# US 12,763,099 B1 · Single mode laser diode having multilayer dielectric mirror providing in-phase back facet reflection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,763,099 B1 - Document ID: US12763099B1 - Status: Granted - Kind: B1 - Application number: 19/326,255 - Filed: 2025-09-11 - Granted: 2026-10-13 - Earliest claimed: 2025-09-11 - Assignees: Seagate Technology LLC - Applicants: Seagate Technology LLC - Inventors: Supratim Basak; Danmark Ramos Pablo; Aidan Dominic Goggin - Web page: https://patentgrep.com/patent/US12763099B1 ## CPC - G11B 5/4866: {the arm comprising an optical waveguide, e.g. for thermally-assisted recording} - G11B 7/127: Lasers; Multiple laser arrays {(lasers per se H01S)} - H01S 5/0287: {Facet reflectivity} - G11B 2005/0021: {Thermally assisted recording using an auxiliary energy source for heating the recording layer locally to assist the magnetization reversal} - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) - 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 Described are laser diodes, and hard drive devices incorporating laser diodes, that include multilayer dielectric mirrors on the back facets thereof that are constructed to provide a high degree of in-phase reflectivity. Such laser diode constructions can help ensure stable single-mode laser operation, which may be useful in maintaining or increasing high areal density capability recording in heat-assisted magnetic recording applications. The described laser diodes include an encapsulant layer over at least the front and back facet, and a multilayer dielectric mirror disposed over the encapsulant layer at the back facet. The multilayer dielectric mirror includes alternating layers of high and low refractive index material, the high refractive index being higher than that of the encapsulant layer and the low refractive index being lower than that of the encapsulant layer. A layer of the low refractive index material is disposed immediately adjacent to the encapsulant layer. This construction can produce high reflectivity as well as in-phase reflections. ## Claims ### Claim 1 A faceted laser diode, comprising: an encapsulation layer covering the laser diode including a front facet and a back facet; and a multilayer dielectric mirror disposed over the encapsulation layer at the back facet, the multilayer dielectric mirror comprising alternating layers of a high refractive index material and a low refractive index material to thereby form multiple high/low index layer pairs, and in which one of the low refractive index material layers is immediately adjacent to the encapsulation layer, wherein the low refractive index material has a refractive index lower than that of the encapsulation layer, and the high refractive index material has a refractive index higher than that of the encapsulation layer. ### Claim 2 (depends on 1) The laser diode of claim 1, wherein the encapsulation layer is composed of a SiN material. ### Claim 3 (depends on 1) The laser diode of claim 1, wherein the low refractive index material is a SiOx material. ### Claim 4 (depends on 1) The laser diode of claim 1, wherein the high refractive index material is a TiOx material or a NbOx material. ### Claim 5 (depends on 1) The laser diode of claim 1, wherein the laser diode is composed of GaAs. ### Claim 6 (depends on 1) The laser diode of claim 1, wherein the multilayer dielectric mirror has at least three high/low layer pairs. ### Claim 7 (depends on 1) The laser diode of claim 1, wherein the refractive indices and thicknesses of the encapsulation layer and the layers of the multilayer dielectric mirror are selected to produce in-phase reflections. ### Claim 8 (depends on 1) The laser diode of claim 1, wherein the laser diode emits light at a wavelength, and wherein the encapsulation layer has a thickness at the back facet of about one half the wavelength in the encapsulation layer. ### Claim 9 (depends on 8) The laser diode of claim 8, wherein each layer of high refractive index material has a thickness that is about quarter the wavelength in the high refractive index material, and each layer of low refractive index material has a thickness that is about quarter the wavelength in the low refractive index material. ### Claim 10 (depends on 9) The laser diode of claim 9, wherein the wavelength is about 830 nm, the encapsulation layer is composed of a SiN material and has a thickness at the back facet of about 170 nm to about 230 nm, the low refractive index material is SiO2 and each layer of low refractive index material has a thickness of about 132 nm to about 152 nm, and the high refractive index material is TiO2 and each layer of high refractive index material has a thickness of about 76 nm to about 96 nm. ### Claim 11 (depends on 10) The laser diode of claim 10, wherein the SiN material is Si3N4. ### Claim 12 (depends on 1) The laser diode of claim 1, wherein the encapsulation layer is composed of SiN, and the front facet includes a SiO2 coating over the SiN encapsulation layer. ### Claim 13 A hard disk drive for heat-assisted magnetic recording, the hard disk drive including a heat-assisted magnetic recording head that includes a laser configured to emit light into a waveguide assisting in magnetic recording, the laser being a faceted laser diode that comprises: an encapsulation layer covering at least a front facet and a back facet of the faceted laser diode; and a multilayer dielectric mirror disposed over the encapsulation layer at the back facet, the multilayer dielectric mirror comprising alternating layers of a high refractive index material and a low refractive index material to thereby form multiple high/low index layer pairs, and in which one of the low refractive index material layers is immediately adjacent to the encapsulation layer, wherein the low refractive index material has a refractive index lower than that of the encapsulation layer, and the high refractive index material has a refractive index higher than that of the encapsulation layer. ### Claim 14 (depends on 13) The hard disk drive of claim 13, wherein the encapsulation layer is composed of a SiN material, the low refractive index material is a SiOx material, and the high refractive index material is a TiOx material or a NbOx material. ### Claim 15 (depends on 13) The hard disk drive of claim 13, wherein the laser diode is composed of GaAs. ### Claim 16 (depends on 13) The hard disk drive of claim 13, wherein the multilayer dielectric mirror has at least three high/low layer pairs. ### Claim 17 (depends on 13) The hard disk drive of claim 13, wherein the refractive indices and thicknesses of the encapsulation layer and the layers of the multilayer dielectric mirror are selected to produce in-phase reflections. ### Claim 18 (depends on 13) The hard disk drive of claim 13, wherein the laser diode emits light at a wavelength, and wherein the encapsulation layer has a thickness at the back facet of about one half the wavelength in the encapsulation layer, wherein each layer of high refractive index material has a thickness that is about quarter the wavelength in the high refractive index material, and wherein each layer of low refractive index material has a thickness that is about quarter the wavelength in the low refractive index material. ### Claim 19 (depends on 18) The hard disk drive of claim 18, wherein the wavelength is about 830 nm, the encapsulation layer is composed of a SiN material and has a thickness at the back facet of about 170 nm to about 230 nm, the low refractive index material is SiO2 and each layer of low refractive index material has a thickness of about 132 nm to about 152 nm, and the high refractive index material is TiO2 and each layer of high refractive index material has a thickness of about 76 nm to about 96 nm. ### Claim 20 (depends on 13) The hard disk drive of claim 13, wherein the encapsulation layer is composed of SiN, and the front facet includes a SiO2 coating over the SiN encapsulation layer.