Assist core for spot-size transducer for heat-assisted magnetic recording

Abstract

The spot size converter (SSC) in the HAMR magnetic recording head assembly has multiple split-assist core structures. Each split-assist core structure includes multiple assist cores and a main waveguide. Each split core may also include one or more side waveguides, where the main waveguide is sandwiched between the side waveguides and between the top and bottom assist cores. Adjacent split-assist core structures may share an assist core. The split-assist core structure reduces the light source power used to write data to the magnetic media.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Non-Provisional Patent Application No. 18 / 354,439, entitled "ASSIST CORES FOR SPOT SIZE CONVERTER FOR HEAT ASSISTED MAGNETIC RECORDING," filed with the United States Patent & Trademark Office on July 18, 2023, which claims priority to U.S. Provisional Patent Application No. 63 / 506,884, filed on June 8, 2023, the entire contents of which are incorporated herein by reference for all purposes.

[0002] FIELD OF THE INVENTION FIELD Embodiments of the present disclosure generally relate to magnetic recording heads for magnetic media drives. [Background technology]

[0003] Central to the functionality and capabilities of computers is the storing and writing of data to data storage devices such as magnetic media drives (e.g., hard disk drives (HDDs)). The amount of data processed by computers is increasing rapidly. To increase the functionality and capabilities of computers, there is a need for higher recording densities of magnetic recording media.

[0004] The recording density of magnetic recording media is 2 Tbit / in 2 To achieve high recording densities exceeding 100 kHz, the width and pitch of the written tracks are reduced, and thus the width corresponding to the magnetic recording bits encoded in each written track is reduced. One challenge in reducing the width and pitch of the written tracks is reducing the surface area of ​​the main pole of the magnetic recording write head at the media facing surface (MFS). As the main pole becomes smaller, the recording field also becomes smaller, limiting the effectiveness of the magnetic recording write head.

[0005] Heat-assisted magnetic recording (HAMR) and microwave-assisted magnetic recording (MAMR) are two types of energy-assisted magnetic recording (EAMR) technologies for improving the recording density of magnetic recording media. In HAMR, a laser source is located next to or near the writing element of a magnetic recording write head to generate heat, such as a laser source that excites a near-field transducer (NFT) to generate heat at the writing location on the magnetic recording medium.

[0006] HAMR typically utilizes edge-emitting laser diode (EELD) or vertical cavity surface-emitting laser (VCSEL) devices as the light source. With either EELD or VCSEL, the coupling efficiency between the light source and the waveguide structure can be a challenge, as source operating temperature, source lifetime, source stability, and slider operating temperature can be issues.

[0007] Therefore, there is a need in the art for improved HAMR magnetic media drives. Summary of the Invention

[0008] The spot size converter (SSC) in a HAMR magnetic recording head assembly has multiple split-assist core structures. Each split-assist core structure includes multiple assist cores and a main waveguide. Each split-assist core structure may also include one or more side waveguides, where the main waveguide is sandwiched between the side waveguides and between the top and bottom assist cores. Adjacent split-assist core structures may share an assist core. The split-assist core structure reduces the light source power used to write data to the magnetic media.

[0009] In one embodiment, a magnetic recording head assembly comprises a main pole, a near-field transducer (NFT) disposed adjacent to the main pole, and a spot size converter coupled to the NFT, the spot size converter comprising: a first waveguide coupled to the NFT; a multimodal interference (MMI) device having a first end coupled to the first waveguide and a second end; and a plurality of split assist core structures coupled to the second end, the plurality of split assist core structures extending from the MMI device to a top surface of the head assembly, the top surface being opposite a medium-facing surface (MFS) of the head assembly, each split assist core structure comprising a main waveguide and a plurality of assist cores.

[0010] In another embodiment, a spot size converter includes a waveguide; a multi-modal interference (MMI) device having a first end coupled to the first waveguide and a second end; a first main waveguide coupled to the second end and extending to a third end opposite the second end; and a second main waveguide coupled to the second end and extending to the third end; and a plurality of assist cores, wherein a first assist core of the plurality of assist cores extends from the third end toward the second end, and the first assist core is spaced from both the first main waveguide and the second main waveguide by cladding material.

[0011] In another embodiment, a magnetic recording head comprises a near field transducer and a spot size converter, the spot size converter comprising: a first waveguide having a first surface coupled to the near field transducer; a multi-modal interference (MMI) device having a first end, the first end coupled to the first waveguide, and a second end; and a plurality of split assist core structures, the plurality of split assist core structures comprising a first assist core, a second assist core, and a main waveguide coupled between the first assist core and the second assist core, the main waveguide extending from the second end to a surface opposite a medium-facing surface (MFS), the main waveguide being disposed between the first assist core and the second assist core, and the first assist core, the second assist core, and the main waveguide each comprising a first material. [Brief explanation of the drawings]

[0012] So that the above-mentioned features of the present disclosure can be understood in detail, a more particular description of the present disclosure briefly summarized above can be had by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only typical embodiments of the present disclosure and therefore should not be considered as limiting its scope, as the present disclosure may admit of other equally effective embodiments. [Figure 1]1 is a schematic, illustrative diagram of a particular embodiment of a magnetic media drive including a HAMR magnetic write head. [Figure 2] 2 is a schematic illustration of a particular embodiment of a cross-sectional side view of a HAMR write head facing a magnetic disk. [Figure 3] FIG. 1 is a schematic illustration of a spot size converter (SSC) in a magnetic recording head assembly. [Figure 4A] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 4B] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 4C] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 4D] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 4E] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 4F] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 4G] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 5A] 1A-1C are schematic, illustrative diagrams of waveguide structures, according to various embodiments. [Figure 5B] 1A-1C are schematic, illustrative diagrams of waveguide structures, according to various embodiments. [Figure 6A] FIG. 5 is a schematic side, illustrative view of the SSC of FIGS. 4A-4G, in accordance with various embodiments. [Figure 6B] FIG. 5 is a schematic side, illustrative view of the SSC of FIGS. 4A-4G, in accordance with various embodiments. [Figure 6C] FIG. 5 is a schematic side, illustrative view of the SSC of FIGS. 4A-4G, in accordance with various embodiments. [Figure 7A] 1A-1C are schematic, illustrative diagrams of tapered waveguides in accordance with various embodiments; [Figure 7B] 1A-1C are schematic, illustrative diagrams of tapered waveguides in accordance with various embodiments; [Figure 8A] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 8B] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 8C] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 8D] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 8E] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 8F] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 8G] 1A-1C are schematic cross-sectional illustrations of an SSC, according to various embodiments. [Figure 9A] FIG. 8C is a schematic side, illustrative view of the SSC of FIGS. 8A-8G, in accordance with various embodiments. [Figure 9B] FIG. 8C is a schematic side, illustrative view of the SSC of FIGS. 8A-8G, in accordance with various embodiments.

[0013] To facilitate understanding, the same reference numbers have been used, whenever possible, to designate identical elements common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. DETAILED DESCRIPTION OF THE INVENTION

[0014] Reference will be made below to embodiments of the present disclosure. However, it should be understood that the present disclosure is not limited to the specifically described embodiments. Instead, any combination of the following features and elements, whether associated with different embodiments, is contemplated to implement and practice the present disclosure. Furthermore, although embodiments of the present disclosure may achieve advantages over other possible solutions and / or over the prior art, whether or not a particular advantage is achieved by a given embodiment does not limit the present disclosure. Accordingly, the following aspects, features, embodiments, and advantages are merely illustrative and are not considered elements or limitations of the appended claims unless expressly recited in the claim(s). Similarly, references to "the present disclosure" should not be construed as a generalization of any inventive subject matter disclosed herein, and should not be considered elements or limitations of the appended claims unless expressly recited in the claims.

[0015] The spot size converter (SSC) in the HAMR magnetic recording head assembly has multiple split-assist core structures. Each split-assist core structure includes multiple assist cores and a main waveguide. Each split-assist core structure may also include one or more side waveguides, where the main waveguide is sandwiched between the side waveguides and between the top and bottom assist cores. Adjacent split-assist core structures may share an assist core. The split-assist core structure reduces the light source power utilized to write data to the magnetic media.

[0016] 1 is a schematic, illustrative diagram of a particular embodiment of a magnetic media drive including an energy-assisted magnetic recording (EAMR) write head, such as a heat-assisted magnetic recording (HAMR). Such a magnetic media drive may be a single drive / device or may include multiple drives / devices. For ease of illustration, a single disk drive 100 according to one embodiment is shown. Disk drive 100 includes at least one rotatable magnetic recording medium 112 (often referred to as a magnetic disk 112) supported on a spindle 114 and rotated by a drive motor 118. The magnetic recording on each magnetic disk 112 is in the form of any suitable pattern of data tracks, such as an annular pattern of concentric data tracks (not shown) on magnetic disk 112.

[0017] At least one slider 113 is positioned near the magnetic disk 112. Each slider 113 supports a head assembly 121 that includes one or more read heads and one or more write heads, such as a HAMR write head. As the magnetic disk 112 rotates, the slider 113 moves radially in and out above the disk surface 122 so that the head assembly 121 can access different tracks on the magnetic disk 112 where desired data is written. Each slider 113 is attached to an actuator arm 119 by a suspension 115. The suspension 115 provides a slight spring force that urges the slider 113 toward the disk surface 122. Each actuator arm 119 is attached to an actuator 127. The actuator 127, as shown in FIG. 1, can be a voice coil motor (VCM). The VCM includes a coil that is movable within a fixed magnetic field, and the direction and speed of the coil movement are controlled by motor current signals provided by a control unit 129.

[0018] During operation of disk drive 100, the rotation of magnetic disk 112 creates an air bearing between slider 113 and disk surface 122, which exerts an upward force, or lift, on slider 113. The air bearing thus counteracts the slight spring force of suspension 115 and supports slider 113 a small, substantially constant distance away from and slightly above disk surface 122 during normal operation.

[0019] The various components of disk drive 100 are operationally controlled by control signals generated by control unit 129, such as access control signals and internal clock signals. Typically, control unit 129 includes logic control circuits, storage means, and a microprocessor. Control unit 129 generates control signals for controlling various system operations, such as drive motor control signals on line 123 and head position and seek control signals on line 128. The control signals on line 128 provide desired current profiles to optimally move and position slider 113 to the desired data track on magnetic disk 112. Write and read signals are communicated to and from head assembly 121 by recording channel 125. Particular embodiments of the magnetic media drive of FIG. 1 may further include multiple media or disks, multiple actuators, and / or multiple sliders.

[0020] 2 is a schematic, illustrative diagram of a particular embodiment of a cross-sectional side view of a HAMR write head 230 facing a magnetic disk 112. The HAMR write head 230 may correspond to a portion of the read / recording head assembly 121 described in FIG. 1 or a recording head used in other magnetic media drives. The HAMR write head 230 includes a medium-facing surface (MFS), such as an air bearing surface (ABS) or a gas bearing surface (GBS), facing the disk 112. As shown in FIG. 2, the magnetic disk 112 and the HAMR write head 230 move relatively (should change direction) in the direction indicated by arrow 282.

[0021] The HAMR write head 230 includes a main pole 236 disposed between a front return shield 234 and a rear return shield 238. The main pole 236 may include a main pole tip 237 in the MFS. The main pole tip 237 may or may not include a front taper and / or a rear taper. A coil 260 around the main pole 236 excites the main pole tip 237 to generate a write magnetic field for influencing the magnetic medium of the rotatable magnetic disk 112. The coil 260 may have a spiral structure or one or more sets of pancake structures. The front return shield 234 and / or the rear return shield 238 may act as a return pole for the main pole 236.

[0022] The magnetic disk 112 is positioned adjacent to or underneath the HAMR write head 230. The magnetic field generated by the current in the coil 260 is used to control the magnetization direction of the bits in the magnetic disk 112.

[0023] The HAMR write head 230 includes a structure for heating the magnetic disk 112 proximate to where the main pole tip 237 applies a magnetic write field to the storage medium. A waveguide 242 is positioned between the main pole 236 and the front return shield 234. The waveguide 242 may include a core layer and a cladding layer surrounding the core layer. The waveguide 242 conducts light from a source 278 of electromagnetic radiation, which may be, for example, ultraviolet, infrared, or visible light. The light source 278 may be, for example, an edge-emitting laser diode (EELD) or vertical-cavity surface-emitting laser (VCSEL) device, a laser diode, or other suitable laser light source for directing a light beam into the waveguide 242. Various known techniques for coupling the light source 278 to the waveguide 242 may be used. For example, the light source 278 may function in combination with an optical fiber and external optics for directing the light beam into the waveguide 242. Alternatively, the light source 278 can be mounted to the waveguide 242 and the light beam can be directly coupled into the waveguide 242 without the need for external optical configuration. Once the light beam is coupled into the waveguide 242, the light propagates through the waveguide and heats a portion of the media as the media moves relative to the HAMR write head 230, as indicated by arrow 282.

[0024] The HAMR write head 230 can include a near-field transducer (NFT) 284 for concentrating heat near the end of the waveguide 242. The NFT 284 is positioned in or adjacent to the waveguide 242 near or at the MFS. Light from the waveguide 242 is absorbed by the NFT 284, exciting surface plasmons. The surface plasmons travel along the outside of the NFT 284 toward the MFS, concentrating charge at the tip of the NFT 284. The charge then capacitively couples to the magnetic disk, heating a precise region of the magnetic disk 112 via Joule heating. One possible NFT 284 for a HAMR write head is a lollipop design, with a disk portion and a peg extending between the disk and the MFS. The NFT 284 can be positioned close to the main pole 236. The NFT 284 is relatively thermally isolated and absorbs a significant portion of the laser power during resonance.

[0025] The waveguide 242 may include a spot-size converter (SSC) including multiple waveguides, such as an assist waveguide, a side waveguide, and a main waveguide, and a multimodal interference (MMI) device. The present disclosure generally relates to managing and enhancing the profile of SSC. At least some of the SSC embodiments discussed herein result in significant improvements in the overall coupling efficiency between a coherent light source and a waveguide within a photonic integrated circuit (PIC) or planar waveguide circuit (PLC) of a HAMR head slider. The geometry and location of the core material / assist core channels both laterally and vertically adjacent to the central waveguide core are discussed herein. The overall field profile of the SSC can be tailored to match the field profile or mode of the coherent light source, leading to significant enhancements in the overall coupling efficiency.

[0026] Optical power from an external coherent light source (i.e., EELD, surface-emitting diode laser, VCSEL device, or fiber-coupled diode laser) is coupled into the NFT of the HAMR head slider through an SSC or mode converter. The basic design concept is to match the mode profile of the incident light source with the mode profile of the PLC at both coupling interfaces, thus maximizing the overall coupling efficiency.

[0027] FIG. 3 is a schematic, illustrative diagram of an SSC 302 in a magnetic recording head assembly 300. Assembly 300 includes a light source 304, illustratively a VCSEL array. The bottom surface of VCSEL array 304 has a laser emitter (output aperture) 306 that emits laser light. The laser light is fed into SSC 302, which includes multiple waveguides 308, an MMI device 312, and an exit waveguide 314, which in certain embodiments may be referred to as the main waveguide. Exit waveguide 314 is coupled to NFT 316. NFT 316 extends from exit waveguide 314 to MFS 318. Waveguide 308, discussed below, is a split core disposed within insulating material 310 having a lower refractive index than the split core material. In one embodiment, waveguide 314 may comprise a split core. In another embodiment, waveguide 314 may comprise a single core material.

[0028] The proposed design approach uses an inverse taper (narrow at the source and then widening away from the source) to force light from the fundamental mode of the waveguide into a lossy mode that more closely matches the size of the mode of the incident source. However, the lossy mode at the interface consists of an evanescent field that gradually decays in the transverse direction (perpendicular to the propagation direction). To better confine and control the decaying evanescent field profile, additional core layers / waveguides in both the lateral and vertical directions are used to further confine the mode and maximize the modal overlap between the source and SSC mode profiles.

[0029] Because modes are coupled to waveguide modes, adiabatic tapers and reverse tapers, discussed below with respect to Figures 7A and 7B, can be used in the main waveguide core (hereinafter 404D) and side waveguide cores (hereinafter 404C, 404E) to gradually transition power from the source mode to a single confined fundamental mode inside the main waveguide core (hereinafter 404D). The dimensions of the tapering and reverse tapering are carefully optimized to ensure that modes from the assist core waveguide are coupled into the main waveguide.

[0030] Due to limitations in laser design and configuration, the far field of the laser source is not always incident at normal incidence, and small tilts can be observed in the lateral direction. In this scenario, further optimization of the overall coupling efficiency can be obtained by tilting the entire waveguide core and matching the multi-channel assist core to this far-field tilt.

[0031] By improving the overall coupling efficiency between the light source and the waveguide, one can expect improved laser lifetime and stability (operating at lower currents and temperatures) and reduced stray light as more light is coupled into the waveguide, creating the possibility of additional light sources that were previously too low power. The assist cores 404A, 404B, and in some embodiments the side waveguides 404D, 404E, more efficiently couple light into the main waveguide 404D and thus into the NFT.

[0032] 4A-4G are schematic cross-sectional illustrations of SSCs according to various embodiments. FIG. 4A illustrates an SSC 400 having a single split-assist-core structure 408. The SSC 400 comprises multiple waveguide cores 404A-404E surrounded by cladding material 402. The waveguide cores 404A-404E may be referred to as assist core 404A, assist core 404B, side waveguide 404C, main waveguide 404D, and side waveguide 404E.

[0033] The waveguide cores 404A-404E may comprise any transparent material with a high refractive index greater than that of the cladding material. Suitable materials include Ta2O5, TiO2, Nb2O5, SiO x N y, Al2O3, Ge-doped SiO2 (when the cladding material is SiO2), or a combination thereof. A high refractive index material has a refractive index greater than 1. It should be understood that each waveguide core 404A-404E may have the same material or a different material, or a combination in which at least two waveguide cores 404A-404E have the same material that is different from the waveguide material of at least one other waveguide core 404A-404E. The cladding material 402 comprises a material having a lower refractive index than the waveguide cores 404A-404E. Specifically, the cladding material 402 may include any transparent material, such as silicon oxide, silicon dioxide, silicon nitride, silicon oxynitride, Al2O3, or a combination thereof. The cladding material 402 typically comprises an electrically insulating material.

[0034] Waveguide cores 404A-404E are shown as five separate cores, of which 404A and 404B collectively form split-assisted core structure 408. It should be understood that additional cores, as well as fewer cores, are contemplated. In the embodiment shown in FIG. 4A , split-assisted core structure 408 includes a top-assisted core 404A bonded to the top surface of cladding material 402. Top-assisted core 404A has a height A extending from the top surface, where A is about 50 nm to about 150 nm, e.g., about 100 nm. Top-assisted core 404A has a length 1 of about 2 μm to about 10 μm. Similarly, split-assisted core structure 408 includes a bottom-assisted core 404B bonded to the bottom surface of cladding material 402. The bottom assist core 404B has a height B extending from the bottom surface, where B is about 50 nm to about 150 nm, for example, about 100 nm. The bottom assist core 404B has a length H of about 2 um to about 10 um. It should be understood that A and B can be equal, or A and B can be different. Similarly, it should be understood that H and I can be equal, or H and I can be different. Thus, the top assist core 404A and the bottom assist core 404B can be substantially the same or different in material, length, and width.

[0035] 4A also illustrates three intermediate waveguide cores 404C-404E, which may be referred to as side waveguides or side cores or side assist cores 404C, 404E, and main waveguide or main core 404D. The intermediate waveguides 404C-404E each extend between but are spaced apart from the top and bottom surfaces of the cladding material 402 and have a height E, where E is about 150 nm to about 300 nm, e.g., about 260 nm. The intermediate waveguides 404C-404E each have a width G of about 80 nm to about 250 nm, e.g., about 165 nm. The intermediate waveguides 404C-404E are spaced apart by a distance F of about 200 nm to about 1500 nm, e.g., about 850 nm. The intermediate waveguides 404C-404E are spaced apart from the top surface of the cladding material 402 by a distance C of about 50 nm to about 250 nm, e.g., 150 nm. The intermediate waveguides 404C-404E are spaced apart from the bottom surface of the cladding material 402 by a distance D of about 50 nm to about 250 nm, e.g., about 150 nm. It should be understood that the intermediate waveguides 404C-404E can be substantially the same or different in material, length, and width. In addition, it should be understood that the intermediate waveguides 404C-404E can be spaced apart from the top and bottom surfaces of the cladding material 402 by different distances. Similarly, collectively, the distances C and D may vary not only among the individual intermediate waveguides 404C-404E, but also among the collective intermediate waveguides 404C-404E if the intermediate waveguides 404C-404E are substantially identical.

[0036] While FIG. 4A shows a single split-assisted core structure, FIG. 4B shows an SSC 410 having multiple split-assisted core structures 408. In the embodiment of FIG. 4B, there are two split-assisted core structures 408, each including a top-assisted core 404A, a bottom-assisted core 404B, and three intermediate waveguides 404C-E. The split-assisted core structures 408 can be identical. In one embodiment, the split-assisted core structures 408 are different. For example, the split-assisted core structures 408 can have different top-assisted cores 404A, and the top-assisted core 404A of one split-assisted core structure 408 can have a different material, height, and / or length than the top-assisted core 404A of the other split-assisted core structure 408. Similarly, the split-assist core structures 408 may have different bottom assist cores 404B, and the bottom assist core 404B of one split-assist core structure 408 may have a different material, height, and / or length than the bottom assist core 404B of the other split-assist core structure 408.

[0037] A similar arrangement may occur with respect to the intermediate waveguides 404C-404E. Specifically, it is contemplated that the intermediate waveguides 404C-404E may be identical in two split-assisted core structures 408, but the intermediate waveguides 404C-404E may be different. For example, the intermediate waveguides 404C-404E may all be identical in one split-assisted core structure 408 and identical in the other split-assisted core structure 408, but the intermediate waveguides 404C-404E of one split-assisted core structure 408 may differ from the intermediate waveguides 404C-404E of the other split-assisted core structure 408, and the differences may be with respect to material, height, width, distance from the top surface of the cladding material 402, and / or distance from the bottom surface of the cladding material 402. Similarly, the individual intermediate waveguides 404C-404E may vary within one split-assisted core structure 408 and may also vary within another split-assisted core structure 408, but the differences within the split-assisted core structures 408 may be the same between the split-assisted core structures 408 or may vary between the split-assisted core structures 408 in terms of material, height, width, distance from the top surface of the cladding material 402, and / or distance from the bottom surface of the cladding material 402.

[0038] The split-assisted core structures 408 may be spaced apart by distances represented by J, K, and L, where J represents the distance between the end of one top-assisted core 404A and the adjacent top-assisted core 404A and may be about 1 um to about 5 um. K represents the distance between the end of one intermediate waveguide (e.g., side waveguide 404E) and the end of another intermediate waveguide (e.g., side waveguide 404C) of an adjacent split-assisted core structure 408 and may be about 1 um to about 5 um. L represents the distance between the end of one bottom-assisted core 404B and the adjacent bottom-assisted core 404B and may be about 1 um to about 5 um.

[0039] FIG. 4C goes one step further than FIG. 4B. In FIG. 4C, eight split-assisted core structures 408 are shown in the SSC 420. While eight split-assisted core structures 408 are shown, it should be understood that more or fewer split-assisted core structures 408 are contemplated. Additionally, while an even number of split-assisted core structures 408 are shown, it should be understood that an odd number of split-assisted core structures 408 are contemplated. The split-assisted core structures 408 may be arranged as described above with respect to FIG. 4B in that they are identical / different both within any split-assisted core structure 408 and between any other split-assisted core structure 408. That is, one or more split-assisted core structures 408 may be substantially identical to or different from one or more other split-assisted core structures 408 with respect to the material of the top-assisted core 404A, the length of the top-assisted core 404A, the height of the top-assisted core 404A, the distance between adjacent top-assisted cores 404A, the material of the bottom-assisted core 404B, the length of the bottom-assisted core 404B, the height of the bottom-assisted core 404B, the distance between adjacent bottom-assisted cores 404B, the material of the intermediate waveguides 404C-404E, the number of intermediate waveguides 404C-404E, the height of the intermediate waveguides 404C-404E, the width of the intermediate waveguides 404C-404E, the distance between the intermediate waveguides 404C-404E, and / or the distance between the intermediate waveguides 404C-404E in adjacent split-assisted core structures 408.

[0040] In FIG. 4D, the multiple split-assisted core structures 408 differ by the SSC 430 compared to FIGS. 4B and 4C. Each split-assisted core structure 408 still has intermediate waveguides 404C-404E, but the split-assisted core structures 408 share a top-assisted core 404A and a bottom-assisted core 404B. The top-assisted core 404A has a height A, and the bottom-assisted core 404B has a height B, but the top-assisted core 404A has a length M of about 20 μm to about 80 μm. Note that the length M depends on the number of split-assisted core structures 408. If the number of split-assisted core structures 408 is less than eight, M can be smaller. If the number of split-assisted core structures 408 is greater than eight, M can be larger. Similarly, the bottom-assisted core 404B has a length N of about 20 μm to about 80 μm. It should be noted that the length N depends on the number of split-assist core structures 408. If the number of split-assist core structures 408 is less than eight, N can be smaller. If the number of split-assist core structures 408 is greater than eight, N can be larger. It should be understood that M and N can be the same or different. Likewise, it should be understood that A and B can be equal, or A and B can be different. Thus, the top assist core 404A and the bottom assist core 404B can be substantially the same or different in material, length, and height.

[0041] While eight split-assisted core structures 408 are shown, it should be understood that more or fewer split-assisted core structures are contemplated. Additionally, while an even number of split-assisted core structures 408 are shown, it should be understood that an odd number of split-assisted core structures 408 are contemplated. The split-assisted core structures 408 may be arranged as described above with respect to Figures 4B and 4C in that they are identical / different both within any split-assisted core structure 408 and between any other split-assisted core structure 408. That is, one or more split-assisted core structures 408 may differ from one or more other split-assisted core structures 408 with respect to the material of the intermediate waveguides 404C-404E, the number of intermediate waveguides 404C-404E, the height of the intermediate waveguides 404C-404E, the width of the intermediate waveguides 404C-404E, the distance between the intermediate waveguides 404C-404E, and / or the distance between the intermediate waveguides 404C-404E in adjacent split-assisted core structures 408.

[0042] 4E, multiple split assist core structures 408 have a common top assist core 404A but separate bottom assist cores 404B in the SSC 440. The top assist core 404A has a height A and a length M, while each bottom assist core 404B has a height B and a width H. It should be understood that A and B can be equal, or A and B can be different. Thus, the top assist core 404A and the bottom assist core 404B have different lengths, but can be substantially the same or different in material and height.

[0043] While eight split-assisted core structures 408 are shown, it should be understood that more or fewer split-assisted core structures are contemplated. Additionally, while an even number of split-assisted core structures 408 are shown, it should be understood that an odd number of split-assisted core structures 408 are contemplated. The split-assisted core structures 408 may be arranged as described above with respect to Figures 4B and 4C in that they are identical / different both within any split-assisted core structure 408 and between any other split-assisted core structure 408. That is, one or more split-assisted core structures 408 may differ from one or more other split-assisted core structures 408 with respect to the material of the bottom-assisted core 404B and the intermediate waveguides 404C-404E, the number of the bottom-assisted core 404B and the intermediate waveguides 404C-404E, the height of the bottom-assisted core 404B and the intermediate waveguides 404C-404E, the width of the bottom-assisted core 404B and the intermediate waveguides 404C-404E, the distance between the intermediate waveguides 404C-404E and the bottom-assisted core 404B, and / or the distance between the intermediate waveguides 404C-404E and the bottom-assisted core 404B in adjacent split-assisted core structures 408.

[0044] 4F, multiple split assist core structures 408 have a common bottom assist core 404B but separate top assist cores 404A in the SSC 450. The bottom assist cores 404B have a height B and a length N, while each top assist core 404A has a height A and a width I. It should be understood that A and B can be equal, or A and B can be different. Thus, the top assist cores 404A and bottom assist cores 404B have different lengths, but can be substantially the same or different in material and height.

[0045] While eight split-assisted core structures 408 are shown, it should be understood that more or fewer split-assisted core structures are contemplated. Additionally, while an even number of split-assisted core structures 408 are shown, it should be understood that an odd number of split-assisted core structures 408 are contemplated. The split-assisted core structures 408 may be arranged as described above with respect to Figures 4B and 4C in that they are identical / different both within any split-assisted core structure 408 and between any other split-assisted core structure 408. That is, one or more split-assisted core structures 408 may differ from one or more other split-assisted core structures 408 with respect to the materials of the top-assisted core 404A and the intermediate waveguides 404C-404E, the number of the top-assisted core 404A and the intermediate waveguides 404C-404E, the height of the top-assisted core 404A and the intermediate waveguides 404C-404E, the width of the top-assisted core 404A and the intermediate waveguides 404C-404E, the distance between the intermediate waveguides 404C-404E and the top-assisted core 404A, and / or the distance between the intermediate waveguides 404C-404E and the top-assisted core 404A in adjacent split-assisted core structures 408.

[0046] 4G, the SSC 460 has a mixture of split-assist core structures 408. Some split-assist core structures 408 have a common top assist core 404A and a separate bottom assist core 404B, while other split-assist core structures 408 have a common bottom assist core 404B and a separate top assist core 404A. Still other split-assist core structures 408 are completely separate, while other split-assist core structures have a common top assist core 404A and a bottom assist core 404B.

[0047] The split-assisted core structures 408 that share a top assist core 404A have a height A and a length M. The split-assisted core structures 408 that share a bottom assist core 404B have a height B and a length N. The split-assisted core structures 408 with an independent top assist core 404A have a height A and a length I, while the split-assisted core structures 408 with an independent bottom assist core 404B have a height B and a length H.

[0048] It should be understood that A and B can be equal, or A and B can be different. Likewise, it should be understood that M and M can be equal, or M and N can be different. Similarly, it should be understood that H and I can be equal, or H and I can be different. Thus, the top assist core 404A and the bottom assist core 404B have different lengths, but can be substantially the same or different in material, length, and height.

[0049] While eight split-assisted core structures 408 are shown, it should be understood that more or fewer split-assisted core structures are contemplated. Additionally, while an even number of split-assisted core structures 408 are shown, it should be understood that an odd number of split-assisted core structures 408 are contemplated. The split-assisted core structures 408 may be arranged as described above with respect to Figures 4B and 4C in that they are identical / different both within any split-assisted core structure 408 and between any other split-assisted core structure 408. That is, the one or more split assist-core structures 408 may be configured by various factors, such as the materials of the top assist core 404A, the bottom assist core 404B, and the intermediate waveguides 404C to 404E, the number of the top assist core 404A, the bottom assist core 404B, and the intermediate waveguides 404C to 404E, the heights of the top assist core 404A, the bottom assist core 404B, and the intermediate waveguides 404C to 404E, the widths of the top assist core 404A, the bottom assist core 404B, and the intermediate waveguides 404C to 404E, whether the top assist core 404A is independent or The split-assisted core structure 408 may differ from one or more other split-assisted core structures 408 with respect to the distance between adjacent top-assisted cores 404A, whether shared or not; the distance between adjacent bottom-assisted cores 404B, whether the bottom-assisted cores 404B are separate or shared; the distance between the intermediate waveguides 404C-404E and the top-assisted core 404A; and / or the distance between the intermediate waveguides 404C-404E and the top-assisted core 404A in adjacent split-assisted core structures 408.

[0050] While three intermediate waveguides 404C-404E are shown, it should be understood that more or fewer intermediate waveguides 404A-404E are contemplated. For example, it is contemplated that there may be a single intermediate waveguide 404D, as shown in Figures 8A-8G. Alternatively, it is contemplated that there may be two intermediate waveguides 404C, 404E.

[0051] 5A and 5B are schematic, illustrative diagrams of waveguide structures 500, 550 according to various embodiments. FIG. 5A illustrates a top view of a structure 500 having multiple split-assisted core structures 408. While three split-assisted core structures 408 are shown, it should be understood that there may be more split-assisted core structures 408. As shown in FIG. 5A, a slider has a cladding material 504, and a top surface 502 of the slider faces a light source 506 that emits light 508 toward the slider. The main core 404D of each split-assisted core structure 408 is shown as straight but is tapered, with a width that increases from the top surface 502 to the bottom surface 510. The side cores 404C, 404E may also be tapered, with a width that increases from the top surface 502 to the bottom surface 510. However, the ends of both side cores 404C, 404E can be either straight ends 512, as shown by the dashed lines, or curved ends 514. Light traveling through the side cores 404C, 404E typically does not fully couple into the main core 404D; if the side cores 404C, 404E have straight ends 512, some of the light is reflected off the ends of the side cores 404C, 404E and returns to the light source 506. The reflected light affects the light emission of the VCSEL, resulting in a change in output power. Curving the ends of the cores can reduce reflections. The radius of curvature R of the curved ends 514 can be from about 2 micrometers to about 20 micrometers. As also shown in FIG. 5A, the main core 404D extends from the top surface 502 to the bottom surface 510, while the side cores 404C, 404E, the top core 404A, and the bottom core 404E extend from the top surface 502 to locations recessed from the bottom surface 510.

[0052] 5B, in contrast, illustrates both a top view of a structure 550 having multiple split assist core structures 408 with a common top assist core 404A and bottom assist core 404B. Additionally, FIG. 5B illustrates a potential connection situation in which curved ends 514 of adjacent side assist cores 404C, 404E may be connected at a bond region 552.

[0053] 6A-6C are schematic side-view illustrations of the SSC of FIGS. 4A-4G in accordance with various embodiments. As shown in FIGS. 6A-6C, the main waveguide 404D extends a distance T from the opposite surface 602 of the MFS, while the side waveguides 404C, 404E each extend a distance S that is less than distance T. The bottom assist core 404B is not shown for clarity, but it should be understood that it has the same shape as the top assist core 404A. The reason the side waveguides 404C, 404E do not extend all the way to the main waveguide 404D is because, by the time the light has traveled the distance S within the side waveguides 404C, 404E, any light attempting to couple into the main waveguide 404D has already been coupled from the side waveguides 404C, 404E into the main waveguide 404D. Thus, while the wide waveguides 404C, 404E can have the same length as the main waveguide 404D, the length of the side waveguides 404C, 404E need not be the same length as the main waveguide 404D. As shown in FIG. 6A, the surface 604 opposite the surface 602 is substantially parallel to the surface 602. As shown in FIG. 6B, the top assist core 404A is shown to have an angled surface 604 facing the MFS. The surface 604 forms an angle α of about 5 degrees to about 70 degrees. The surface 604 is angled because light traveling through the assist cores 404A, 404B typically does not fully couple into the main waveguide 404D; if the ends of the cores were not angled, some of the light would reflect back to the light source. The angle helps couple as much light as possible from the assist cores 404A, 404B into the main waveguide 404D. The reflected light affects the light emission of the VCSEL, resulting in a change in the output power of the light source. The angle reduces the reflection.

[0054] As shown in FIG. 6C , rather than angling the surface 604, the surface 604 tapers away from the edge 608 of the surface 604 of the top assist core 404A toward the surface 602. The edge 608 is disposed the same distance S from the surface 602 as the side waveguides 404C, 404E. The tapering is at an angle α or β, where α is as discussed above and β can be from about 5 degrees to about 70 degrees. If the ends of the top or bottom assist cores 404A, 404B are tapered or angled, the length of the shortest point of the top or bottom assist cores 404A, 404B must be greater than the length of the side cores 404C, 404E, as indicated by S.

[0055] 7A and 7B are schematic, illustrative diagrams of a tapered waveguide according to various embodiments. While FIGS. 7A and 7B illustrate a main waveguide 404D, it should be understood that tapering is also applicable to the side waveguides 404C and 404E. The tapering occurs from a first end 702 of the main waveguide 404D to a second end 704 of the main waveguide 404D. The first end 702 has a width U of about 50 nm to about 100 nm, and the second end 704 has a width V of about 300 nm to about 800 nm, e.g., about 600 nm. Between the first end 702 and the second end 704, the waveguide may have a linear tapering, as shown in FIG. 7A, or a nonlinear tapering, as shown in FIG. 7B. The tapering assists in focusing light as it travels from the light source to the NFT.

[0056] Figures 8A-8G are schematic cross-sectional illustrations of SSCs 800, 810, 820, 830, 840, 850, and 860, according to various embodiments. The SSCs of Figures 8A-8G are substantially identical to the SSCs of Figures 4A-4G, except that rather than having side waveguides 404C and 404E and main waveguide 404D, the SSCs of Figures 8A-8G have main waveguide 404D and no side waveguides 404C and 404E.

[0057] Figures 9A and 9B are schematic side-view illustrations of the SSC of Figures 8A-8G, in accordance with various embodiments. The SSC of Figures 9A and 9B is substantially identical to the SSC of Figures 6A and 6B, except that rather than having side waveguides 404C and 404E and main waveguide 404D, the SSC of Figures 9A and 9B has main waveguide 404D and no side waveguides 404C and 404E.

[0058] Utilizing multiple split-assisted core structures in the SSC can stabilize the light source operating temperature, increase the light source lifetime, provide light source stability, and stabilize the slider operating temperature, thereby improving the coupling efficiency between the light source and the SSC.

[0059] In one embodiment, a magnetic recording head assembly includes a main pole, a near-field transducer (NFT) disposed adjacent to the main pole, and a spot size converter coupled to the NFT, the spot size converter comprising: a first waveguide coupled to the NFT; a multi-modal interference (MMI) device having a first end coupled to the first waveguide and a second end; and a plurality of split-assist core structures coupled to the second end, the plurality of split-assist core structures extending from the MMI device to a top surface of the head assembly, the top surface being opposite a medium-facing surface (MFS) of the head assembly, each split-assist core structure comprising a main waveguide and a plurality of assist cores. The magnetic recording head assembly further includes a vertical cavity surface-emitting laser (VCSEL) device coupled to the top surface, the VCSEL device each comprising a plurality of output apertures coupled to one of the plurality of split-assist core structures. In at least one split-assist-core structure, the multiple assist cores include a first assist core and a second assist core, and the main waveguide of at least one assist core is disposed between the first assist core and the second assist core. At least the first split-assist-core structure and the second split-assist-core structure of the multiple split-assist-core structures share an assist core. The main waveguide is tapered from the top surface of the head assembly to the second end. The tapering is a linear taper. The at least one split-assist-core structure includes a main waveguide, one or more side waveguides, and multiple assist cores, and the multiple assist cores include a top assist core and a bottom assist core, and the main waveguide and one or more side waveguides are disposed between the top assist core and the bottom assist core. The main waveguide has a length extending between the top surface and the second end of the head assembly, the length being greater than the lengths of one or more side waveguides extending between the top surface and the second end of the head assembly, the one or more side waveguides having curved ends, and the assist core has a surface facing the MFS, the surface being disposed at an angle to the MFS.The main waveguide is separated from the assist core by a cladding material, which may be one of the following materials: Ta2O5, TiO2, Nb2O5, or SiO. x N y , Al2O3, and Ge-doped SiO2. A magnetic media device comprising a magnetic recording head assembly is also disclosed.

[0060] In another embodiment, a spot size converter includes a waveguide, a multimodal interference (MMI) device having a first end coupled to the first waveguide and a second end, a first main waveguide coupled to the second end and extending to a third end opposite the second end, a second main waveguide coupled to the second end and extending to the third end, and a plurality of assist cores, a first assist core of the plurality of assist cores extending from the third end toward the second end, the first assist core being spaced apart from both the first and second main waveguides by a cladding material. The spot size converter further includes a second assist core extending from the third end toward the second end, the second assist core being spaced apart from both the first and second main waveguides by a cladding material. One or more of the first assist core and the second assist core extend to a location spaced from the second end. The first main waveguide has a first width and a first height, and the first assist core has a second width parallel to the first width and a second height parallel to the first height, the first width being smaller than the second width and the first height being larger than the second height. Also disclosed is a magnetic media device comprising a spot size converter.

[0061] In another embodiment, a magnetic recording head comprises a near field transducer and a spot size converter, the spot size converter comprising: a first waveguide having a first surface coupled to the near field transducer; a multi-modal interference (MMI) device having a first end, the first end coupled to the first waveguide, and a second end; and a plurality of split assist core structures, the plurality of split assist core structures comprising a first assist core, a second assist core, and a main waveguide coupled between the first assist core and the second assist core, the main waveguide extending from the second end to a surface opposite a medium-facing surface (MFS), the main waveguide being disposed between the first assist core and the second assist core, and the first assist core, the second assist core, and the main waveguide each comprising a first material. The first assist core, the second assist core, and the main waveguide are separated by a second material different from the first material.Also disclosed is a magnetic media device comprising a magnetic recording head.

[0062] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof, which scope is determined by the following claims.

Claims

1. 1. A magnetic recording head assembly comprising: The main pole and a near-field transducer (NFT) disposed adjacent to the main pole; a spot size converter coupled to the NFT, the spot size converter comprising: a first waveguide coupled to the NFT; a multi-modal interference (MMI) device having a first end, the first end coupled to the first waveguide, and a second end; a plurality of split-assisted core structures coupled to the second end, the plurality of split-assisted core structures extending from the MMI device to a top surface of the head assembly, the top surface being opposite a medium-facing surface (MFS) of the head assembly, each split-assisted core structure comprising a main waveguide and a plurality of assist cores.

2. 10. The magnetic recording head assembly of claim 1, further comprising a vertical cavity surface emitting laser (VCSEL) device coupled to the top surface, the VCSEL device comprising a plurality of output apertures, each coupled to one of the plurality of split-assisted core structures.

3. 2. The magnetic recording head assembly of claim 1, wherein in at least one split assist core structure, the plurality of assist cores comprises a first assist core and a second assist core, and the main waveguide of the at least one assist core is disposed between the first assist core and the second assist core.

4. The magnetic recording head assembly of claim 1 , wherein at least a first split-assisted core structure and a second split-assisted core structure of the plurality of split-assisted core structures share an assist core.

5. 2. The magnetic recording head assembly of claim 1, wherein the main waveguide is tapered from the top surface to the second end of the head assembly.

6. 6. The magnetic recording head assembly of claim 5, wherein the tapering is a linear tapering.

7. At least one split-assisted core structure comprises: A main waveguide and one or more side waveguides; The plurality of assist cores, A top assist core; a bottom assist core, wherein the main waveguide and the one or more side waveguides are disposed between the top assist core and the bottom assist core.

8. 8. The magnetic recording head assembly of claim 7, wherein the main waveguide has a length extending between the top surface and the second end of the head assembly, the length being greater than a length of the one or more side waveguides extending between the top surface and the second end of the head assembly.

9. The magnetic recording head of claim 8 , wherein the one or more side waveguides have curved ends.

10. 2. The magnetic recording head assembly of claim 1, wherein the assist core has a surface facing the MFS, the surface being disposed at an angle to the MFS.

11. The magnetic recording head assembly of claim 1 , wherein the main waveguide is spaced from the assist core by cladding material.

12. The cladding material is one of the following materials: Ta ２ O ５ , TiO ２ , Nb ２ O ５ , SiO ｘ N ｙ , Al ２ O ３ , and Ge-doped SiO ２ The magnetic recording head assembly of claim 11 , comprising one or more of:

13. A magnetic media device comprising the magnetic recording head assembly of claim 1.

14. A spot size converter, A waveguide; a multi-modal interference (MMI) device having a first end, the first end coupled to the waveguide, and a second end; a first main waveguide coupled to the second end and extending to a third end opposite the second end; a second main waveguide coupled to the second end and extending to the third end; a plurality of assist cores, a first assist core of the plurality of assist cores extending from the third end toward the second end, the first assist core being spaced apart from both the first main waveguide and the second main waveguide by a cladding material.

15. 15. The spot size converter of claim 14, wherein the plurality of assist cores further comprise a second assist core, the second assist core extending from the third end toward the second end, and the second assist core being spaced from both the first main waveguide and the second main waveguide by the cladding material.

16. The spot size converter of claim 15 , wherein one or more of the first assist core and the second assist core extend to a location spaced from the second end.

17. 15. The spot size converter of claim 14, wherein the first main waveguide has a first width and a first height, the first assist core has a second width parallel to the first width and a second height parallel to the first height, the first width being smaller than the second width and the first height being larger than the second height.

18. 15. A magnetic media device comprising the spot size converter of claim 14.

19. A magnetic recording head, a near field transducer; a spot size converter, wherein the spot size converter comprises: a first waveguide having a first surface coupled to the near field transducer; a multi-modal interference (MMI) device having a first end, the first end coupled to the first waveguide, and a second end; a plurality of split-assisted core structures, the plurality of split-assisted core structures comprising: a first assist core; a second assist core; a main waveguide coupled between the first assist core and the second assist core, the main waveguide extending from the second end to a surface opposite a medium-facing surface (MFS), the main waveguide being disposed between the first assist core and the second assist core, the first assist core, the second assist core, and the main waveguide each comprising a first material.

20. 20. The magnetic recording head of claim 19, wherein the first assist core, the second assist core, and the main waveguide are separated by a second material that is different from the first material.

21. 20. A magnetic media device comprising the magnetic recording head of claim 19.

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