# US 11,443,765 B2 · Compact mode converter having first and second straight portions for heat-assisted magnetic recording device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,443,765 B2 - Document ID: US11443765B2 - Status: Granted - Kind: B2 - Application number: 17/221,945 - Filed: 2021-04-05 - Published: 2021-07-22 - Granted: 2022-09-13 - Earliest claimed: 2018-04-25 - Assignees: Seagate Technology LLC - Applicants: Seagate Technology LLC - Inventors: Reyad Mehfuz; Aidan Dominic Goggin; Pierre Asselin; Christopher Neil Harvey - Web page: https://patentgrep.com/patent/US11443765B2 ## CPC - G11B 5/4866: {the arm comprising an optical waveguide, e.g. for thermally-assisted recording} - G02B 6/1226: {involving surface plasmon interaction} - G02B 6/1228: {Tapered waveguides, e.g. integrated spot-size transformers (for coupling with fibres G02B6/305)} - 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 5/6088: {Optical waveguide in or on flying head} - 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) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A write head includes an input coupler configured to receive light excited by a light source. A waveguide core is configured to receive light from the input coupler at a fundamental transverse electric (TE00) mode. The waveguide core has a first straight portion. The waveguide core has a mode converter portion comprising a branched portion extending from the first straight portion. The mode converter portion is configured to convert the light to a higher-order (TE10) mode, the mode converter portion spaced apart from the input coupler. The waveguide core has a second straight portion between the mode converter portion and a media-facing surface. The write head has a near-field transducer at the media-facing surface, the near-field transducer receiving the light at the TE10 mode from the waveguide and directing surface plasmons to a recording medium in response thereto. ## Claims ### Claim 1 A write head comprising: an input coupler configured to receive light excited by a light source; a waveguide core configured to receive light from the input coupler at a fundamental transverse electric (TE00) mode, the waveguide core comprising: a first straight portion extending from the input coupler; a mode converter portion comprising a branched portion extending from the first straight portion, the mode converter portion configured to convert the light to a higher-order (TE10) mode, the mode converter portion separated from the input coupler by the first straight portion such that the mode converter is moved out of the input coupler; and a second straight portion between the mode converter portion and a media-facing surface, wherein the first straight portion has a length greater than that of the second straight portion; and a near-field transducer at the media-facing surface, the near-field transducer configured to receive the light at the TE10 mode from the waveguide and direct surface plasmons to a recording medium in response thereto. ### Claim 2 (depends on 1) The write head of claim 1, wherein the branched portion is separated from at least part of the first straight portion by a gap for a predetermined length. ### Claim 3 (depends on 2) The write head of claim 2, wherein the gap has a substantially constant cross-sectional width. ### Claim 4 (depends on 1) The write head of claim 1, wherein the branched portion comprises a taper. ### Claim 5 (depends on 1) The write head of claim 1, wherein the second straight portion and the branched portion combine to form a predetermined combined width. ### Claim 6 (depends on 5) The write head of claim 5, wherein one or both of the second straight portion and the branched portion has a taper to accommodate the difference in the combined width. ### Claim 7 (depends on 6) The write head of claim 6, wherein the taper has a length in a range of about 2 μm to about 8 μm. ### Claim 8 (depends on 1) The write head of claim 1, wherein the mode converter portion has a length in a range of about 15 μm to about 24 μm. ### Claim 9 (depends on 1) The write head of claim 1, wherein the mode converter portion has a length of about 17 μm. ### Claim 10 (depends on 1) The write head of claim 1, wherein the light source comprises an active region formed a non-self supporting, crystalline layer transfer printed to a substrate of the write head. ### Claim 11 (depends on 1) The write head of claim 1, wherein the waveguide core is configured to receive the light emitted in a crosstrack direction from the light source. ### Claim 12 (depends on 11) The write head of claim 11, wherein the waveguide core comprises: a first turn that receives the light in the crosstrack direction redirects the light to an opposite crosstrack direction; a second turn that redirects the light to a direction normal to a media-facing surface of the write head; a first straight portion coupling the first and second turns; and a second straight portion between the second turn and the media-facing surface. ### Claim 13 A write head comprising: an input coupler configured to receive light excited by a light source; a waveguide core configured to receive light from the input coupler at a fundamental transverse electric (TE00) mode, the waveguide core comprising: an input portion extending from the input coupler and configured to receive light from the input coupler; a mode converter portion comprising a branched portion extending from the input portion, the mode converter portion configured to convert the light to a higher-order (TE10) mode, the mode converter potion separated from the input coupler by the input portion such that the mode converter is moved out of the input coupler; and an output portion between the mode converter portion and a media-facing surface, wherein the input portion has a length greater than that of the output portion; and a near-field transducer at the media-facing surface, the near-field transducer configured to receive the light at the TE10 to mode from the waveguide and direct surface plasmons to a recording medium in response thereto. ### Claim 14 (depends on 13) The write head of claim 13, wherein the mode converter portion comprises a main branch and a secondary branch, the main branch at least partially separated from the secondary branch by a by a gap for a predetermined length. ### Claim 15 (depends on 14) The write head of claim 14, wherein the gap has a substantially constant cross-sectional width. ### Claim 16 (depends on 14) The write head of claim 14, wherein the main branch and the secondary branch combine to form a predetermined combined width. ### Claim 17 (depends on 16) The write head of claim 16, wherein one or both of the main branch and the secondary branch has a taper to accommodate the difference in the combined width. ### Claim 18 (depends on 17) The write head of claim 17, wherein the taper has a length in a range of about 2 μm to about 8 μm. ### Claim 19 (depends on 13) The write head of claim 13, wherein the mode converter portion has a length in a range of about 15 μm to about 24 μm. ### Claim 20 (depends on 13) The write head of claim 13, wherein the mode converter portion has a length of about 17 μm. ### Claim 21 (depends on 1) The write head of claim 1, wherein the first straight portion has a length at least twice that of the second straight portion. ### Claim 22 (depends on 13) The write head of claim 13, wherein the input portion has a length at least twice that of the output portion.