wall material and the filler material has a thermal conductivity value withi a range from about 500 W/m-K to about 2,000 W/m-K;

d) the photoluminescent material includes at least one of a phosphor-based light emitting material, a nanotube, a light-emitting nanocrystal, a fluorescent nano-diamonds, a doped waveguides and/or light pipes, a doped diamond, a doped crystal, a quantum dot, and a scintillator;

e) the filler material includes first material particles with an average size between 2 microns and 30 microns;

f) the filler material includes second nano-sized material particles.

21. The use according to one of claims 16, 17, and 19, wherein at least one of the following conditions is satisfied: a) the use comprises at least one of

- transferring thermal energy between the composite material and an ambient medium surrounding the PL cell through a heatsink disposed in contact with said PL cell;

- transferring said thermal energy between the composite material and the ambient medium through a heatsink element disposed to fittingly grasp a flange of the PL cell from first and second sides of the flange, the flange protruding from an axis of the container and being devoid of the composite material;

- transferring thermal energy between the composite material and the ambient medium through a heat-pipe; b) wherein said irradiating includes delivering said excitation radiation through a channel in said heatsink;

c) wherein said irradiating includes delivering the excitation radiation from the laser excitation source through an optical element that is in contact with the PL cell; and d) wherein said irradiating includes delivering the excitation radiation from at least one of the laser excitation source, a light emitting diode (LED), and an optical fiber element.

22. Use of a light source for illumination of a target surface, the light source comprising a photoluminescent (PL) cell, a laser excitation source optically coupled to the PL cell, and a power source of the laser excitation source, the use comprising:

wherein the photoluminescent material is configured to generate said PL light, and wherein the filler material is substantially optically-transmissive at said wavelength and has thermal conductivity of at least 30 W/rn-K; at least partially transmitting said PL light through a wall of the PL cell, wherein said wall includes a wall material that is substantially optically-transmissive at said wavelength and has thermal conductivity of at least 30 W/m-K; and irradiating the target surface with output PL light that has been at least partially transmitted through said wall, wherein the target surface includes a wall or floor or ceiling or a back side of a display screen.

23. The use according to claim 22, comprising

transmitting light, emanating from the display screen as a result of said irradiating the target surface, through an optical diffuser.