# US 7,466,728 B2 · Method for laterally-coupling frequency-converted laser radiation out of a resonator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,466,728 B2 - Document ID: US7466728B2 - Status: Granted - Kind: B2 - Application number: 11/484,914 - Filed: 2006-07-12 - Published: 2007-11-08 - Granted: 2008-12-16 - Earliest claimed: 2006-05-20 - Assignees: Coherent, Inc. - Inventors: David Clubley; R. Russel Austin - Web page: https://patentgrep.com/patent/US7466728B2 ## CPC - G02F 1/37: for second-harmonic generation {(G02F1/3532 takes precedence)} - G02F 1/3501: {Constructional details or arrangements of non-linear optical devices, e.g. shape of non-linear crystals} - G02F 1/3505: {Coatings; Housings; Supports} - G02F 1/3509: {Shape, e.g. shape of end face} - G02F 2203/15: involving resonance effects, e.g. resonantly enhanced interaction - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS ## Abstract In traveling-wave ring-resonator an optically nonlinear crystal for converting visible radiation to ultraviolet (UV) radiation has an input face and two output faces. The visible light propagates through the crystal from the input face to one of the output faces. That output face is coated with a dichroic optical coating that transmits unconverted visible light and reflects the ultraviolet light. The reflected ultraviolet light exits the optically nonlinear crystal via the other output face and is coupled out of the resonator at an angle to the resonator axis. ## Claims ### Claim 1 Optical apparatus comprising: an optical resonator having a resonator axis and arranged to cause a beam of optical radiation having a first-wavelength to circulate therein in one direction only along said resonator axis; and an optically nonlinear crystal located in said optical resonator on said resonator axis, said optically nonlinear crystal being arranged to convert said circulating first-wavelength wavelength radiation to optical radiation having a second wavelength shorter than said first-wavelength, and to reflectively couple said second-wavelength radiation out of said resonator at an angle to said resonator axis and wherein said optically nonlinear crystal has an input-face, and first and second output-faces and is arranged such that said circulating first wavelength radiation enters said crystal via said input face thereof and exits said optically nonlinear crystal via said first output face thereof, and such that said second-wavelength radiation is coupled out of said resonator via said second output face of said optically nonlinear crystal. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein said input face and said first output face of said optically nonlinear crystal are arranged such that circulating first-wavelength radiation is incident on said input face at about the Brewster angle and exits said first output face at about Brewster-angle incidence thereto. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein said second-wavelength radiation is incident on said second output face of said optically nonlinear crystal at about the Brewster angle. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein said second output face of said optically nonlinear crystal is inclined such that said second-wavelength radiation is incident thereon at the Brewster angle in a first plane, and incident normally thereon in a second plane perpendicular to said first plane. ### Claim 5 (depends on 1) Apparatus of claim 1, wherein said second output face of said optically nonlinear crystal is inclined such that said second-wavelength radiation is incident thereon about normally in any two mutually perpendicular planes. ### Claim 6 (depends on 5) The optically nonlinear crystal of claim 5, wherein said second output face has an antireflection coating thereon said antireflection coating arranged to minimize reflection of unpolarized second-wavelength radiation. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein said first wavelength is twice said second wavelength. ### Claim 8 (depends on 1) The apparatus of claim 1, wherein said optical resonator is a passive resonator formed by a plurality of mirrors and said optical resonator is configured such that first-wavelength radiation can be injected into said resonator via one of said plurality of mirrors to provide said circulating first-wavelength radiation. ### Claim 9 (depends on 8) The apparatus of claim 8, wherein said resonator is formed by two plane mirrors and two convex mirrors, wherein said optically nonlinear crystal is located between said convex mirrors, and wherein said first-wavelength radiation is injected into said resonator via one of said plane mirrors. ### Claim 10 Optical apparatus comprising: an optical resonator having a resonator axis and arranged to cause a beam of optical radiation having a first-wavelength to circulate therein in one direction only along said resonator axis; and an optically nonlinear crystal located in said optical resonator on said resonator axis, said crystal being arranged to convert said circulating first-wavelength wavelength radiation to optical radiation having a second wavelength shorter than said first-wavelength, and to reflectively couple said second-wavelength radiation out of said resonator at an angle to said resonator axis and wherein said crystal has an input-face, and first and second output-faces, and wherein said first output face includes an optical coating being transmissive for the first wavelength and reflective for the second wavelength and wherein said faces are arranged so that said circulating first wavelength radiation enters said crystal via said input face thereof and exits said crystal via the coating on said first output face thereof, and such that said second-wavelength radiation is coupled out of said resonator via said second output face after being reflected by said coating on the first output face. ### Claim 11 (depends on 10) The apparatus of claim 10, wherein said input face and said first output face of said optically nonlinear crystal are arranged such that circulating first-wavelength radiation is incident on said input face at about the Brewster angle and exits said first output face at about Brewster-angle incidence thereto. ### Claim 12 (depends on 10) The apparatus of claim 10, wherein said second-wavelength radiation is incident on said second output face of said optically nonlinear crystal at about the Brewster angle. ### Claim 13 (depends on 10) The apparatus of claim 10, wherein said second output face of said optically nonlinear crystal is inclined such that said second-wavelength radiation is incident thereon at the Brewster angle in a first plane, and incident normally thereon in a second plane perpendicular to said first plane. ### Claim 14 (depends on 10) Apparatus of claim 10, wherein said second output face of said optically nonlinear crystal is inclined such that said second-wavelength radiation is incident thereon about normally in any two mutually perpendicular planes. ### Claim 15 (depends on 14) The optically nonlinear crystal of claim 14, wherein said second output face has an antireflection coating thereon said antireflection coating arranged to minimize reflection of unpolarized second-wavelength radiation. ### Claim 16 (depends on 10) The apparatus of claim 10, wherein said first wavelength is twice said second wavelength. ### Claim 17 (depends on 10) The apparatus of claim 10, wherein said optical resonator is a passive resonator formed by a plurality of mirrors and said optical resonator is configured such that first-wavelength radiation can be injected into said resonator via one of said plurality of mirrors to provide said circulating first-wavelength radiation. ### Claim 18 (depends on 17) The apparatus of claim 17, wherein said resonator is formed by two plane mirrors and two convex mirrors, wherein said optically nonlinear crystal is located between said convex mirrors, and wherein said first-wavelength radiation is injected into said resonator via one of said plane mirrors. ### Claim 19 Optical apparatus comprising: an optical resonator having a resonator axis and arranged to cause a beam of optical radiation having a first-wavelength to circulate therein in one direction only along said resonator axis; and an optically nonlinear crystal located in said optical resonator on said resonator axis, said optically nonlinear crystal being arranged to convert said circulating first-wavelength wavelength radiation to optical radiation having a second wavelength shorter than said first-wavelength, and to reflectively couple said second-wavelength radiation out of said resonator at an angle to said resonator axis and wherein said optical resonator is a passive resonator formed by a plurality of mirrors and said optical resonator is configured such that first-wavelength radiation can be injected into said resonator via one of said plurality of mirrors to provide said circulating first-wavelength radiation and wherein said resonator is formed by two plane mirrors and two convex mirrors, wherein said optically nonlinear crystal is located between said convex mirrors, and wherein said first-wavelength radiation is injected into said resonator via one of said plane mirrors.