# US 11,908,499 B1 · Heat-assisted magnetic recording head with an integrated photodiode > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,908,499 B1 - Document ID: US11908499B1 - Status: Granted - Kind: B1 - Application number: 17/809,722 - Filed: 2022-06-29 - Granted: 2024-02-20 - Earliest claimed: 2022-06-29 - Assignees: Seagate Technology LLC - Applicants: Seagate Technology LLC - Inventors: Mark Gubbins; Christopher Neil Harvey; Aidan Goggin; Fadi El Hallak; Reshma Anamari Mohandas; Bryn John Howells; Scott Eugene Olson - Web page: https://patentgrep.com/patent/US11908499B1 ## CPC - G11B 5/6088: {Optical waveguide in or on flying head} - G11B 5/314: {where the layers are extra layers normally not provided in the transducing structure, e.g. optical layers (G11B5/3196 takes precedence)} - G11B 5/4866: {the arm comprising an optical waveguide, e.g. for thermally-assisted recording} - G11B 7/126: Circuits, methods or arrangements for laser control or stabilisation - G11B 13/08: using near-field interactions or transducing means and at least one other method or means for recording or reproducing - 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) ## Abstract A heat-assisted magnetic recording head includes a laser, a near-field transducer, a primary waveguide, a secondary waveguide, and a photodiode. The laser is configured to emit electromagnetic radiation. The near-field transducer is configured to focus and emit an optical near-field. The primary waveguide configured to receive the electromagnetic radiation and propagate the electromagnetic radiation toward and proximal to the near-field transducer. The secondary waveguide configured to receive a portion of the electromagnetic radiation from the primary waveguide. The photodiode configured to receive the portion of the electromagnetic radiation from the secondary waveguide and emit a signal that represents a magnitude of the electromagnetic radiation that the laser emits. ## Claims ### Claim 1 A heat-assisted magnetic recording head comprising: a laser configured to emit electromagnetic radiation; a near-field transducer configured to focus and emit an optical near-field; a primary waveguide configured to receive the electromagnetic radiation and propagate the electromagnetic radiation toward and proximal to the near-field transducer, a first end of the primary waveguide being adjacent to the laser and a second end of the primary waveguide being adjacent to the near-field transducer; a secondary waveguide configured to receive a portion of the electromagnetic radiation from the primary waveguide; and a photodiode configured to receive the portion of the electromagnetic radiation from the secondary waveguide and emit a signal that represents a magnitude of the electromagnetic radiation that the laser emits, the secondary waveguide further configured to mitigate reflections of the electromagnetic radiation from reaching the photodiode, wherein a segment of the primary waveguide that comprises the first end is coupled to a coupler that is configured to direct electromagnetic radiation emitted by the laser into the primary waveguide, the coupler including a curved optical feature that is configured to disperse stray electromagnetic radiation. ### Claim 2 (depends on 1) The heat-assisted magnetic recording head of claim 1, wherein a segment of the primary waveguide and a segment of the secondary waveguide are adjacent and substantially parallel to each other and are separated by a gap. ### Claim 3 (depends on 2) The heat-assisted magnetic recording head of claim 2, wherein a width of the gap is from approximately 50 nanometers to approximately 1 micrometers. ### Claim 4 (depends on 2) The heat-assisted magnetic recording head of claim 2, wherein the segment of the primary waveguide and the segment of the secondary waveguide are adjacent and substantially parallel to each other over a length that is less than 30 micrometers. ### Claim 5 (depends on 1) The heat-assisted magnetic recording head of claim 1, wherein a segment of the primary waveguide that comprises the second end is adjacent to the near-field transducer. ### Claim 6 (depends on 1) The heat-assisted magnetic recording head of claim 1, wherein an end of the secondary waveguide is adjacent to the photodiode. ### Claim 7 (depends on 6) The heat-assisted magnetic recording head of claim 6, wherein a segment of the secondary waveguide that comprises the end is coupled to a decoupler that is configured to direct the portion of the electromagnetic radiation into the photodiode. ### Claim 8 (depends on 6) The heat-assisted magnetic recording head of claim 6, wherein an end of the primary waveguide is adjacent to the laser, wherein a segment of the primary waveguide that comprises the end of the primary waveguide is coupled to a coupler that is configured to direct electromagnetic radiation emitted by the laser into the primary waveguide, wherein the coupler comprises an escape slab that is configured to disperse stray electromagnetic radiation, wherein the end of the secondary waveguide is a first end of the secondary waveguide, wherein the secondary waveguide further comprises a second end, and wherein a segment of the secondary waveguide that comprises the second end is coupled to the escape slab. ### Claim 9 (depends on 1) The heat-assisted magnetic recording head of claim 1, wherein the photodiode is adjacent to a grating structure that is configured to direct the portion of the electromagnetic radiation into the photodiode. ### Claim 10 A heat-assisted magnetic recording head comprising: a laser configured to emit electromagnetic radiation; a near-field transducer configured to focus and emit an optical near-field; a photodiode configured to receive a portion of the electromagnetic radiation; a primary waveguide comprising: a first segment adjacent to the laser; a second segment adjacent to the near-field transducer; and a third segment disposed between the first segment and the second segment of the primary waveguide; and a secondary waveguide comprising: a first segment adjacent to the photodiode; a second segment that is at an opposite end of the secondary waveguide from the first segment; and a third segment disposed between the first segment and the second segment of the secondary waveguide. ### Claim 11 (depends on 10) The heat-assisted magnetic recording head of claim 10, wherein the third segment of the primary waveguide and the third segment of the secondary waveguide are adjacent and substantially parallel to each other and are separated by a gap. ### Claim 12 (depends on 10) The heat-assisted magnetic recording head of claim 10, wherein the first segment of the primary waveguide is coupled to a coupler that is configured to direct the electromagnetic radiation emitted by the laser into the primary waveguide. ### Claim 13 (depends on 12) The heat-assisted magnetic recording head of claim 12, wherein the coupler includes a curved optical feature that is configured to disperse stray electromagnetic radiation. ### Claim 14 (depends on 10) The heat-assisted magnetic recording head of claim 10, wherein the first segment of the secondary waveguide is coupled to a decoupler that is configured to direct the electromagnetic radiation into the photodiode. ### Claim 15 (depends on 10) The heat-assisted magnetic recording head of claim 10, wherein the second segment of the secondary waveguide is coupled to an escape slab that is configured to disperse stray electromagnetic radiation. ### Claim 16 A heat-assisted magnetic recording head comprising: a laser configured to emit electromagnetic radiation; a near-field transducer configured to focus and emit an optical near-field; a photodiode configured to receive a portion of the electromagnetic radiation; a primary waveguide comprising: a first segment adjacent to the laser and coupled to a coupler that is configured to direct the electromagnetic radiation emitted by the laser into the primary waveguide; a second segment adjacent to the near-field transducer; and a third segment disposed between the first end and the second end of the primary waveguide; and a secondary waveguide comprising: a first segment adjacent to the photodiode; a second segment that is at an opposite end of the secondary waveguide from the first segment; and a third segment disposed between the first end and the second end of the primary waveguide, wherein the third segment of the primary waveguide and the third segment of the secondary waveguide are adjacent and substantially parallel to each other and are separated by a gap. ### Claim 17 (depends on 16) The heat-assisted magnetic recording head of claim 16, wherein the first segment of the secondary waveguide is coupled to decoupler that is configured to direct the electromagnetic radiation into the photodiode. ### Claim 18 (depends on 1) The heat-assisted magnetic recording head of claim 1, wherein the secondary waveguide includes a hooked shape at an end positioned away from the photodiode to thereby mitigate reflections of the electromagnetic radiation. ### Claim 19 (depends on 1) The heat-assisted magnetic recording head of claim 1, wherein the primary waveguide includes a mode converter branch. ### Claim 20 A heat-assisted magnetic recording head comprising: a laser configured to emit electromagnetic radiation; a near-field transducer configured to focus and emit an optical near-field; a primary waveguide configured to receive the electromagnetic radiation and propagate the electromagnetic radiation toward and proximal to the near-field transducer; a secondary waveguide configured to receive a portion of the electromagnetic radiation from the primary waveguide; and a photodiode configured to receive the portion of the electromagnetic radiation from the secondary waveguide and emit a signal that represents a magnitude of the electromagnetic radiation that the laser emits, the secondary waveguide further configured to mitigate reflections of the electromagnetic radiation from reaching the photodiode, wherein: the primary waveguide comprises an end adjacent to the laser, a segment of the primary waveguide that comprises the end of the primary waveguide is coupled to a coupler configured to direct electromagnetic radiation emitted by the laser into the primary waveguide, the coupler comprising an escape slab configured to disperse stray electromagnetic radiation, and the secondary waveguide comprises a first end and a second end, the first end being adjacent to the photodiode and a segment of the secondary waveguide that comprises the second end is coupled to the escape slab. ### Claim 21 (depends on 20) The heat-assisted magnetic recording head of claim 20, wherein a portion of the primary waveguide and a portion of the secondary waveguide are adjacent and substantially parallel to each other and are separated by a gap. ### Claim 22 (depends on 21) The heat-assisted magnetic recording head of claim 21, wherein a width of the gap is approximately 50 nanometers to approximately 1 micrometers. ### Claim 23 (depends on 21) The heat-assisted magnetic recording head of claim 21, wherein the portion of the primary waveguide and the portion of the secondary waveguide are adjacent and substantially parallel to each other over a length that is less than 30 micrometers. ### Claim 24 (depends on 20) The heat-assisted magnetic recording head of claim 20, wherein the photodiode is adjacent to a grating structure that is configured to direct the portion of the electromagnetic radiation into the photodiode.