# US 2018/0025747 A1 · Heat assisted magnetic recording write apparatus having an inverse tapered waveguide > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0025747 A1 - Document ID: US20180025747A1 - Status: Published application - Kind: A1 - Application number: 15/631,299 - Filed: 2017-06-23 - Published: 2018-01-25 - Earliest claimed: 2016-07-21 - Assignees: Western Digital (Fremont), LLC - Applicants: Western Digital (Fremont), LLC - Inventors: MICHAEL V. MORELLI; SERGEI SOCHAVA - Web page: https://patentgrep.com/patent/US20180025747A1 ## CPC - G11B 5/4866: {the arm comprising an optical waveguide, e.g. for thermally-assisted recording} - 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) ## Abstract A heat assisted magnetic recording (HAMR) write apparatus has a media-facing surface (MFS) and includes a pole, coil(s) and a waveguide. The waveguide is optically coupled with a laser and directs energy toward the MFS. The waveguide includes an entrance, a bottom and a mode converter having a core, an inner cladding, high index layer(s) and an outer cladding. The core has sides that diverge in width. The core has a first index of refraction. The outer cladding has a second index of refraction less than the first index of refraction. The inner cladding has a third index of refraction not greater than the second index of refraction. The inner cladding is between the high index layer(s) and the core. The high index layer(s) are between the inner and outer cladding. The high index layer(s) have a high index of refraction greater than the second index of refraction. ## Claims ### Claim 1 A heat assisted magnetic recording write apparatus comprising: a waveguide having an entrance distal from a media facing surface of the heat assisted magnetic recording write apparatus and an exit proximate to the media facing surface, and comprising a mode converter between the entrance and the exit, wherein the waveguide is configured to direct energy from the entrance towards the exit via the mode converter in a transmission direction, and wherein the mode converter comprises a core having a first width proximate to the entrance and a second width proximate to the exit in the transmission direction, wherein the first width is less than the second width. ### Claim 2 (depends on 1) The heat assisted magnetic recording write apparatus of claim 1, wherein the mode converter further comprises an inner cladding surrounding at least portions of the core, a first high index layer abutting the inner cladding below the core in a layer direction that is perpendicular to the transmission direction, and an outer cladding surrounding at least portions of the inner cladding. ### Claim 3 (depends on 2) The heat assisted magnetic recording write apparatus of claim 2, wherein the outer cladding has an outer cladding index of refraction and the core has a core index of refraction, and wherein the outer cladding index of refraction is less than the core index of refraction. ### Claim 4 (depends on 2) The heat assisted magnetic recording write apparatus of claim 2, wherein the inner cladding has an inner cladding index of refraction and the outer cladding has an outer cladding index of refraction, and wherein the inner cladding index of refraction is less than the outer cladding index of refraction. ### Claim 5 (depends on 2) The heat assisted magnetic recording write apparatus of claim 2, wherein the first high index layer has a high index of refraction and the outer cladding has an outer cladding index of refraction and the high index of refraction is greater than the outer cladding index of refraction. ### Claim 6 (depends on 2) The heat assisted magnetic recording write apparatus of claim 2, further comprising a second high index layer above the core in the layer direction, wherein the second high index layer is between the outer cladding and the inner cladding. ### Claim 7 (depends on 6) The heat assisted magnetic recording write apparatus of claim 6, wherein the first high index layer is separated from the core by a first distance and the second high index layer is separated from the core by a second distance, and wherein the first distance is equal to the second distance. ### Claim 8 (depends on 6) The heat assisted magnetic recording write apparatus of claim 6, wherein the first high index layer is separated from the core by a first distance and the second high index layer is separated from the core by a second distance, and wherein the first distance is not equal to the second distance. ### Claim 9 (depends on 6) The heat assisted magnetic recording write apparatus of claim 6, wherein a thickness of the first high index layer is substantially similar to a thickness of the second high index layer. ### Claim 10 (depends on 6) The heat assisted magnetic recording write apparatus of claim 6, wherein a thickness of the first high index layer is different from a thickness of the second high index layer. ### Claim 11 (depends on 1) The heat assisted magnetic recording write apparatus of claim 1, wherein the energy comprises light energy having a characteristic wavelength, and wherein the first width of the core is not more than one third of the characteristic wavelength. ### Claim 12 (depends on 1) The heat assisted magnetic recording write apparatus of claim 1, wherein the energy comprises light energy having a characteristic wavelength, and wherein the second width of the core is at least one half of the characteristic wavelength. ### Claim 13 (depends on 1) The heat assisted magnetic recording write apparatus of claim 1, wherein the energy comprises light energy having a characteristic wavelength, and wherein a thickness of the core in a direction perpendicular to the transmission direction is less than the characteristic wavelength. ### Claim 14 A heat assisted magnetic recording write apparatus comprising: a waveguide optically coupled to a laser of the heat assisted magnetic recording write apparatus to transfer energy from the laser towards a media facing surface in a transmission direction, the waveguide having an entrance proximate to the laser and an exit proximate to the media facing surface, and comprising a mode converter between the entrance and the exit, wherein the mode converter comprises: a core having sides diverging from a first width proximate to the entrance to a second width proximate to the exit in the transmission direction, the first width being less than the second width and a function of a characteristic wavelength of the energy, an inner cladding surrounding at least a portion of the core, and an outer cladding surrounding at least a portion of the inner cladding. ### Claim 15 (depends on 14) The heat assisted magnetic recording write apparatus of claim 14, wherein the inner cladding has a first inner cladding width in a layer direction that is perpendicular to the transmission direction and a second inner cladding width in a direction that is perpendicular to the transmission direction and the layer direction, and wherein the first inner cladding width is at least one sixteenth of the characteristic wavelength and the second inner cladding width is at least three times the characteristic wavelength. ### Claim 16 (depends on 15) The heat assisted magnetic recording write apparatus of claim 15, further comprising a high index layer between the inner cladding and the outer cladding in the layer direction, and wherein a width of the high index layer in the layer direction is substantially similar to the second inner cladding width. ### Claim 17 (depends on 16) The heat assisted magnetic recording write apparatus of claim 16, wherein the high index layer and the inner cladding are tapered such that the width of the high index layer and the second inner cladding width proximate to the entrance is greater than the width of the high index layer and the second inner cladding width proximate to the exit. ### Claim 18 (depends on 16) The heat assisted magnetic recording write apparatus of claim 16, wherein the high index layer extends beyond the inner cladding in the transmission direction. ### Claim 19 (depends on 15) The heat assisted magnetic recording write apparatus of claim 15, wherein the outer cladding extends beyond the second inner cladding width and beyond the inner cladding in the transmission direction. ### Claim 20 A write apparatus comprising: a waveguide having an entrance distal from a media facing surface of the heat assisted magnetic recording write apparatus and an exit proximate to the media facing surface, and comprising a mode converter between the entrance and the exit, wherein the waveguide is configured to direct energy from the entrance towards the exit via the mode converter in a transmission direction, and wherein the mode converter comprises: a core having a first width proximate to the entrance and a second width that is greater than the first width proximate to the exit in the transmission direction, an inner cladding surrounding at least a portion of the core, an outer cladding surrounding at least a portion of the inner cladding, a first high index layer above the core in a direction perpendicular to the transmission direction and between the inner cladding and the outer cladding, and a second high index layer between the inner cladding and the outer cladding below the core in the layer direction.