WO2021016119A1

WO2021016119A1 - Emitter array and light combiner assembly

Info

Publication number: WO2021016119A1
Application number: PCT/US2020/042647
Authority: WO
Inventors: Kevin Tabor; Paige Higby; Scott RASZKA
Original assignee: Schott Corporation
Priority date: 2019-07-19
Filing date: 2020-07-17
Publication date: 2021-01-28

Abstract

An ordered emitter array includes a plurality of micro-emitters configured to emit light. A light combiner configured as a partially fused optical fiber bundle has opposed bundle input and outputs ends between which there extends a plurality of constituent optical fibers. Each optical fiber has opposed light-input and light-output ends coinciding with, respectively, the bundle input and output ends. The light-input end of each optical fiber is aligned with a micro-emitter. Collectively, the light-input ends define a combiner input array having an input-array density indicative of the quantity of light-input ends per unit area, while the light-output ends define a combiner output array having an output-array density indicative of the quantity of light-output ends per unit area. While the diameter of each optical fiber remains constant, the optical fibers collectively taper such that the output-array density is higher than the input-array density.

Description

EMITTER ARRAY AND LIGHT COMBINER ASSEMBLY

BACKGROUND

Currently, laser targeting systems use single mode edge emitting lasers with a 1x3 micron format and an approximate 35-degree field of illumination. These single mode edge emitters provide relatively tight beam profiles with adjustable divergence, low etendue, and a compact size. However, single mode edge emitters have significant issues with so-called“speckle” and uniformity of the beam profile.

In order to obviate the speckle and uniformity issues associated with single mode edge emitters, their substitution with light-emitting diodes (LEDs) has been attempted. While LEDs offer improvements in the speckle and beam-uniformity aspects associate with single mode edge emitters, LEDs present issues of their own, including low power density, large formats that require too much space in a packaging“can,” and the inability to adjust divergence.

Vertical cavity side emitting lasers (VCSELs) offer compact packaging, low speckle, and divergence adjustability. However, VCSELs suffer from reduced power density due to their spacing requirements.

Because, on the whole, VCSELs offer the best overall combination of advantages, a need exists for an optical apparatus that leverages the noted advantages of VCSELs while overcoming - or compensating for - their disadvantages, with the most notable disadvantage being the spacing requirements of the VCSELs within a VCSEL array.

SUMMARY

In general terms, each of various embodiments of a light combiner is optically coupled with an array of micro-emitters. In principle, the micro-emitters may take any of several forms of light-emitting element, but various versions of the light combiner are advantageously implemented in conjunction with arrays of vertical cavity side emitting lasers (hereinafter,“VCSEL arrays”).

Illustratively embodied, a light combiner assembly includes a fixed emitter array incorporating a plurality of micro-emitter elements - or“micro-emitters” - having a predetermined emitter-array order and spacing according to which the micro-emitters are mutually arranged and spaced. The emitter array further defines, or is further characterized by, an emitter-array density which is indicative of the quantity of micro-emitters per unit area within the emitter array. In addition to the light output of each micro-emitter, the arrangement and spacing of the micro-emitters further defines a micro-emitter light- output density (e.g., VCSEL-array light-output density).

A light combiner is defined by an optical fiber bundle having mutually opposed bundle first and second ends and including a plurality of adjacently arranged constituent optical fibers. Each constituent optical fiber has a light-input end coinciding with the bundle first end and a light-output end coinciding with the bundle second end. According to at least one version, the constituent optical fibers are mutually and adjacently fused for at least a portion of their lengths extending from the light-input ends at the bundle first end toward the light-output ends at the bundle second end. In any event, the light- input ends define a combiner input array at the bundle first end according to which the light-input ends are mutually arranged and spaced in a manner further defining an input-array density indicative of the quantity of light-input ends per unit area within the combiner input array.

Across alternative implementations, a main objective of the light combiner is to capture at the bundle first end (alternatively,“bundle input end”) the overall light energy output of the emitter array and transmit it through the optical fiber bundle for outputting - or“emission” -- through the bundle second end (alternatively, “bundle output end”). In furtherance of this objective, the mutual spacing and arrangement of the light-input ends of the combiner input array correspond to the mutual spacing and arrangement of the micro-emitters of the emitter array, and the bundle first end is optically aligned with the emitter array, such that the light-input end of each constituent optical fiber is optically aligned with a single micro-emitter in the emitter array for the selective collection of light outputted by that single micro-emitter. However, such an embodiment does not imply that there cannot be more than one constituent optical fiber optically aligned with a particular micro-emitter.

At the bundle second end, the light-output ends of the constituent optical fibers define a combiner output array according to which the light-output ends are mutually arranged and spaced in a manner further defining an output-array density indicative of the quantity of light-output ends per unit area within the combiner output array. In order to increase the light-output density of the emitter array, the constituent optical fibers of the optical fiber bundle collectively taper down in the direction extending from the bundle first end toward the bundle second end such that the output-array density according to which the light-output ends are mutually spaced is more dense than the input-array density according to which the light-input ends are mutually spaced.

Another factor important to embodiments of the present invention is maximizing the efficiency of the optical coupling between the emitter array and the input array defined by the light-input ends of the optical fibers at the bundle input end. More specifically in this regard, light-capture efficiency is a principal objective. Accordingly, relative numerical aperture is an important parameter factored into the fabrication of various embodiments, as illustratively described below.

Each micro-emitter has an associated micro-emitter numerical aperture corresponding to a cone angle over which that micro-emitter emits light. In association with embodiments in which the micro-emitters are VCSELs, the micro-emitter numerical aperture may be alternatively described and claimed as“VCSEL numerical aperture.” Additionally, each constituent optical fiber has an associated fiber numerical aperture corresponding to a cone angle over which the light-input end of that optical fiber collects light outputted by the micro-emitter with which that light-input end is optically aligned. The fiber numerical aperture of each optical fiber is configured to match as closely as practicable the microemitter numerical aperture of the micro-emitter element with which it is optically aligned in a manner configured to maximize efficiency in capturing within that optical fiber the light outputted by the optically aligned micro-emitter.

In a traditional fused optical fiber taper, for example, a fused bundle is heated and stretched which, while locally reducing the overall bundle diameter, also reduces the diameters of the individual constituent optical fibers within that region of reduced bundle diameter. By contrast, in each of various embodiments of the present invention, the optical fiber bundle defining the light combiner is configured such that, over the length that the constituent optical fibers collectively taper down to a denser array, the diameter of each optical fiber individually is configured to remain constant. This configuration may be achieved by alternative methods.

One method of enabling collective tapering involves forming a fused optical fiber bundle wherein the core of each constituent optical fiber has fusedly collapsed about it two cladding layers: an inner cladding and an outer cladding. The inner cladding immediately surrounding the core is a permanent optical cladding that facilitates internal reflection along the entire length of the fiber. The outer cladding, however, is selectively leachable (or etchable) when exposed to an outer-cladding solvent which, in alternative versions, may be an acid or a base, for example.

The optical fiber bundle is selectively dissolved along portion of its length extending from the bundle second end toward - but not all the way to - the bundle first end. In this way, the light-input ends of the constituent optical fibers are“fusedly retained” in their respective positions defining the combiner input array at the bundle first end. However, with the outer cladding selectively dissolved, the light-output ends are freed (unbound) from one another. The light-output ends of the constituent optical fibers are then adjacently packed to form the combiner output array according to which the light-output ends are mutually arranged and spaced in a manner further defining an output-array density more dense than the input-array density. It will be appreciated from the foregoing explanation that the diameter of each constituent optical fiber that is configured to remain constant is that diameter corresponding to the outer boundary of the inner cladding (the permanent optical cladding), exclusive of the soluble outer cladding. Selective etching - or leaching - of such fused bundles is known in the related arts with ubiquity sufficient to obviate the need for more detailed explanation or diagrammatic illustration of process specifics.

The light-output ends of the constituent optical fibers defining the combiner output array are retained in fixed mutual relationship. The mechanical retention of the light-output ends may be achieved by alternative means including, by way of non-limiting example, at least one of (i) an adhesive, such as epoxy, (ii) a mechanical band or sleeve, and (iii) heat fusing. In alternative versions, the light-output ends of the optical fibers are either (a) brought down into the“tighter” (more dense) combiner output array and arranged in the same relative positions as their corresponding light-input ends or (b) spatially randomized in order to facilitate uniformity in the light output.

An alternative embodiment includes the elements described above in substantially the same relative arrangement, but further includes a light-mixing element. More specifically, in order to facilitate a more homogenous and randomized (e.g., uniform) overall output of light, a light-mixing element is optically coupled with the bundle second end (the bundle output end) of the tapered light combiner previously described. Illustratively embodied, the light-mixing element comprises an optically- transmissive rod (alternatively, a“mixing rod”) through which light propagates by internal reflection between longitudinally opposed mixing-rod first and second ends.

As with most internally-reflecting light conduits, an embodied mixing rod would commonly include an optical core with a core refractive index and a rod cladding with a cladding refractive index lower in magnitude than the core refractive index. However, the mixing rod could be fabricated from a single optically-transmissive material with a core refractive index and rely on the surrounding environment (e.g. air or another gas or liquid) of lower refractive index to facilitate internal reflection.

Particular embodiments of the mixing rod can exhibit any of various cross-sectional geometries including, by way of non-limiting example, (i) round, (ii) square, (iii) rectangular, (iv) triangular, (v) pentagonal, or (vi) other regular or irregular polygonal shape. However, experimentation within the context of various implementations indicates an hexagonal cross-sectional geometry is particularly advantageous to the promotion of light mixing.

In a still-additional configuration, a mixing rod of a type previously described is holistically optically coupled with the emitter array rather than with the bundle second end (the smaller bundle output end) of the tapered light combiner. An illustrative such embodiment is presented in the detailed description with an associated drawing.

Illustratively embodied, the emitter array and light combiner and/or mixing rod are packaged at least partially within a housing including a base surface or“header” and a“can” or“cap,” as those terms are understood in the electronic and optoelectronic packaging arts. The header provides a substrate on which electronic components are mounted, and through which those components are powered through electrical leads passing through, or otherwise carried by, the header. In embodiments of the present invention, the electronic components mounted to the header would include the emitter array defined by the micro-emitters.

The cap may be a generally cylindrical structure defined by a cylindrical side wall and a cap end wall. When the cap is mounted to the header, the cap end wall is generally opposite the header and the emitter array. In optoelectronic packaging generally, this wall frequently includes a translucent window through which light emitted from an enclosed emitter or emitter array can pass and exit the can, or through which light can enter from the outside for detection by sensors contained within the housing. In various implementations of the present invention, however, it is not critical that this wall constitute or include a window. Instead, the cap end wall serves as a support structure through with the lighter combiner passes, and by which the light combiner is supported in the desired proximity and orientation relative to the emitter array defined on the header. More specifically, an opening is defined through the cap end wall through which the light combiner passes. The light combiner is sealed within the opening by any of various means including, by way of non-limiting example, at least one of (i) heat fusion, (ii) soldering, and (iii) adhesive, such as epoxy.

Representative embodiments are more completely described and depicted in the following detailed description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a micro-emitter array optically aligned with a light combiner comprising a partially fused optical fiber bundle;

FIG. 2 is a schematic longitudinal cross-sectional illustration of a light combiner comprising a partially fused optical fiber bundle incorporating collectively tapered optical fibers, wherein each of the optical fibers is of constant diameter over its own length;

FIG. 3 is a cross-sectional view of a single micro-emitter optically aligned with a single optical fiber;

FIG. 4 shows, in a longitudinal cross section, a light combiner like that of FIG. 2 optically coupled “in series” with a light-mixing element configured as a mixing rod;

FIG. 5 schematically depicts an illustrative environment in which an emitter array and light combiner are situated; and

FIG. 6 schematically depicts an illustrative environment in which an emitter array and light-mixing element are situated.

DETAILED DESCRIPTION

The following description of variously embodied emitter array and light combiner assemblies is demonstrative in nature and is not intended to limit the invention or its application of uses. Accordingly, the various implementations, aspects, versions and embodiments described in the summary and detailed description are in the nature of non-limiting examples falling within the scope of the appended claims and do not serve to restrict the maximum scope of the claims.

Schematically depicted in FIG. 1 is an exploded view of a light combiner 100 for increasing the light energy density of fixed emitter array 200 incorporating a plurality of micro-emitters 210. The micro-emitters 210 collectively exhibit a predetermined emitter-array order and spacing according to which the micro-emitters 210 are mutually arranged and spaced. The emitter array 200 is further characterized by an emitter-array density DEA which is indicative of the quantity of micro-emitters 210 per unit area within the emitter array 200. In addition to the light output of each micro-emitter 210, the arrangement and spacing of the micro-emitters 210 further defines a micro-emitter light-output density DMELO.

Referring still to FIG. 1 , and the longitudinal cross-sectional side view of FIG. 2, a light combiner 100 is defined by an optical fiber bundle 110. The optical fiber bundle 110 has mutually opposed bundle first and second ends 120 and 130 between which first and second ends 120 and 130 extends longitudinally along a bundle axis AB a plurality of adjacently arranged constituent optical fibers 150. Each constituent optical fiber 150 has a light-input end 152 coinciding with the bundle first end 120 and a light-output end 154 coinciding with the bundle second end 130.

According to at least one version, the constituent optical fibers 150 are mutually and adjacently fused for at least a portion of their lengths extending from the light-input ends 152 at the bundle first end 120 toward the light-output ends 154 at the bundle second end 130. The light-input ends 152 define a combiner input array 125 at the bundle first end 120 according to which the light-input ends 152 are mutually arranged and spaced in a manner further defining an input-array density Du indicative of the quantity of light-input ends 152 per unit area within the combiner input array 125.

As explained in the summary, an objective of various embodiments is to capture at the bundle first end 120 (a.k.a., the bundle input end 120) of the light combiner 100 the overall light energy emitted by the emitter array 200, and to conduct that light through the optical fiber bundle 110 for emission through the bundle second end 130. In each of various configurations, such as that depicted in FIGS. 1 , the mutual spacing and arrangement of the light-input ends 152 of the combiner input array 125 correspond to the mutual spacing and arrangement of the micro-emitters 210 of the emitter array 200. Moreover, the bundle first end 120 is optically aligned with the emitter array 200 such that the light-input end 152 of each constituent optical fiber 150 is optically aligned with a single corresponding micro-emitter 210 in the emitter array 200 for the selective collection of light outputted by that single micro-emitter 210.

The light-output ends 154 of the constituent optical fibers 150 define, at the second bundle end 130, a combiner output array 135 according to which the light-output ends 154 are mutually arranged and spaced in a manner further defining an output-array density DLO. In order to increase the light- output density of the emitter array 200, the constituent optical fibers 150 collectively taper down in the direction extending away from the bundle first end 120 toward the bundle second end 130. In this way, the output-array density DLO according to which the light-output ends 154 are mutually spaced is denser than the input-array density Du according to which the light-input ends 152 are mutually spaced.

Discussed briefly in the summary was the importance of the light-capture efficiency of the light combiner 100 relative to the light emitted by the emitter array 200. Illustrative parameters with particular regard to numerical aperture are described with reference to the side view schematic of FIG. 3.

Shown in FIG. 3 is a selected section of the emitter array 200 with a single micro-emitter 210 optically aligned with the light-input end 152 of a single constituent optical fiber 150. Although the schematic includes only a single instance of each of the aforesaid elements, for purposes of clarity in depiction and explanation, it is to be understood that the illustrative parameters apply over a large plurality of micro-emitters 210 and corresponding constituent optical fibers 110 in actual practice. The micro-emitter 210 has an associated micro-emitter numerical aperture NAME corresponding to a“cone angle” over which that micro-emitter 210 emits light. The corresponding constituent optical fiber 150 with which the micro-emitter 210 is optically aligned has an associated fiber numerical aperture NAF corresponding to a cone angle (e.g., a“light-acceptance angle”) over which the light-input end 152 of the optical fiber 150 collects light outputted by the micro-emitter 210. The fiber numerical aperture NAF of the optical fiber 150 is configured to match as closely as practicable the micro-emitter numerical aperture NAME of the micro-emitter 210 with which it is optically aligned. The objective is to maximize the efficiency in capturing within the optical fiber 150 the light outputted by the micro-emitter 210.

While“matching” of the micro-emitter numerical aperture NAME and the fiber numerical aperture NAF may - in the absence of further explanation - imply that these numerical apertures NAME and NAF should be equal, this need not strictly be the case. For instance, if the fiber numerical aperture NAF defines a light-acceptance angle that is larger than the light-emission angle defined by the micro-emitter numerical aperture NAME and, furthermore, the micro-emitter 210 and light-input end 152 are in sufficiently close proximity, then all of the light outputted by the micro-emitter 210 would, in theory, be captured for propagation through the constituent optical fiber 150. If, however, the micro-emitter numerical aperture NAME were very much larger than the fiber numerical aperture NAF, then a considerable percentage of the light emitted by the micro-emitter 210 would go uncaptured by the corresponding constituent optical fiber 150, unless the micro-emitter 210 and light-input end 152 were in very close - perhaps undesirably close - proximity. Based on the preceding,“match as closely as practicable” relative to the numerical apertures NAME and NAF should be interpreted broadly in light of the desired objective of maximum light-capture efficiency, and not strictly in numerical terms unless explicit claim language to the contrary requires a strictly numerical interpretation of same.

According to at least one embodiment, the optical fiber bundle 110 defining the light combiner 100 is configured such that, over the length that the constituent optical fibers 150 collectively taper down to a denser array, the fiber diameter DF of each optical fiber 150 individually is constant. A resultant product produced by one method of collective tapering - while maintaining constant the fiber diameter DF of each optical fiber 150 -- is shown in schematic cross section in FIG. 2 previously introduced. As described in the summary, the illustrative method involves forming a fused optical fiber bundle 110 wherein the core 156 of each constituent optical fiber 150 has collapsed about it two cladding layers: an inner cladding 157 and an outer cladding 158. The inner cladding 157 immediately surrounding the core 156 is a permanent optical cladding 157 that facilitates internal reflection along the length of the optical fiber 150. The outer cladding 158, however, is selectively etched by exposure to an outer-cladding solvent (not shown).

With continued reference to FIG. 2, it can be seen that the outer claddings 158 within optical fiber bundle 110 have been selectively dissolved along a lengthwise portion extending from the bundle second end 130 toward - but not all the way to - the bundle first end 120. Consequently, the light-input ends 152 of the constituent optical fibers 150 are“fusedly retained” in their respective positions defining the combiner input array 125 at the bundle first end 120. Flowever, with the outer cladding 158 selectively dissolved, the light-output ends 152 are, during an intermediate step not shown, freed (unbound) from one another. Subsequently, the light-output ends 154 of the constituent optical fibers 150 were then adjacently packed to form the combiner output array 135 according to which the light- output ends 154 are mutually arranged and spaced in a manner further defining the output-array density DLO more dense than the input-array density Du. It can furthermore be appreciated from FIG. 2 that the fiber diameter DF of each constituent optical fiber 150 that remains constant is that diameter corresponding to the outer boundary defined by the inner cladding 157 (the permanent optical cladding 157), exclusive of the soluble outer cladding 158.

With reference to the cross-sectional representation of FIG. 4, an alternative embodiment further including a light-mixing element 300 is now described. The illustrative configuration of FIG. 4 includes the light combiner 100 of FIG. 2 optically coupled“in series” with the light-mixing element 300. The light-mixing element 300 is an optical ly-transmissive mixing rod 310 through which light propagates by internal reflection between longitudinally opposed mixing-rod first and second ends 320 and 330. Extending along a mixing rod axis AMR -- which is coextensive with the bundle axis AB - between the mixing-rod first and second ends 320 and 330 is an optical mixing-rod core 350 and a mixing-rod cladding 360 disposed about the mixing-rod core 350. The mixing-rod core 350 and cladding 360 have, respectively, a core refractive index and a cladding refractive index selected to facilitate light propagation through the mixing rod 310 by internal reflection.

An objective of the mixing rod 310 is to facilitate a more homogenous and randomized (uniform) overall output of light emitted from the emitter array 200 and through the light combiner 100. Accordingly, the light-mixing element 300 (mixing rod 310) is optically coupled with the bundle second end 130 of the tapered light combiner 100. Configured thusly, light emitted from the micro-emitters 210 of the emitter array 200 (not shown in FIG. 4) is inputted into, and transmitted through, the optical fibers 150 of the optical fiber bundle 110 constituting the light combiner 100. The light exiting the bundle second end 130 is then inputted into the mixing-rod first end 320. Within the mixing rod 310, the light received from the constituent optical fibers 150 of the light combiner 100 is internally reflected, mixed, randomized, and homogenized before exiting the mixing-rod second end 330.

As discussed in the summary, the mixing rod 310 can exhibit any of various cross-sectional geometries. Flowever, experimentation within the context of various implementations indicates that a hexagonal cross-sectional geometry is particularly advantageous for facilitating light mixing. An hexagonal cross-section is illustrated by that portion of FIG. 4 indicating a cross-section of the mixing rod 310 as viewed into a transverse rod cross-sectional plane PTCS oriented orthogonally to the mixing rod axis AMR.

Referring now to FIG. 5, schematically depicted is an illustrative environmental setting in which the light combiner 100 and emitter array 200 are packaged and implemented. As embodied in FIG. 5, the emitter array 200 and light combiner 100 are packaged within a housing 400 including a base surface or“header 410” and a“can” or“cap 420.” The header 410 provides a substrate on which electronic and optoelectronic components are mounted, and through which those components are powered through electrical leads 412 passing through, or otherwise carried by, the header 410. In the specific context of FIG. 5, the optoelectronic components carried by the header 410 include the micro- emitters 210 defining the emitter array 200.

The cap 420 may be a generally cylindrical structure defined by a cylindrical side wall 422 and a cap end wall 426. When the cap 420 is mounted to the header 410, the cap end wall 426 is generally opposite the header 410. In optoelectronic packaging generally, this cap end wall 426 frequently includes a translucent window 428 through which light -- represented throughout by arrows -- emitted from an enclosed emitter array 200 can pass and exit the cap 420, or through which light can enter from the outside for detection by internal sensors (not shown) contained within the housing 400. In various implementations of the present invention, however, it is not critical that this cap end wall 426 include a window 428. Instead, the cap end wall 426 serves as a support structure through with the light combiner 100 passes and is supported in the desired proximity and orientation relative to the emitter array 200. More specifically, an end-wall opening 429 is defined through the cap end wall 426 (a window 428 thereof in the particular case of FIG. 5). The light combiner 100 is sealed within the end- wall opening 429 by any of various means including, by way of non-limiting example, at least one of (i) heat fusion, (ii) soldering, and (iii) adhesive, such as epoxy. In a case in which the cap end wall 426 is formed of glass, for example, glass frit may be used to heat fuse and seal the light combiner 100 within the cap end wall 426.

Referring still to FIG. 5, in various optoelectronic implementations, light that exits the light combiner 100 through the cap end wall 426 may be transmitted to backend optics 500 for further manipulation. In the illustrative version of FIG. 5, various optical components 510 in the form or lenses 520, 522, and 524 are provided for the purpose of contextual environment. Accordingly, it is to be understood that, unless otherwise specified or claimed, the backend optics 500 could take any of various forms including, by way of non-limiting example, one or more of (i) a defractive element, (ii) a refractive element, (iii) a filtering element, (iv) a polarizing element, (v) a shutter, (vi) a baffle, (vii) a detector, (viii) an optical fiber, and (ix) an optical fiber bundle.

Referring now to FIG. 6, an alternative implementation is shown. In FIG. 6, all illustrative elements are the same as those of FIG. 5 with the exception that a light-mixing element 300 (mixing rod 310) has substituted for the light combiner 100 (optical fiber bundle 110). Accordingly, like reference characters denote the same or analogous elements in FIG. 6 as they do in FIG. 5, irrespective of the fact that the descriptions of same are not repeated with direct reference to FIG. 6. The mixing rod 310 is positioned within the cap 420 such that it is directly and holistically optically coupled with the emitter array 200 rather than with the bundle second end 130 (the smaller bundle output end) of the tapered light combiner 100.

In an embodiment like that of FIG. 6, greater emphasis is placed on mixing and homogenizing the light output of individual micro-emitters 210 forming the emitter array 200. However, while the mixing rod 310 itself in this case does not increase the density of the light energy outputted by the emitter array 200, it does“preserve” that light density until the emitted light is in closer proximity to the backend optics 500.

The foregoing is considered to be illustrative of the principles of the invention. Furthermore, since modifications and changes to various aspects and implementations will occur to those skilled in the art without departing from the scope and spirit of the invention, it is to be understood that the foregoing does not limit the invention as expressed in the appended claims to the exact constructions, implementations and versions shown and described.

Claims

What is claimed is:

1. An emitter array and light combiner assembly for increasing the light-output

density of the emitter array, the assembly comprising:

a fixed emitter array of micro-emitters having a predetermined array order and spacing according to which the micro-emitters are mutually arranged and spaced, and which further defines an array light-output density;

a light combiner defined by an optical fiber bundle having opposed bundle first and second ends and including a plurality of adjacently arranged constituent optical fibers, each optical fiber having a light-input end coinciding with the bundle first end and a light-output end coinciding with the bundle second end, wherein

(i) the constituent optical fibers are adjacently fused for at least a portion of their lengths extending from the light-input ends at the bundle first end toward the light- output ends at the bundle second end;

(ii) the light-input ends define a combiner input array at the bundle first end according to which the light-input ends are mutually arranged and spaced in a manner further defining an input-array density;

(iii) the mutual spacing and arrangement of the light-input ends of the light- input array correspond to the mutual spacing and arrangement of the micro-emitters of the emitter array, and the bundle first end is optically aligned with the emitter array, such that the light-input end of each constituent optical fiber is optically aligned with a single micro-emitter in the micro-emitter array for the selective collection of light outputted by that single micro-emitter;

(iv) the light-output ends define a combiner output array at the bundle second end according to which the light-output ends are mutually arranged and spaced in a manner further defining an output-array density; and

(v) the constituent optical fibers of the optical fiber bundle collectively taper down in the direction from the bundle first end toward the bundle second end such that, the output-array density according to which the light-output ends are mutually spaced is more dense than the input-array density according to which the light-input ends are mutually spaced, thereby resulting in an increase in light-output density of the microemitter array.

2. The assembly of claim 1 wherein

(i) each micro-emitter has an associated micro-emitter numerical aperture corresponding to a cone angle over which that micro-emitter emits light;

(ii) each constituent optical fiber has an associated fiber numerical aperture corresponding to a cone angle over which the light-input end of that optical fiber collects light outputted by the micro-emitter with which it is optically aligned; and

(iii) the fiber numerical aperture of each optical fiber is configured to match as closely as practicable the micro-emitter numerical aperture of the micro-emitter with which it is optically aligned in a manner configured to maximize the efficiency in capturing within each optical fiber the light outputted by the micro-emitter with which that optical fiber is optically aligned.

3. The assembly of claim 2 wherein, within the optical fiber bundle over the

length of which the constituent optical fibers collectively taper down to a more dense array, the diameter of each optical fiber individually is configured to remain constant.

4. The assembly of claim 1 wherein, within the optical fiber bundle over the

5. The assembly of claim 1 further comprising a light-mixing element

configured as a mixing rod through which light propagates by internal reflection between longitudinally opposed mixing-rod first and second ends, the mixing rod being optically coupled with the bundle second end of the light combiner such that (i) light exiting the bundle second end is inputted into the mixing-rod first end and (ii) within the mixing rod, the light received from the constituent optical fibers of the light combiner is internally reflected, mixed, randomized, and homogenized before exiting the mixing-rod second end.

6. The assembly of claim 5 wherein

7. The assembly of claim 6 wherein, within the optical fiber bundle over the

8. The assembly of claim 5 wherein, within the optical fiber bundle over the

9. The assembly of claim 1 packaged at least partially within a housing

comprising a header and a cap mounted to the header, wherein

(i) the emitter array is mounted to the header;

(ii) the cap includes at least one side wall and cap end wall including an opening defined therethrough, and is mounted to the header such that the cap end wall is opposite the header and the emitter array;

(iii) the light combiner passes through the opening in the cap end wall and being sealed within the opening such that the cap end wall serves as a support structure retains the light combiner in a desired proximity and orientation relative to the emitter array defined on the header.

10. A VCSEL array and light combiner assembly for increasing the light-output

density of the VCSEL array, the assembly comprising:

a fixed array of VCSEL elements having a predetermined VCSEL-array order and spacing according to which the VCSEL elements are mutually arranged and spaced, and which further defines a VCSEL-array light-output density;

(iii) the mutual spacing and arrangement of the light-input ends of the light- input array correspond to the mutual spacing and arrangement of the VCSEL elements of the VCSEL array, and the bundle first end is optically aligned with the VCSEL array, such that the light-input end of each constituent optical fiber is optically aligned with a single VCSEL element in the VCSEL array for the selective collection of light outputted by the single VCSEL element;

(v) the constituent optical fibers of the optical fiber bundle collectively taper down in the direction from the bundle first end toward the bundle second end such that, the output-array density according to which the light-output ends are mutually spaced is more dense than the input-array density according to which the light-input ends are mutually spaced, thereby resulting in an increase in light-output density of the VCSEL array.

1 1. The VCSEL array and light combiner assembly of claim 1 0 wherein

(i) each VCSEL element has an associated VCSEL numerical aperture corresponding to a cone angle over which that VCSEL element emits light;

(ii) each constituent optical fiber has an associated fiber numerical aperture corresponding to a cone angle over which the light-input end of that optical fiber collects light outputted by the VCSEL element with which it is optically aligned; and

(iii) the fiber numerical aperture of each optical fiber is configured to match as closely as practicable the VCSEL numerical aperture of the VCSEL element with which it is optically aligned in a manner configured to maximize the efficiency in capturing within each optical fiber the light outputted by the VCSEL element with which that optical fiber is optically aligned.

12. The VCSEL array and light combiner assembly of claim 1 1 wherein, within the optical fiber bundle over the length of which the constituent optical fibers collectively taper down to a more dense array, the diameter of each optical fiber individually is configured to remain constant.

13. The VCSEL array and light combiner assembly of claim 10 wherein, within the

optical fiber bundle over the length of which the constituent optical fibers collectively taper down to a more dense array, the diameter of each optical fiber individually is configured to remain constant.

14. A light combiner comprising:

an optical fiber bundle having opposed bundle first and second ends and including a plurality of adjacently arranged constituent optical fibers, each optical fiber having a light-input end coinciding with the bundle first end and a light-output end coinciding with the bundle second end, wherein

(i) the constituent optical fibers are adjacently fused for at least a portion of their lengths extending from the light-input ends at the bundle first end toward the light-output ends at the bundle second end;

(iii) the light-output ends define a combiner output array at the bundle second end according to which the light-output ends are mutually arranged and spaced in a manner further defining an output-array density;

(iv) the constituent optical fibers of the optical fiber bundle collectively taper down in the direction from the bundle first end toward the bundle second end such that, the output- array density according to which the light-output ends are mutually spaced is more dense than the input-array density according to which the light-input ends are mutually spaced; and

(v) within the optical fiber bundle over the length of which the constituent optical fibers collectively taper down to a more dense array, the diameter of each optical fiber individually is configured to remain constant.