# US 12,119,616 B2 · Method for wavelength control of silicon photonic external cavity tunable laser > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,119,616 B2 - Document ID: US12119616B2 - Status: Granted - Kind: B2 - Application number: 18/499,471 - Filed: 2023-11-01 - Published: 2024-02-22 - Granted: 2024-10-15 - Earliest claimed: 2019-03-01 - Assignees: NeoPhotonics Corporation - Applicants: NeoPhotonics Corporation - Inventors: Yongkang Gao; Jiann-Chang Lo - Web page: https://patentgrep.com/patent/US12119616B2 ## CPC - H01S 5/141: {using a wavelength selective device, e.g. a grating or etalon (H01S5/146 takes precedence)} - H01S 5/142: {which comprises an additional resonator} - H01S 3/137: for stabilising of frequency - H01S 5/02415: {by using a thermo-electric cooler [TEC], e.g. Peltier element} - H01S 5/0612: {controlled by temperature} - H01S 5/1007: {Branched waveguides} - H01S 5/1032: {Coupling to elements comprising an optical axis that is not aligned with the optical axis of the active region} - G02B 6/12007: {forming wavelength selective elements, e.g. multiplexer, demultiplexer} - G02B 2006/12061: {Silicon} - G02B 2006/12121: {Laser} - G02B 2006/12135: {Temperature control} - H01S 3/1062: {using a controlled passive interferometer, e.g. a Fabry-Perot etalon} - H01S 5/02325: Mechanically integrated components on mount members or optical micro-benches - H01S 5/50: Amplifier structures not provided for in groups H01S5/02 - H01S5/30 - 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 - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A tunable solid state laser device are described comprising a semiconductor based gain chip and a silicon photonic filter chip with tuning capability. The silicon photonic filter chip can comprises an input-output silicon waveguide, at least two ring resonators formed with silicon waveguides, one or more connecting silicon waveguides interfacing with the ring resonators, a separate heater associated with each ring resonator, a temperature sensor configured to measure the chip temperature, and a controller connected to the temperature sensor and the separate heaters and programmed with a feedback loop to maintain the filter temperature to provide the tuned frequency. The one or more connecting silicon waveguides are configured to redirect light resonant with each of the at least two ring resonators back through the input-output silicon waveguide. Corresponding methods are described for the control of the laser frequency. Improved structures of the SiPho multiple filter chip involve a Zagnac interferometer. ## Claims ### Claim 1 An optical chip comprising: an input waveguide; a Sagnac interferometer optically connected to the input waveguide, comprising: at least two waveguide branches, and at least two ring resonators each coupled to a separate waveguide branch; at least two resistance heaters, each associated with one of the at least two ring resonators; and at least two resistance temperature sensors, each associated with one of the at least two resistance heaters, wherein a controller is connected to receive a signal from each of the at least two resistance temperature sensors to account for one or more temperature measurements in a feedback loop, and wherein a ring resonator, of the at least two ring resonators, is associated with a thermal isolation trench such that a corresponding resistance heater, a corresponding resistance temperature sensor, and the ring resonator are within a thermally isolated region from other components of the optical chip. ### Claim 2 (depends on 1) The optical chip of claim 1, wherein the thermal isolation trench undercuts the ring resonator and surrounds the ring resonator on a bottom and two sides of the ring resonator. ### Claim 3 (depends on 1) The optical chip of claim 1, wherein the corresponding resistance heater is located directly above the ring resonator. ### Claim 4 (depends on 3) The optical chip of claim 3, wherein the corresponding resistance heater is formed in a cladding layer. ### Claim 5 (depends on 3) The optical chip of claim 3, wherein a width of the corresponding resistance heater is greater than a width of the ring resonator. ### Claim 6 (depends on 1) The optical chip of claim 1, wherein the corresponding resistance temperature sensor is positioned laterally offset from, and in a same layer as, the corresponding resistance heater. ### Claim 7 (depends on 1) The optical chip of claim 1, wherein the thermal isolation trench has an arcuate shape having a curvature that substantially matches a curvature of the ring resonator. ### Claim 8 (depends on 1) The optical chip of claim 1, wherein the thermal isolation trench extends circumferentially in an arc between 30 and 90 degrees. ### Claim 9 (depends on 1) The optical chip of claim 1, wherein the thermal isolation trench extends circumferentially in an arc of at least 340 degrees. ### Claim 10 (depends on 1) The optical chip of claim 1, wherein the thermal isolation trench is a first thermal isolation trench, wherein the ring resonator is associated with a second thermal isolation trench that is located within the thermally isolated region, wherein the first thermal isolation trench has a first radius that is greater than a radius of the ring resonator, and wherein the second thermal isolation trench has a second radius that is less than the radius of the ring resonator. ### Claim 11 A tunable solid state laser device comprising: a semiconductor-based gain chip; and a silicon photonic filter chip with tuning capability, wherein the silicon photonic filter chip comprises: an input waveguide; a Sagnac interferometer optically connected to the input waveguide, comprising: at least two waveguide branches, and at least two ring resonators each coupled to a separate waveguide branch; at least two resistance heaters, each associated with one of the at least two ring resonators; and at least two resistance temperature sensors, each associated with one of the at least two resistance heaters, wherein a controller is connected to receive a signal from each of the at least two resistance temperature sensors to account for one or more temperature measurements in a feedback loop, and wherein a ring resonator, of the at least two ring resonators, is associated with a thermal isolation trench such that a corresponding resistance heater, a corresponding resistance temperature sensor, and the ring resonator are within a thermally isolated region from other components of the silicon photonic filter chip. ### Claim 12 (depends on 11) The tunable solid state laser device of claim 11, wherein the thermal isolation trench undercuts the ring resonator and surrounds the ring resonator on a bottom and two sides of the ring resonator. ### Claim 13 (depends on 11) The tunable solid state laser device of claim 11, wherein the corresponding resistance heater is located directly above the ring resonator. ### Claim 14 (depends on 13) The tunable solid state laser device of claim 13, wherein the corresponding resistance heater is formed in a cladding layer. ### Claim 15 (depends on 13) The tunable solid state laser device of claim 13, wherein a width of the corresponding resistance heater is greater than a width of the ring resonator. ### Claim 16 (depends on 11) The tunable solid state laser device of claim 11, wherein the corresponding resistance temperature sensor is positioned laterally offset from, and in a same layer as, the corresponding resistance heater. ### Claim 17 (depends on 11) The tunable solid state laser device of claim 11, wherein the thermal isolation trench has an arcuate shape having a curvature that substantially matches a curvature of the ring resonator. ### Claim 18 (depends on 11) The tunable solid state laser device of claim 11, wherein the thermal isolation trench extends circumferentially in an arc between 30 and 90 degrees. ### Claim 19 (depends on 11) The tunable solid state laser device of claim 11, wherein the thermal isolation trench extends circumferentially in an arc of at least 340 degrees. ### Claim 20 (depends on 11) The tunable solid state laser device of claim 11, wherein the thermal isolation trench is a first thermal isolation trench, wherein the ring resonator is associated with a second thermal isolation trench that is located within the thermally isolated region, wherein the first thermal isolation trench has a first radius that is greater than a radius of the ring resonator, and wherein the second thermal isolation trench has a second radius that is less than the radius of the ring resonator.