Method and system for providing a HAMR writer having improved optical efficiency

Description

BACKGROUND

Conventional heat assisted magnetic recording (HAMR) utilizes a laser in a conjunction with magnetic recording technology to write to magnetic media in a disk drive. Light is provided from a laser to a waveguide in a HAMR transducer fabricated on a slider. The light travels through the waveguide toward the ABS and is coupled into a near-field transducer (NFT). The NFT couples light into the media at a spot size smaller than the optical diffraction limit, heating a region of the media. Coils in the transducer energize the main pole to magnetically write to a portion of the media heated by the spot size at a relatively modest field. Thus, data may be written to the media.

In order for HAMR transducers to function as desired, sufficient energy is delivered to heat the media. Various issues may affect the ability of the HAMR transducer to deliver the desired optical power to the NFT and, therefore, to the media. For example, in some cases, misalignments between the laser and the entrance of the waveguide, deformations in the waveguide, nonuniformities in the core material and/or waveguide imperfections may adversely affect the power delivered to the media. Such issues may be exacerbated in the case of a HAMR transducer using an interferometric tapered waveguide (ITWG). An ITWG splits the power provided to the waveguide into multiple arms of the waveguide. Each arm carries a portion of the laser power, or channel. The channels are recombined near the NFT where the arms come together. Changes in the phase and/or power of each channel may adversely affect the manner in which the channels recombine. Power provided to the NFT may be reduced. Accordingly, a mechanism for improving the efficiency of power delivery for a HAMR transducer is desired.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a side view of an exemplary embodiment of a HAMR disk drive.

FIG. 2 is a block diagram of a waveguide for an exemplary embodiment of a HAMR disk drive.

FIG. 3 depicts a block diagram of another exemplary embodiment of a waveguide for a HAMR disk drive.

FIG. 4 depicts an exemplary embodiment of a waveguide for a HAMR write apparatus.

FIGS. 5-8 depicts exemplary embodiments of a portion of the waveguide in a HAMR write apparatus.

FIG. 9 is a flow chart depicting an exemplary embodiment of a method for fabricating a HAMR write apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts an exemplary embodiment of a heat assisted magnetic recording (HAMR) disk drive.100. FIG. 1 is a side view of the HAMR disk drive 100. FIG. 2 is a block diagram depicting an exemplary embodiment of a waveguide 130 used in the HAMR disk drive 100. For clarity, FIGS. 1 and 2 are not to scale. For simplicity not all portions of the HAMR disk drive 100 are shown. In addition, although the HAMR disk drive 100 is depicted in the context of particular components other and/or different components may be used. For simplicity, only single components are shown. However, multiples of the component(s) and/or their sub-component(s) might be used.

The HAMR disk drive 100 includes media 102, a slider 110, a HAMR transducer 120 and a laser subassembly 190. Additional and/or different components may be included in the HAMR disk drive 100. The slider 110, the laser subassembly 190 and HAMR transducer 120 are generally attached to a suspension (not shown). The HAMR transducer 120 is fabricated on the slider 110 and includes an air-bearing surface (ABS) proximate to the media 102 during use.

In general, the HAMR disk drive 100 includes a write transducer and a read transducer. However, for clarity, only the write portion (HAMR transducer 120) of the head is shown. The HAMR transducer 120 includes optional near-field transducer (NFT) 122, a write pole 124, coil(s) 126, waveguide 130. In other embodiments, different and/or additional components may be used in the HAMR transducer 120. The laser subassembly 190 includes a laser 192, a submount 194 and an optional photodetector 196. The laser 192 may be an edge emitting laser diode. The laser subassembly 190 is generally affixed to the back side (the side opposite the ABS) of the slider 110. However, other locations are possible. The submount 194 is a substrate to which the laser 192 may be affixed for mechanical stability and ease of integration with the slider 110. The photodetector may be used to sample the light provided from the laser 192 to the HAMR transducer 120. Thus, the laser 192 may be controlled via feedback obtained from the photodetector 196. However, other configurations are possible.

The waveguide 130 is optically coupled with the laser 192 and NFT 122, which resides near the ABS. The waveguide 130 shown may be an interferometric waveguide (IWG). However, other configurations are possible. The waveguide 130 includes a mode converter 140, a mode stripper 150, an inverse tapered section 160, and an additional portion 170. The mode converter 140 is in proximity to the waveguide entrance and receives optical energy from the laser 192. The mode converter 140 has sides which taper such that the exit of the mode converter is narrower than its entrance. The mode converter aids in removing laser modes other than those which are desired to be coupled into the waveguide 130. However, some additional modes are generally present at the exit of the mode converter 140. For example, higher order modes may be present even after light has traversed the mode converter 140. Consequently, the mode converter 149 is coupled with the mode stripper 150.

The mode stripper 150 is used to suppress, or strip, some or all of the undesirable modes remaining in the laser energy after passing through the mode converter 140. In some embodiments, the fundamental mode is the desired mode for coupling into the NFT 122. Other modes extend over a larger region of the waveguide 140 in directions perpendicular to the direction of transmission. Thus, despite the use of the mode converter 140, other modes may remain. The mode stripper 150 removes some or, more preferably, all of the undesirable modes remaining. To do so, the mode stripper 150 is narrower than a remaining portion of the waveguide 130. For example, the mode stripper 170 may have a width (or area for a constant thickness) in a direction perpendicular to the transmission direction of not more than eighty percent of a remaining portion of the waveguide 130. In some embodiments, the width of the mode stripper 170 is at least sixty percent of the width of the remaining portion of the waveguide. The mode stripper also has length such that modes other than those of interest undergo at least a ninety percent loss in intensity. For example, if the fundamental mode is of interest, then the mode stripper 150 is sufficiently long that higher order modes undergo at least a ninety percent loss in power. However, the fundamental mode would undergo a loss of not more than ten percent power over the same length. In some embodiments, the length of the mode stripper is at least ten micrometers and not more than forty micrometers. Thus, the fundamental mode may be efficiently isolated and higher order modes suppressed using the mode stripper 150.

Optically coupled with the mode stripper 150 is an inverse tapered section 160. The inverse tapered section 160 increases the width (or area) of the waveguide 130 over that of the mode stripper 150. Thus, once the undesired modes have been removed, the waveguide 130 may be widened for subsequent transmission of the desired mode(s). The light is then transmitted to the remainder of the waveguide 170.

In operation, the light from the laser 192 is transmitted to the waveguide 130. The light is concentrated by the mode converter 140. As discussed above, the mode converter 140 may also remove some portion the additional modes carried by the waveguide 130. The remaining modes in the light from the laser 192 are transmitted to the mode stripper 150. As discussed above, the mode stripper 150 may rapidly and efficiently remove undesired modes from the waveguide 130. For example, the fundamental mode of the laser 192 may remain. Light is then transmitted to the remainder 170 of the waveguide 130. Light is then coupled from the waveguide 130 into the NFT 122. The NFT transfers energy to the media 102 in a desired region. The desired portion of the media 102 may be heated. Coil(s) 126 energize the pole 124, which writes to the desired portion of the media.

The HAMR disk drive 100 may have improved performance. Misalignments between the laser 192 and the waveguide 130 may result in undesired modes of laser light being coupled into the waveguide 130. The mode converter 140 may not remove all of these modes. However, these undesired modes may be more efficiently removed using the mode stripper 150. For example, the higher order modes of light from the laser 192 may be more efficiently suppressed using the mode striper 150. As a result, misalignments of the laser 192 may be accounted for. Optical efficiency of delivering light from the laser 192 to the media 102 may be enhanced. Consequently, performance of the HAMR disk drive 100 may be improved.

FIG. 3 is a block diagram depicting another embodiment of a waveguide 130′ usable in the HAMR disk drive 100. Thus, the waveguide 130′ is described in the context of the HAMR disk drive 100. For clarity, FIG. 3 is not to scale. The waveguide 130′ is analogous to the waveguide 130 and may be used in the HAMR disk drive 100. Referring to FIGS. 1 and 3, analogous portions of the waveguide 130′ are labeled similarly to the waveguide 130. The waveguide 130′ includes a mode converter 140, mode stripper 150, inverse tapered section 160 and a remaining portion 170′ that are analogous to the mode converter 140, mode stripper 150, inverse tapered section 160 and remaining portion 170 depicted in FIG. 2. Thus, the structure and function of the mode converter 140, mode stripper 150 and inverse tapered section are analogous to that described above.

The remainder 170′ of the waveguide 130′ includes a power splitter 172 and at least one interferometric waveguide (IWG) 180. The IWG may be tapered or untapered. Thus, the waveguide 130′ includes multiple arms in the IWG 180. Light from the inverse tapered section 160 is split into multiple channels using the power splitter 172. Thus, the IWG 180 includes multiple arms, each of which carries a channel. The arms of the IWG 180 may have different optical path lengths and recombine near the NFT 122. The path difference may be due to a physical path difference, a difference in optical properties of the material(s) used, some combination thereof and/or another mechanism for providing a path difference between channels. Consequently, the IWG 180 introduces a phase difference into the channels, then recombine the channels near the NFT 122. An interference pattern is thus established at or near the NFT 122. The maxima and minima of the interference pattern are provided at desired locations. Thus, energy may be coupled into the NFT 122.

The HAMR disk drive 100 using the waveguide 130′ may have improved performance. As discussed above, misalignments between the laser 192 and the waveguide 130′ may result in undesired modes being coupled into the waveguide 130′. At least some of these modes may be supported by the mode converter 140. If allowed to propagate through the waveguide 130′, these additional modes might result in additional phase and/or power differences in the arms of the IWG 180. Thus, performance of the IWG would be adversely affected. However, the mode stripper 150 may more efficiently suppress higher order modes in the waveguide 130′. The fundamental mode may thus be coupled into the power splitter 172 and IWG 180. Higher order modes that may otherwise introduce additional phase difference(s) may no longer be present and thus may not be coupled into the IWG 180. Consequently, the channels carried by the arms of the IWG 180 may have the desired phase differences and powers. Thus, the IWG 180 may function as desired. The desired power may be delivered to the NFT 122 and media 102. Thus, writing is facilitated in the HAMR disk drive 100.

FIG. 4 depicts another embodiment of a waveguide 130″ usable in the HAMR disk drive 100. Thus, the waveguide 130″ is described in the context of the HAMR disk drive 100. For clarity, FIG. 4 is not to scale. The waveguide 130″ is analogous to the waveguides 130/130′ and may be used in the HAMR disk drive 100. Referring to FIGS. 1 and 4, an NFT 122 is also shown. Analogous portions of the waveguide 130″ are labeled similarly to the waveguides 130/130′. The waveguide 130″ includes a mode converter 140′, mode stripper 150′, inverse tapered section 160′ and a remaining portion 170″ that are analogous to the mode converter 140, mode stripper 150, inverse tapered section 160 and remaining portion 170/170′ depicted in FIGS. 2-3. FIG. 4 depicts an exemplary embodiment of the geometry of the core of the waveguide 130″. Although the waveguide 130″ includes a core and cladding, for clarity, only the core is shown in FIG. 4. In the embodiment shown, the IWG 180′ specifically includes two arms 182 and 184. In some embodiments, the arms 182 and 184 are desired to introduce a particular phase difference and carry channels of equal power.

The mode converter 140′ has a curved taper. In other embodiments, the sides of the mode converter 140′ may taper in accordance with a different function. For example, the sides of the mode converter 140′ may linearly taper. The mode stripper 150′ has a width, w, and a length, l. The area of the mode stripper 150′ may be desired to be not more than eighty percent of the area of each of the arms 182 and 184. In some embodiments, the area of the mode stripper 150′ is at least sixty percent of the area of each of the arm 182 and 184. In some embodiments, the width, w, of the mode stripper 150′ is not more than eighty percent of the width of each of the arm 182 and 184. This may occur, for example, where the thickness of the waveguide (perpendicular to the plane of the page in FIG. 4) is substantially constant. In some such embodiments, the width of the mode stripper 150′ is at least sixty percent of the width of each of the arms 182 and 184. The geometry of the mode stripper 150′ is also configured such that the undesirable modes are effectively suppressed. For example, length l, of the mode stripper 150′ may also be set such that at least ninety percent of the energy of the undesirable (higher order) modes is lost as the light traverses the mode stripper 150″. In addition, not more than ten percent of the power of the desired (fundamental) mode is lost over the length l. The arms 182 and 184 of the waveguide 130″ may have optical paths of different length. Where the arms 182 and 184 recombine, near the NFT 122, the optical path difference may result in an interference pattern.

Light energy from the laser 192 is coupled into the waveguide 130″. The mode converter 140′ removes some of the additional modes present in the light entering the waveguide 130″. The mode stripper 150″ efficiently continues this process. Energy from the mode stripper 150″ is provided to the inverse tapered section 160′, which is optically coupled to the power splitter 172. Using the power splitter 172, the energy is split between the arms 182 and 184. The light travels through arms 182 and 184 and recombines near the waveguide bottom/NFT 122. As such a standing wave interference pattern may be formed. The NFT 122 couples in light from this standing wave pattern. The NFT 122 focuses the light to a region of magnetic recording media 102, which is heated. High density bits can be written on a high coercivity medium with the pole 124 energized by the coils 126 to a modest magnetic field.

The HAMR disk drive 100 using the waveguide 130″ may have improved performance. As discussed above, the mode stripper 150′ may efficiently suppress the higher order/undesirable modes of light coupled into the waveguide 130″. Thus, light having the desired phase and power may be provided to the arms 182 and 184 of the IWG 180′. Consequently, the channels carried by the arms 182 and 184 of the IWG 180′ may have the desired phase differences and powers. For example, in some embodiments, the error in the phase between the arms 182 and 184 may not exceed ten degrees. Thus, the IWG 180′ may function as desired. The desired power may be delivered to the NFT 122 and media 102. Thus, writing is facilitated in the HAMR disk drive 100.

FIGS. 5, 6, 7 and 8 depict portions of waveguides 200, 200′, 200″ and 200′″, respectively. The waveguides 200, 200′, 200″ and 200′″ correspond to the waveguides 130, 130′ and/or 130″. Thus, the waveguides 200, 200′, 200″ and 200′″ may each include a mode converter (not shown), power splitter (not shown) and IWG (not shown) corresponding to mode converter 140/140′, mode converter 170/70′, the remaining portion 170/170′/170″, including power splitter 162/162′ and IWG 180/180′. However, for clarity, only the mode stripper and inverse tapered section are shown. In particular, FIGS. 5-8 depict examples of various geometries that might be used for the mode stripper and inverse tapered section.

FIG. 5 depicts an embodiment of a portion of the waveguide 200 including the mode stripper 202 and the inverse tapered section 204. The mode stripper 202 is analogous to the mode stripper 140/140′. Thus, the length, l, width and thickness may be as described previously. The inverse tapered section 204 increases in width in accordance with a curve. The sides of the inverse tapered section 204 taper out with a function having an order greater than one. In some embodiments, the order may be two (quadratic), there (cubic) or another function.

FIG. 6 depicts an embodiment of a portion of the waveguide 200′ including the mode stripper 202′ and the inverse tapered section 204′. The mode stripper 202′ is analogous to the mode stripper 140/140′. Thus, the length, l, width and thickness may be as described previously. The sides of the inverse tapered section 204′ taper out linearly.

FIG. 7 depicts an embodiment of a portion of the waveguide 200″ including the mode stripper 202″ and the inverse tapered section 204″. The mode stripper 202″ is analogous to the mode stripper 140/140′. Thus, the length, l, width and thickness may be as described previously. The sides of the inverse tapered section 204″ taper out linearly. However, the slope of the line is different from the inverse tapered section 204′ depicted in FIG. 6. In addition, the mode stripper 202″ tapers down. Thus, the mode stripper 202″ may be viewed as including a gap 203. The gap 203 may aid in coupling light in the mode stripper 202″ to the inverse tapered section 204″.

FIG. 8 depicts an embodiment of a portion of the waveguide 200′″ including the mode stripper 202′″ and the inverse tapered section 204′″. The mode stripper 202′″ is analogous to the mode stripper 140/140′. Thus, the length, l, width and thickness may be as described previously. The sides of the inverse tapered section 204″ tapers out in accordance with a curve. In addition, the mode stripper 202″″ has a varying geometry. The mode stripper 202′″ tapers down in accordance with a curve then may taper back out slightly. Other mode strippers (not shown) might include other variations in the geometry.

Thus, the waveguides 200, 200′, 200″ and 200′″ may have geometries that differ somewhat from the geometries of the waveguides 130, 130′ and/or 130″. However, the mode strippers 202/202′/202″/202″ may still effectively suppress undesirable modes of energy. The inverse tapered sections 204/204′/204″/204′″ may also couple the mode from the mode strippers 202/202′/202″/202″ to the remainder of the waveguide. Thus, the benefits of the waveguides 130, 130′ and/or 130″ and the HAMR disk drive 100 may be achieved.

FIG. 9 is a flow chart depicting an exemplary embodiment of a method 300 for fabricating HAMR disk drives having improved optical efficiency. In particular, the method 300 may be used in fabricating a HAMR disk drive 100. For simplicity, some steps may be omitted, performed in another order, interleaved with other steps and/or combined. The method 300 is described in the context of forming a single disk drive 100. However, the method 300 may be used to fabricate multiple disk drives at substantially the same time. The method 300 and system are also described in the context of particular components. However, such components may include multiple sub-components that are also manufactured.

The write pole 124 is fabricated, via step 304. Step 304 may include forming top and/or bottom bevels in the pole tip and otherwise shaping the main pole. The coil(s) 126 may be provided, via step 304. The waveguide 130, 130′, 130″, 200, 200′, 200″ and/or 200′″ are fabricated, via step 306. Step 306 may include depositing the core layer on a cladding layer, providing a photoresist mask in the desired shape of the core for the waveguides 130/130′/130″/200/200′/200″/200′″, removing the exposed portions of the core and depositing a cladding layer. Thus, the mode converter, mode stripper, inverse tapered section, power splitter and IWG may be provided. The NFT may also be provided, via step 308. Fabrication of the transducer may then be completed.

Thus, using the method 300, the HAMR disk drive 100 and waveguides 130, 130′,130″, 200, 200′, 200′, 200′″ and/or some combination thereof may be provided. Consequently, the benefits of the waveguides 130, 130′, 130″, 200, 200′, 200′, 200′″ and mode strippers 150, 150′, 150″, 202, 202′, 202″. 202″″ may be achieved.