# US 2021/0344167 A1 · System and method for optical feedback stabilized semiconductor frequency combs > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0344167 A1 - Document ID: US20210344167A1 - Status: Published application - Kind: A1 - Application number: 17/245,242 - Filed: 2021-04-30 - Published: 2021-11-04 - Earliest claimed: 2020-05-01 - Assignees: The Trustees of Princeton University - Applicants: The Trustees of Princeton University - Inventors: Chu C. Teng; Jonas Westberg; Gerard Wysocki - Web page: https://patentgrep.com/patent/US20210344167A1 ## CPC - H01S 3/105: by controlling the mutual position or the reflecting properties of the reflectors of the cavity {, e.g. by controlling the cavity length}({H01S3/10076}, H01S3/13 take precedence) - H01S 5/0687: Stabilising the frequency of the laser - H01S 5/0622: {Controlling the frequency of the radiation} - H01S 5/14: External cavity lasers (H01S5/18 takes precedence; mode locking H01S5/065) - H01S 5/3402: {intersubband lasers, e.g. transitions within the conduction or valence bands} - H01S 3/0815: {having 3 reflectors, e.g. V-shaped resonators} - H01S 5/3401: {having no PN junction, e.g. unipolar lasers, intersubband lasers, quantum cascade lasers} - H01S 2301/02: ASE (amplified spontaneous emission), noise; Reduction thereof - H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL ## Abstract According to various embodiments, a system for stabilizing operation of semiconductor laser frequency combs via optical feedback is disclosed. The system includes an external cavity having a beam-splitter, polarizer, and mirror or partially reflective element mounted on a translational stage. The external cavity and a laser facet of the semiconductor laser form an external optical resonator for coupling light to a laser cavity. ## Claims ### Claim 1 A system for stabilizing operation of semiconductor laser frequency combs, comprising: an external cavity having a beam-splitter, polarizer, and mirror mounted on a translational stage; and a laser facet; the external cavity and laser facet forming an external optical resonator for coupling to a laser cavity. ### Claim 2 (depends on 1) The system of claim 1, wherein the laser frequency combs comprise at least one of quantum cascade lasers, interband cascade lasers, and diode lasers. ### Claim 3 (depends on 1) The system of claim 1, further comprising the laser cavity coupled to the external optical resonator. ### Claim 4 (depends on 1) The system of claim 1, wherein an external cavity length is determined by a maximum dispersion of a laser device and reflectivity of the laser facet. ### Claim 5 (depends on 1) The system of claim 1, wherein a free spectral range of a laser cavity is an integer multiple of a free spectral range of the external cavity. ### Claim 6 (depends on 1) The system of claim 1, wherein an optical feedback of the external cavity is tailored for an optimum compensation of dispersion of a laser frequency comb. ### Claim 7 (depends on 1) The system of claim 1, wherein cavity coupling and comb operation are determined by at least one of opto-mechanical, electro-optical, and acousto-optical tuning of parameters of the external cavity. ### Claim 8 A system for stabilizing operation of semiconductor laser frequency combs, comprising: an external cavity having at least one partially reflective surface mounted on a translational stage; and a laser facet; the external cavity and laser facet forming an external optical resonator for coupling to a laser cavity. ### Claim 9 (depends on 8) The system of claim 8, wherein the laser frequency combs comprise at least one of quantum cascade lasers, interband cascade lasers, and diode lasers. ### Claim 10 (depends on 8) The system of claim 8, further comprising the laser cavity coupled to the external optical resonator. ### Claim 11 (depends on 8) The system of claim 8, wherein an external cavity length is determined by a maximum dispersion of a laser device and reflectivity of the laser facet. ### Claim 12 (depends on 8) The system of claim 8, wherein a free spectral range of a laser cavity is an integer multiple of a free spectral range of the external cavity. ### Claim 13 (depends on 8) The system of claim 8, wherein the external cavity comprises multiple external cavity elements to tailor an optical feedback of the external cavity for an optimum compensation of dispersion of a laser frequency comb. ### Claim 14 (depends on 13) The system of claim 13, wherein the multiple external cavity elements comprise at least one of dielectric mirrors, metallic mirrors, lenses, diffraction gratings, prisms, and polarization optics. ### Claim 15 (depends on 13) The system of claim 13, wherein the multiple external cavity elements are coated with custom optical coatings. ### Claim 16 (depends on 8) The system of claim 8, wherein cavity coupling and comb operation are determined by at least one of opto-mechanical, electro-optical, and acousto-optical tuning of parameters of the external cavity. ### Claim 17 A method for stabilizing operation of semiconductor laser frequency combs, the method comprising: providing an external cavity having at least one partially reflective surface; and providing a laser facet; the external cavity and laser facet forming an external optical resonator for coupling to a laser cavity. ### Claim 18 (depends on 17) The method of claim 17, further comprising coupling the laser cavity to the external optical resonator. ### Claim 19 (depends on 17) The method of claim 17, further comprising determining an external cavity length by a maximum dispersion of a laser device and reflectivity of the laser facet. ### Claim 20 (depends on 17) The method of claim 17, wherein a free spectral range of a laser cavity is an integer multiple of a free spectral range of the external cavity. ### Claim 21 (depends on 17) The method of claim 17, further comprising forming the external cavity with multiple external cavity elements to tailor an optical feedback of the external cavity for an optimum compensation of dispersion of the laser frequency comb. ### Claim 22 (depends on 17) The system of claim 17, further comprising determining cavity coupling and comb operation by at least one of opto-mechanical, electro-optical, and acousto-optical tuning of parameters of the external cavity.