WO2023156630A1

WO2023156630A1 - Infrared-reflective nanostructures

Info

Publication number: WO2023156630A1
Application number: PCT/EP2023/054102
Authority: WO
Inventors: Ragip Pala
Original assignee: Meta Materials Inc.
Priority date: 2022-02-18
Filing date: 2023-02-17
Publication date: 2023-08-24

Abstract

Infrared reflectors and methods for making infrared reflectors are disclosed.

Description

INFRARED-REFLECTIVE NANOSTRUCTURES

FIELD OF THE INVENTION

[0001] The present invention is in the field of metamaterials. More particularly, the invention relates to optical filters based on metamaterials.

BACKGROUND

[0002] Development of reflective coatings against laser strikes in the IR spectrum became more challenging with the availability of high-powered laser weapons. Absorption of laser energy at defect sites, or higher than target intrinsic absorption in the coating material, can cause thermal damage to the system.

[0003] Resonant reflective surfaces, such as photonic crystals or guided mode resonance structures, are an alternative to conventional multi-layer reflective coatings. By tuning the resonant reflectivity to cover the incident wavelength, an ultrathin film of nanostructured surface can provide high reflectance with preferred absorptivity values. However, one challenge is such resonant structures have strong wavelength and angular dependence. Another challenge is manufacturing such structures at scale. For example, undesired fabrication imperfections, e.g., non-uniformities and deviations from the ideal design along the sample surface, will induce variations from the expected optical response.

[0004] Thus, what is needed are improved, scalable, reflective materials and coatings that maintain minimal absorptivity of laser energy.

SUMMARY

[0005] It has been discovered that nanopattem arrays that have high reflectance and low absorbance for wavelength bands in the infrared can be produced at scale using lithographic pattern transfer techniques. This discovery has been exploited to provide the present disclosure, which is directed to a high-impedance metasurface material for IR reflection compatible with the scalable rolling mask lithography (RML) and nanoimprint lithography techniques.

[0006] In general, in one aspect, the disclosure provides an infrared reflector comprising a layer comprising a dielectric material patterned to provide an array of nanostructures, the nanostructures being pillars or holes and having a dimension normal to the layer (height or depth as the case may be) in a range from about 200 nm to about 5,000 nm, the nanostructures having a lateral dimension in a range from about 100 nm to about 1,000 nm and a periodicity in at least one lateral direction in a range from about 300 nm to about 2,000 nm. The layer has a reflectivity of about 90% or more for normally incident radiation in a band of wavelengths in a range from about 700 nm to about 12,000 nm and absorbs about 5% or less of the normally incident radiation in the band of wavelengths.

[0007] In some examples, the pillars are formed from the dielectric material. In certain examples, the holes are formed in a continuous layer of the dielectric material.

[0008] In some examples, the dielectric material is an amorphous dielectric material.

[0009] In some examples, the dielectric material is silicon (e.g., but not limited to, crystalline silicon, polycrystalline silicone, amorphous silicon).

[0010] In some examples, the nanostructures are cylindrical nanostructures.

[0011] In some examples, the array has the same periodicity in two different directions in the plane.

[0012] In some examples, the reflectivity is about 95% or more (e.g., but not limited to, about 97% or more, about 98% or more, about 99% or more). In certain examples, the reflectivity is about 90% or more (e.g., but not limited to, about 95% or more, about 98% or more, about 99% or more) for non-normally incident radiation in the band of wavelengths.

[0013] In some examples, the absorption is about 2% or less (e.g., but not limited to) about 1% or less, about 0.1% or less) for at least some normally incident radiation in the band of wavelengths. In certain examples, the absorption is about 5% or less (e.g., but not limited to) about 2% or less, about 1% or less, about 0.1% or less) for at least some non-normally incident radiation in the band of wavelengths.

[0014] In some examples, the dielectric material has a refractive index of about 1.5 or more (e g., but not limited to, about 1.6 or more, about 1.7 or more, about 1.8 or more, about 1.9 or more, about 2.0 or more, about 2.5 or more, about 3.0 or more).

[0015] In some examples, the layer has a thickness of about 500 nm or more (e.g., but not limited to, about 800 nm or more, about 1,000 nm or more, about 1,200 nm or more, 1,500 nm or more, about 2,000 nm or more, about 4,000 nm or less, about 3,000 nm or less). [0016] In some examples, the band of wavelengths is in a range from about 800 nm to about 2,000 nm (e.g., but not limited to, about 800 nm to about 1,700 nm, about 1,000 nm to about 1,500 nm, about 1,100 nm to about 1,300 nm).

[0017] In some examples, the band of wavelengths has a bandwidth in a range from about 10 nm to about 500 nm (e.g., but not limited to, about 20 nm or more, about 50 nm or more, about 100 nm or more, about 300 nm or less, about 200 nm or less, about 150 nm or less).

[0018] In some examples, the layer extends over an area of about 100 cm² or more (e.g., but not limited to, about 500 cm² or more, about 1,000 cm² or more, about 5,000 cm² or more about 10,000 cm² or more, about 100,000 cm² or more).

[0019] In certain examples, the article comprises a substrate supporting the layer. The substrate can be a flexible substrate or a rigid substrate. The substrate can comprise the dielectric material. In some examples, the substrate is a plastic substrate or a glass substrate. [0020] In general, in another aspect, the disclosure features a method of manufacturing an infrared reflector, including forming a layer on a substrate, the layer comprising a dielectric material patterned to provide an array of nanostructures, the nanostructures being pillars or holes and having a dimension normal to the layer (height/depth) in a range from about 200 nm to about 5,000 nm, the nanostructures having a lateral dimension in a range from about 100 nm to about 1,000 nm and a periodicity in at least one lateral direction in a range from about 300 nm to about 2,000 nm. The layer has a reflectivity of about 90% or more for normally incident radiation in a band of wavelengths in a range from about 700 nm to about 12,000 nm and absorbs about 5% or less of the normally incident radiation in the band of wavelengths. In some examples, the layer is formed using nano-imprint lithography. In other examples, the layer is formed using rolling mask lithography.

DESCRIPTION OF THE DRAWINGS

[0021] The foregoing and other objects of the present disclosure, the various features thereof, as well as the disclosure itself may be more fully understood from the following description, when read together with the accompanying drawings in which:

[0022] FIG. 1A is a photographic representation of a scanning electron microscopy image of a negative resist layer for nanostructures made using the technology disclosed herein in accordance with many examples; [0023] FIG. IB is a photographic representation of a scanning electron microscopy image of a positive resist layer nanostructures made using the technology disclosed herein in accordance with many examples;

[0024] FIG. 1C is a photographic representation of a scanning electron microscopy image of nanostructures made using the technology disclosed herein in accordance with many examples;

[0025] FIG. ID is a photographic representation of a large area substrate with patterned modular areas in accordance with many examples;

[0026] FIG. IE is a photographic representation of a large area substrate, patterned with a continuous array of nanostructures with different sizes in accordance with many examples; [0027] FIG. IF is a photographic representation of a flexible substrate with continuous nanopatterned array in accordance with many examples;

[0028] FIG. 2A is a photographic representation of a flexible substrate with a nanopattemed array in accordance with many examples;

[0029] FIG. 2B is a graphic representation of an atomic force microscopy images of nanostructures made using the technology disclosed herein in accordance with many examples; [0030] FIG. 2C is a chart comparing the height and width of nanostructures made using the technology disclosed herein in accordance with many examples;

[0031] FIG. 2D is a scanning electron microscopy image of nanostructures made using the technology disclosed herein in accordance with many examples;

[0032] FIG. 3A is a simulated schematic representation of a hexagonal pillar array in side view in accordance with many examples;

[0033] FIG. 3B is a simulated schematic representation of a hexagonal pillar array in plan view in accordance with many examples;

[0034] FIGS. 3C is a graphical representation of a simulated heat map representative of the electric modes excited by normal incident light against a hexagonal pillar array, in accordance with many examples;

[0035] FIG. 3D is a graphical representation of a simulated heat map representative of the magnetic modes excited by normal incident light against a hexagonal pillar array, in accordance with many examples;

[0036] FIG. 3E is a graphical representation of a simulated heat map representative of the electric excited by normal incident light against a single resonator in accordance with many examples;

[0037] FIG. 3F is a graphical representation of a simulated heat map representative of the magnetic modes excited by normal incident light against a single resonator in accordance with many examples; [0038] FIG. 4A is a graphical representation of a simulated heat map comparing the reflectance of a hexagonal pillar array against pillar radius and wavelength in accordance with many examples;

[0039] FIG. 4B is a graphical representation of a chart comparing reflectivity of a hexagonal pillar array against wavelength in accordance with many examples;

[0040] FIG. 5A is a schematic representation of a rolling mask lithography (RML) system in accordance with many examples; and

[0041] FIG. 5B is a schematic representation of a portion of the RML system shown in FIG. 5A in accordance with many examples.

[0042] In the figures, like references indicate like elements.

DESCRIPTION

[0043] The disclosures of these patents, patent applications, and publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art as known to those skilled therein as of the date of the invention described and claimed herein. The instant disclosure will govern in the instance that there is any inconsistency between the patents, patent applications, and publications and this disclosure.

[0044] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The initial definition provided for a group or term herein applies to that group or term throughout the present specification individually or as part of another group, unless otherwise indicated.

[0045] As used herein, the articles “a” and “an” refer to one or to more than one (i.e., to at least one) of the grammatical object of the article By way of example, “an element” means one element or more than one element. Furthermore, use of the term “including” as well as other forms, such as “include,” “includes,” and “included,” is not limiting.

[0046] As used herein, the term “about” will be understood by persons of ordinary skill in the art and will vary to some extent on the context in which it is used. As used herein when referring to a measurable value such as an amount, a temporal duration, and the like, the term “about” is meant to encompass variations of ±20% or ±10%, including ±5%, ±1%, and ±0.1% from the specified value, as such variations are appropriate to perform the disclosed methods. [0047] The present disclosure provides a high-impedance metasurface material for effective IR reflection with wide-band operation (e.g., but not limited to, 1.1 pm - 1.3 pm - other examples being bands including 1064 nm, 980 nm or 1550 nm, for example 0.9 pm to 1.1 pm, 1.0 pm to 1,1 pm 1.4 pm to 1.6 pm or 1.5 pm to 1.7 pm, or more generally any 0.2 pm band, 0.3 pm band, 0.4 pm band, 0.5 pm band or 0.6 pm band within 0.9 pm to 1.6 pm, for example a band with a bandwidth in the range of 0.2 pm to 0.4 pm, 0.2 pm to 0.6 pm or 0.4 pm to 0.6 pm bandwidth and within the range of wavelengths of 0.9 pm to 1.6 pm ), compatible with a scalable lithography technique, for example nanoimprint or rolling mask lithography (RML) technique. RML and/or nanoimprint lithography (NIL) technology are utilized to fabricate IR-reflective nanopattemed material, e.g., but not limited to, patterned nanostructures on a substrate, in a scalable fashion. FIGS. 1A-1F and FIGS. 2A-2D show some examples of nanopatterned materials having similar dimensions fabricated using RML and NIL lithography tools. Optical designs for a pillar array or hole array suitable for fabrication using RML and/or NIL can be established empirically or using computer simulations, such as electromagnetic full-field simulations.

[0048] Disclosed herein are high-impedance metasurface designs for effective IR reflection compatible with a scalable RML or roll-to-roll (R2R) NIL techniques. Described further below are electromagnetic full field simulations of a material system, e.g., but not limited to, Si pillar array, producing an optical design within the fabrication capability of RML or NIL technology. [0049] Materials and corresponding optical structures are identified which enable a high reflectivity and low absorptivity compatible with a scalable fabrication technique. Fabrication imperfections, e.g., but not limited to, non-uniformities and deviations from the design along the substrate surface, which can induce variations from the expected optical response, may be within a margin for successful reflectance and absorbance within specified performance levels.

[0050] The present disclosure addresses such an exemplary material system composed of high index Si, patterned into a pillar array or a hole array. In some examples, the material system has a refractive index of about 1.5 or more (e.g., but not limited to, about 1.6 or more, about 1.7 or more, about 1.8 or more, about 1.9 or more, about 2.0 or more, about 2.5 or more, about 3.0 or more). The structure, including the material and dimensions of the nanopatterned layer, form a broadband metasurface reflector. For example, the structure reflects normally incident radiation in a band of wavelengths from about 800 nm to about 2,000 nm (e.g., but not limited to, about 800 nm to about 1,700 nm, about 1,000 nm to about 1,500 nm, about 1,100 nm to about 1,300 nm). In some examples, the band of wavelengths has a bandwidth in a range from about 10 nm to about 500 nm (e g., but not limited to, about 20 nm or more, about 50 nm or more, about 100 nm or more, about 300 nm or less, about 200 nm or less, about 150 nm or less). [0051] Scanning electron microscopy (SEM) photographs of exemplary resist layers and patterned nanostructures made using RML technology are shown in FIGS. 1A-1C. In each case, the (resulting) patterned nanostructures form a metasurface having high reflectivity (e.g., but not limited to, about 90% or more, about 95% or more, about 98% or more, about 99% or more) and low absorptivity (e g., but not limited to, about 2% or less, about 1% or less, about 0.1% or less) across a band of wavelengths. In some examples, the absorption is about 5% or less (e.g., but not limited to, about 2% or less, about 1% or less, about 0.1% or less) for at least some non-normally incident radiation in the band of wavelengths.

[0052] The patterned nanostructures extend in a plane (e.g., along two orthogonal directions). The nanostructures are formed in a layer of a dielectric material, such as an amorphous dielectric material. In some examples, the dielectric material is silicon (e.g., crystalline silicon, polycrystalline silicone, amorphous silicon). Other materials with similar dielectric properties can also be used including, but not limited to, GeSe, GaAs, etc. The dielectric material can be fused silica.

[0053] In a first example, the patterned nanostructures include an array of cylindrical holes. A SEM photograph of an exemplary array 108 of holes formed in a negative resist layer on a substrate 100, for example fused silica, formed using interference lithography with RML is shown in FIG. The patterned nanostructures / array of holes can be formed by etching the substrate and removing the negative resist layer. 1 A, with a scale bar of 1 micrometer shown inset. The array 108 is composed of individual holes 102 in a hexagonal pattern in a continuous layer of negative resist layer 110, the array 108 having a pitch 112 of about 1 micrometer. Each hole 102 has a depth 114 of about 800 nm and a width 106 of about 300 nm. Generally, holes 102 can have other dimensions. In some examples, the width 106 is in a range from about 50 nm to about 1,000 nm. In some examples, the height 114 is in a range from about 50 nm to about 3,000 nm (e.g., but not limited to, about 100 nm or more, about 200 nm or more, about 300 nm or more, about 400 nm or more, about 500 nm or more, about 800 nm or more, about 1,000 nm or more, about 1,200 nm or more, 1,500 nm or more, about 2,000 nm or more, such as about 4,000 nm or less, about 3,000 nm or less, about 2,000 nm or less, about 1,500 nm or less).

[0054] Another example an infrared reflector is composed of an array 116 of pillars. An array 116 of pillars 124 is formed in a positive resist layer on a substrate 118, for example fused silica, as shown in an SEM photograph in FIG. IB. The array may be formed using interference lithography with RML. Each pillar 124 of the array 116 in the positive resist layer has a height 120 of about 500 nm and a width 122 of about 300 nm. The patterned nanostructures / arrays of pillars can be formed by etching the substrate 118 and removing the positive resist layer. [0055] The infrared reflector resulting from etching and removing the positive resist layer from the structure shown in Figure IB, composed of an array 126 of cylindrical pillars, is shown in an SEM photograph in FIG. 1C. The array 126 was formed by etching the layer of fused silica in the substrate 118, providing pillars formed from the fused silica substrate 128 that remains after etching the substrate 118 in the areas exposed by the array 116. Each pillar 136 has a height 130 of about 1.5 pm and a width of about 500 nm. The array 126 is a hexagonal array with a pitch 134 of about 1.2 pm.

[0056] Substrate 128 is a fused silica substrate but, more generally, other substrate materials can be used. Generally, rigid or flexible substrate materials can be used. Examples of rigid substrate materials include inorganic glasses, such as silicate glasses including quartz glass. Materials suitable for flexible substrates include certain organic polymers such as a polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polyimide, polycarbonate, or cyclic olefin polymers. The substrate can be transparent at visible wavelengths (e.g., 400 nm to 700 nm). Alternatively or additionally, the substrate can be transparent at wavelengths in the infrared, including the operative wavelengths at which the array is reflective.

[0057] In some nonlimiting examples, the array of nanostructures can extend over a large area, such as over an area of about 100 cm² or more (e g., but not limited to, about 500 cm² or more, about 1,000 cm² or more, about 5,000 cm² or more about 10,000 cm² or more, about 100,000 cm² or more). For example, the nanostructure arrays can be formed using scalable processes such as RML and R2R NIL, which enable forming large format samples of the infrared reflectors. An example of a large area nanopattemed IR reflector 150 made using the RML is shown in a photograph in FIG. ID. The IR reflector 150 is composed of a glass substrate having dimensions of 0.3 m by 1 m. The nanopattern is formed in modular areas across the substrate. In this example, the nanostructures are pillars formed by etching a glass substrate.

[0058] Another example of an infrared reflector 160 is shown in a photograph in FIG. IE. The infrared reflector 160 is composed of a continuous array of etched pillars with different diameters on a glass (fused silica) substrate.

[0059] A further example of an infrared reflector 170 is shown in a photograph in FIG. IF. The infrared reflector 170 is composed of a continuous nanopattem array of SiO2 pillars on a polyethylene terephthalate (PET) substrate using a lift-off process.

[0060] In each of the prior examples, the nanopattem arrays are formed using RML. An example of an infrared reflector 200 composed of a nanopattern array formed using Nanoimprint Lithography is shown in a photograph in FIG. 2A. An atomic force microscopy micrograph of a portion of the array is shown in FIG. 2B. A plotted profile through a section of the micrograph is shown in FIG. 2C. The x-axis in this plot corresponds to the location through a section of the AFM profile shown in FIG. 2B, while the z-axis shows the height of the pillars (in nm). An SEM image of a portion of the array in plan view is shown in FIG. 2D. Infrared reflector 200 is composed of a 100 mm by 100 mm array of nanoimprinted pillars (cylinders) formed on a PET substrate. The array, in this example, is a square array. The pillars have a width of about 190 nm (see, FIG. 2D) and a height of about 150 nm (see, FIG. 1C). The pitch of the nanopattem array varies. The portion shown in FIG. 2B and 2C has a pitch of about 300 nm and the portion shown in FIG. 2D has a pitch of about 400 nm.

[0061] The interaction of electromagnetic radiation with nanostructures and arrays of nanostructures can be modeled using full field computer simulations. An exemplary simulation is discussed with reference to FIGS. 3A-3F. The simulation was performed for a hexagonal array 300 of pillars formed from Si, which is shown schematically in FIGS. 3A (side view) and 3B (plan view). The pillars have a radius of 200 nm (width 400 nm), a height of 300 nm, and a pitch of 650 nm. A plane wave 310 normally incident on the array was simulated.

[0062] The pillar array 300 forms a broadband metasurface reflector at about 1.2 pm wavelength. Simulated heat maps are shown in FIG. 3C and FIG. 3D representative of the electric and magnetic modes, respectively, excited by the plane wave 310 incident on the pillar array 300. The normally incident plane wave 310 excites electric (FIG. 3C) and magnetic modes (FIG. 3D) centered at 1.17 pm and 1.27 pm in the field surrounding the pillar array 300, respectively.

[0063] Simulated heat maps are shown in FIG. 3E and FIG. 3F representative of the electric and magnetic modes, respectively, excited by the incident plane wave 310 against an exemplary single pillar 320 of the pillar array 300 (Mie modes). The normally incident plane wave 310 excites electric (FIG. 3E) and magnetic Mie modes (FIG. 3F) centered at 1.17 pm and 1.27 pm in the field surrounding the single pillar 320, respectively. Bringing the simulated pillars of the array 300 closer (e.g., reducing the pitch) broadens the response of electric and magnetic Mie modes and further increases the reflectance. It is believed that the localized Mie modes induced in each pillar provides a relatively angle independent behavior as compared to photonic crystals or guided mode resonance type structure, for example. In the present example, two Mie modes are combined, which are close enough in resonant wavelength to get broadband reflectance.

[0064] An exemplary simulated heat map is shown in FIG. 4A, comparing the reflectance of a hexagonal pillar array against pillar radius and wavelength for a pillar height of 300 nm, and 650 nm pitch. From this map, a wide band (e.g., > 0.2 pm) of high reflectance (e.g., > 90%) is observed from 1.1 pm to 1.3 pm at the pillar radius of 200 nm, for example. Such a wide response allows for structural non-uniformities without a significant change in reflected power. While this band does shift to higher wavelengths with increasing pillar radius, it can be seen that the shift is relatively small compared to the width of the response and that there is hence significant overlap of the response for the different pillar diameters. The comparatively small shift in band / center frequency indicates that the filter characteristics are robust to manufacturing deviations that may occur in scaled-up manufacture. The reflectance is expected to vary only minimally with incident angle, since it is believed to be based on individual resonances, not periodicity.

[0065] The reflectance of a hexagonal pillar array compared as a function of wavelength at a pillar radius of 200 nm is shown in a plot in FIG. 4B. The plot shows the corresponding mode profiles at 1.17 pm and 1.27 pm, similar to what is displayed in FIGS. 3C-3F.

[0066] As noted previously, the nanopattem arrays of the infrared reflectors described above can be made using RML or NIL techniques. An exemplary RML system 500 for continuous nanopatteming over large areas is shown in FIG. 5A and FIG. 5B. The RML system may, in some examples, be configured as described in Kobrin, E. Barnard, M. Brongersma, M. K. Kwak, L. J. Guo, “Rolling Mask” nanolithography - the pathway to large area and low cost nanofabrication,” SPIE Photonics West, January 2012, incorporated herein by reference. The RML system 500 includes an exposure tool 510 that includes an in-line UV light source 520 placed inside a quartz cylinder 540. A soft mask 530 made of a compliant and transparent material (such as, but not limited to polydimethylsiloxane) is wrapped around the cylinder 540. The soft mask 530 includes an array of dead holes or cylindrical indentations 570. The path difference through the mask material in between the dead holes and through the dead holes 570 creates an corresponding interference pattern with high intensity regions in between the dead holes 570. RML system 500 also includes a plate 505 that supports a substrate 560 and positions it relative to the exposure tool 510, a resist dispense station 508, a develop station 580, and a rinse station 590.

[0067] As the substrate 560 passes through the system 500, the RML process starts with coating the substrate 560 with a thin photosensitive resist layer 550 at the resist dispense station 508. Then, resist coated substrate is moved to the exposure tool 510 and the resist layer 550 is exposed to UV light through the mask 530 in accordance with the interference pattern generated by the dead holes 570, while the mask is pressed against the surface of the resist layer 550. The cylindrical mask 530 rolls over the surface of the resist layer (for example while the substrate moves through the system 500 past the exposure tool 510, for example as it is paid out by an upstream roll and taken up by a downstream roll in a roll-to-roll process), exposing the resist to UV radiation according to the interference pattern of the mask 530. Specifically, the dead holes 570 introduce a phase shift relative to the areas in between into the UV light at the resist surface and the resist layer 550 exposure occurs in the near field of light emanating from the mask 530. The resist layer 550 is then developed at develop station 580 to create a patterned resist layer, and the developed resist layer is rinsed at rinse station 590. The resist pattern 595 can be transferred to the substrate 560, e.g., by etching (e.g., but not limited to, plasma etching, wet etching) the exposed substrate through the patterned resist using the photoresist pattern 595 as an etch mask. As an alternative to etching for forming the patterned dielectric material, a functional dielectric material can be deposited over the developed resist 550, before the photoresist is removed and the deposited dielectric material can then be lifted off, leaving a pattern corresponding to the negative of the resist pattern in the dielectric material (typically referred to as a lift-off process).

EQUIVALENTS

[0068] Those skilled in the art will recognize, or be able to ascertain, using no more than routine experimentation, numerous equivalents to the specific embodiments described specifically herein. Such equivalents are intended to be encompassed in the scope of the following claims.

Claims

1. An infrared reflector, comprising: a layer comprising a dielectric material patterned to provide an array of nanostructures, the nanostructures being pillars or holes and having dimension normal to the layer in a range from 200 nm to 5,000 nm, the nanostructures having a lateral dimension in a range from 100 nm to 1,000 nm and a pitch in at least one lateral direction in a range from 300 nm to 2,000 nm, the layer having a reflectivity of 90% or more for normally incident radiation in a band of wavelengths in a range from 700 nm to 12,000 nm and the layer absorbs 5% or less of the normally incident radiation in the band of wavelengths.

2. The infrared reflector of claim 1, wherein the pillars are formed from the dielectric material.

3. The infrared reflector of claim 1, wherein the holes are formed in a continuous layer of the dielectric material.

4. The infrared reflector of any one of claim 1-3, wherein the dielectric material is an amorphous dielectric material.

5. The infrared reflector of any one of the previous claims, wherein the dielectric material comprises silicon.

6. The infrared reflector of any one of the previous claims, wherein the nanostructures are cylindrical.

7. The infrared reflector of any one of the previous claims, wherein the array has the same pitch in two different directions in the plane.

8. The infrared reflector of any one of the previous claims, wherein the reflectivity is 95% or more.

9. The infrared reflector of any one of the previous claims, wherein the reflectivity is 90% or more for non-normally incident radiation in the band of wavelengths.

10. The infrared reflector of any one of the previous claims, wherein the absorption is 2% or less for at least some normally incident radiation in the band of wavelengths.

11. The infrared reflector of any one of the previous claims, wherein the absorption is 5% or less for at least some non-normally incident radiation in the band of wavelengths.

12. The infrared reflector of any one of the previous claims, wherein the dielectric material has a refractive index of 1.5 or more.

13. The infrared reflector of any one of the previous claims, wherein the layer has a thickness of 500 nm or more.

14. The infrared reflector of any one of the previous claims, wherein the band of wavelengths is in a range from 800 nm to 2,000 nm.

15. The infrared reflector of any one of the previous claims, wherein the band of wavelengths has a bandwidth in a range from 10 nm to 500 nm.

16. The infrared reflector of any one of the previous claims, wherein the layer extends over an area of 100 cm² or more.

17. The infrared reflector of any one of the previous claims, further comprising a substrate supporting the layer.

18. The infrared reflector of claim 17, wherein the substrate is a flexible substrate or a rigid substrate.

19. The infrared reflector of claim 17, wherein the substrate comprises the dielectric material.

20. The infrared reflector of claim 17, wherein the substrate is a plastic substrate or a glass substrate.

21. A method of manufacturing the infrared reflector of any one of the previous claims, comprising forming the layer on a substrate.

22. The method of claim 21, wherein the layer is formed using nano-imprint lithography.

23. The method of claim 21, wherein the layer is formed using rolling mask lithography.