# US 10,502,965 B2 · High-efficiency multiwavelength beam expander employing dielectric-enhanced mirrors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,502,965 B2 - Document ID: US10502965B2 - Status: Granted - Kind: B2 - Application number: 14/854,739 - Filed: 2015-09-15 - Published: 2016-03-17 - Granted: 2019-12-10 - Earliest claimed: 2014-09-17 - Assignees: Corning Incorporated - Applicants: Corning Incorporated - Inventors: Jue Wang - Web page: https://patentgrep.com/patent/US10502965B2 ## CPC - G02B 27/0983: {being curved} - C23C 14/083: {of refractory metals or yttrium} - C23C 14/10: Glass or silica - C23C 14/22: characterised by the process of coating - G02B 1/10: Optical coatings produced by application to, or surface treatment of, optical elements (G02B1/08 takes precedence) - G02B 5/0833: {comprising inorganic materials only} - G02B 5/0858: {the reflecting layers comprising a single metallic layer with one or more dielectric layers} - G02B 5/0891: {Ultraviolet [UV] mirrors (apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06)} - G02B 19/0023: {at least one surface having optical power} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04) ## Abstract A high-efficiency, multiwavelength beam-expander optical system that employs dielectric-enhanced mirrors is disclosed. Each mirror includes a reflective multilayer coating formed from alternating layers of HfO2 and SiO2 that define, in order from the substrate surface, at least first and second sections, wherein the HfO2/SiO2 layer thicknesses are generally constant within a given section and get smaller section by section moving outward from the substrate surface. The first and second sections are respectively configured to optimally reflect different operating wavelengths so that the beam-expander optical system has an optical transmission of greater than 95% at the different operating wavelengths. ## Claims ### Claim 1 A beam-expander optical system, comprising: a convex mirror having a first mirror substrate made of a metal and having a convex substrate surface and a first reflective multilayer coating formed on the convex substrate surface; a concave mirror having a second mirror substrate made of the metal and having a concave substrate surface and a second reflective multilayer coating formed on the concave substrate surface, with the convex and concave mirrors being arranged in an off-axis, afocal configuration having greater than unity magnification; wherein the first and second reflective multilayer coatings each includes alternating layers of HfO2 and SiO2 that define at least first and second sections S1 and S2, wherein the first section S1 has a layer of SiO2 immediately adjacent the convex or concave substrate surface and is configured to optimally reflect an infrared (IR) wavelength of light and substantially transmit mid-wavelength IR (MWIR) light, wherein the second section S2 resides atop the first section and is configured to optimally reflect a visible wavelength of light and wherein the second section S2 substantially transmits the MWIR light; and wherein the beam-expander optical system has an optical transmittance TBE>95% for the IR and visible wavelengths of light. ### Claim 2 (depends on 1) The beam-expander optical system according to claim 1, wherein the first and second reflective multilayer coatings each include: a third section S3 atop the second section S2 and configured to optimally reflect a ultraviolet (UV) wavelength of light and substantially transmit the MWIR light to define an optical transmittance TBE>95% at the UV wavelength of light. ### Claim 3 (depends on 1) The beam-expander optical system according to claim 1, wherein the metal is an aluminum alloy that defines a housing, and wherein the first and second mirror substrates are formed integrally with the housing. ### Claim 4 (depends on 1) The beam-expander optical system according to claim 1, wherein the first and second substrate surfaces have a root-mean-square (RMS) substrate surface roughness MSRRMS of less than 4.5 nm. ### Claim 5 (depends on 1) The beam-expander optical system according to claim 1, wherein the metal is an aluminum alloy. ### Claim 6 (depends on 2) The beam-expander optical system according to claim 2, wherein the HfO2 and SiO2 layers have respective layer thicknesses τH and τS, and wherein the layer thicknesses τH and τS in section S2 are smaller on average than those in section S1 and the layer thicknesses τH and τS in section S3 are smaller on average than those in section S2. ### Claim 7 (depends on 6) The beam-expander optical system according to claim 6, wherein: for section Si: 130 nm≤τH≤140 nm and 90 nm≤τS≤190 nm; and for section S3: 40 nm≤τH≤50 nm and 60 nm≤τS≤70 nm. ### Claim 8 (depends on 1) The beam-expander optical system according to claim 1, wherein the first and second reflective multilayer coatings each includes an uppermost capping layer of SiO2. ### Claim 9 (depends on 2) The beam-expander optical system according to claim 2, wherein each of the first and second mirrors has a reflectance R>98% at each of the UV wavelength, the VIS wavelength and the IR wavelength. ### Claim 10 A high-efficiency beam-expander optical system for use at ultraviolet (UV), visible (VIS) and infrared (IR) operating wavelengths, comprising: a first mirror with a convex substrate surface formed on a first Al alloy substrate and a second mirror with a concave substrate surface formed on a second Al alloy substrate, with the first and second mirrors arranged in an off-axis, afocal configuration having greater than unity magnification; wherein the convex and concave substrate surfaces each includes a multilayer reflective coating formed from alternating layers of HfO2 and SiO2 having respective layer thicknesses τH and τS; wherein each multilayer reflective coating includes: i) a first section having an SiO2 layer immediately adjacent the convex or concave substrate surface and configured to optimally reflect the IR operating wavelength and substantially transmit a mid-wavelength IR (MWIR) wavelength; ii) a second section atop the first section and configured to optimally reflect the VIS operating wavelength and substantially transmit the IR and MWIR operating wavelengths; and iii) a third section atop the second section and configured to optimally reflect the UV operating wavelength and substantially transmit the VIS, IR and MWIR wavelengths; and wherein the respective HfO2 and SiO2 layer thicknesses τH and τs are substantially constant within each section but are smaller in the second section on average than in the first section and in the third section on average than in the second section; and wherein the beam-expander optical system has an optical transmittance TBE>95% at the UV, the VIS and the IR operating wavelengths. ### Claim 11 (depends on 10) The high-efficiency beam-expander optical system according to claim 10, wherein the convex substrate surface and the concave substrate surface have a root-mean- square (RMS) substrate surface roughness MSRRMS of less than 4.5 nm. ### Claim 12 (depends on 10) The high-efficiency beam-expander optical system according to claim 10, wherein the UV light has an operating wavelength of 355 nm, the VIS light has an operating wavelength of 532 nm, and the IR light has an operating wavelength of 1064 nm. ### Claim 13 (depends on 10) The high-efficiency beam-expander optical system according to claim 10, further including a housing made of aluminum alloy Al-6061T1, and wherein the first and second mirror substrates are formed integrally with the housing. ### Claim 14 (depends on 10) The high-efficiency beam-expander optical system according to claim 10, wherein: the layer thicknesses τH and τS of the HfO2 and SiO2 layers in the first section are 130 nm≤τH≤140 nm and 90 nm≤τS≤190nm; and the layer thicknesses τH and τsof the HfO2 and SiO2 layers in the third section are 40 nm≤τH≤50 nm and 60 nm≤τS≤70 nm.