Light source unit, heat-assisted magnetic head, head gimbal assembly, and hard disk drive

Abstract

A light source unit, a heat-assisted magnetic head, a head gimbal assembly, and a hard disk drive. A light source unit includes a laser diode and a base to which the laser diode is joined. The laser diode includes a light generating layer including an active layer that emits laser light and a clad layer formed to sandwich the active layer. The active layer includes a quantum dot layer including a plurality of quantum dots having a characteristic of individually restricting movement of a carrier in three-dimensional directions.

Description

Technical Field

[0001] This invention relates to: a light source unit for recording data on a magnetic recording medium using thermally assisted magnetic recording with near-field light; a thermally assisted magnetic head; a head gimbal assembly having the thermally assisted magnetic head; and a hard disk drive. Background Technology

[0002] In recent years, with the increase in recording density of disk drives, there has been a need for thin-film magnetic heads to record data on magnetic recording media in order to further improve their performance. Composite thin-film magnetic heads are now widely used. In a composite thin-film magnetic head structure, a read head with a magnetoresistive device (hereinafter also referred to as an "MR device") for reading and a write head with an electromagnetic coil device for writing are stacked together. In a disk drive, the thin-film magnetic head is mounted on a slider that is very slightly raised from the magnetic recording medium.

[0003] Incidentally, disk drives record data by magnetizing magnetic particles on a magnetic recording medium using a write head. Making the magnetic particles smaller is effective in increasing the recording density of the magnetic recording medium.

[0004] However, as magnetic particles become smaller, their magnetization becomes unstable relative to heat due to the reduced particle size, increasing the likelihood of data loss on magnetic recording media. To address this, increasing the magnetic energy of the magnetic particles enhances magnetization stability. However, increasing the magnetic energy of the particles creates another problem: the diamagnetic force (difficulty in reverse magnetization) of the magnetic recording medium increases, thus degrading data recording performance.

[0005] To address this problem, a method called heat-assisted magnetic recording is typically proposed. When recording data on a magnetic recording medium with high antimagnetic force, a thin-film magnetic head using heat-assisted magnetic recording (hereinafter referred to as "heat-assisted head") records data while instantaneously heating and thereby raising the temperature of the portion of the magnetic recording medium where the data is to be recorded.

[0006] Because the diamagnetic strength of magnetic particles decreases with increasing temperature, data can be recorded even on magnetic recording media that have high diamagnetic strength at room temperature through momentary heating. The portion of the magnetic recording medium where data has already been recorded cools down after recording, thus increasing its diamagnetic strength. Therefore, by using a heat-assisted magnetic head, it is possible to make the magnetic particles finer and stabilize recording in a disk drive.

[0007] On the other hand, in a conventional heat-assisted magnetic head, near-field light is used as a means for heating a magnetic recording medium. When light enters an opening that is smaller than the wavelength of the light, the light slightly leaks out of the opening and locally exists near the opening. The light that locally exists near the opening is called near-field light. The near-field light is confined in a much smaller region compared to the region of a point light obtained by collecting light using a lens, and therefore, the use of the near-field light makes it possible to heat only a very small recording region of the magnetic recording medium. For example, conventional techniques regarding heat-assisted magnetic recording are disclosed in US2012-0155232 (also referred to as Patent Document 1).

[0008] Incidentally, in a heat-assisted magnetic head, because a write head is formed on a slider, a structure that directs laser light for generating near-field light to a medium facing surface of the slider is important. The following structure is generally referred to as a typical structure.

[0009] A structure in which a light source is disposed on a surface of a slider (for example, US2015-0364899 (also referred to as Patent Document 2), US2011-0205661 (also referred to as Patent Document 3), US2015-154988 (also referred to as Patent Document 4), US2015-0380035 (also referred to as Patent Document 5), JP2012-084216 (also referred to as Patent Document 6)). SUMMARY

[0010] In the case of a heat-assisted magnetic head having the above-described conventional structure, sometimes an action called "mode hopping" occurs in a laser diode that is a light source. Mode hopping is an unstable action in which an oscillation wavelength of the laser diode suddenly changes.

[0011] Because the oscillation wavelength of the laser diode suddenly changes, when mode hopping occurs, fluctuations related to light emission intensity, wavelength, phase are generated in the laser diode as noise. Then, it destabilizes the light output of the laser diode. Therefore, the recording characteristics of the heat-assisted magnetic head become unstable. Then, when data is recorded on a magnetic recording medium by the heat-assisted magnetic head, an error on the data easily occurs, and therefore, the recording quality decreases. Then, it is known that mode hopping occurs with changes in temperature, changes in optical output.

[0012] Further, it is also known that the laser diode is easily affected by temperature, that is, various characteristics of the laser diode, such as an oscillation wavelength, an optical output, an ILV characteristic curve, and the like, change with temperature. For example, in the laser diode, as indicated by I1, I2, I3 in FIG. 1, the output light intensity of the laser greatly changes with temperature. FIG. 32

[0013] ​Further, in the case of the conventional heat-assisted magnetic head, the temperature rises due to heat generated according to a data recording operation of the write head, and the temperature also rises due to heat generated according to light emission of the laser diode. In either case, since mode hopping of the laser diode occurs, the recording quality of the heat-assisted magnetic head is reduced.

[0014] That is, the laser diode sensitive to temperature is placed in an environment in which temperature change easily occurs, and in the case of the conventional heat-assisted magnetic head, it is very difficult to avoid a change in the actual operating environment temperature of the laser. Therefore, it is possible to cause mode hopping in the laser diode, thereby reducing the recording quality.

[0015] In order to prevent the recording quality from being reduced, in the heat-assisted magnetic head, it is preferable that the laser diode is not easily affected by temperature, that is, the laser diode is not sensitive to temperature.

[0016] However, in the conventional heat-assisted magnetic head, the laser diode is easily affected by temperature, and thus it is not possible to not reduce the recording quality of the heat-assisted magnetic head.

[0017] Therefore, the present application is made to solve the above problems, and the object is to stabilize the recording quality of a heat-assisted magnetic head by designing a laser diode of a light source unit so as not to be easily affected by temperature in a light source unit, a heat-assisted magnetic head having the light source unit, a head gimbal assembly, and a hard disk drive.

[0018] In order to solve the above problems, the present application is a light source unit for a heat-assisted magnetic head, the light source unit including: a laser diode; and a submount to which the laser diode is joined; the laser diode including a light generating layer including an active layer and a cladding layer, the active layer emitting laser light, the cladding layer being formed to sandwich the active layer, the active layer including a quantum dot layer including a plurality of quantum dots having a characteristic of restricting movement of a carrier in three-dimensional directions.

[0019] In the case of the above light source unit, it is possible that the active layer includes at least two quantum dot layers, and the active layer includes a multi-layer structure in which the at least two quantum dot layers are stacked.

[0020] Further, in the case of the above light source unit, it is possible that the quantum dot layer includes a low-density region, and the arrangement density of the low-density region of the quantum dot layer is smaller than that of other regions.

[0021] Further, in the case of the above light source unit, it is also possible that the laser diode includes a strip-shaped electrode formed in a straight strip shape, the quantum dot layer includes a low-density region, the arrangement density of the low-density region of the quantum dots is smaller than that of other regions, and the low-density region is arranged in a strip-shaped region corresponding to the strip-shaped electrode.

[0022] Further, it is also possible that the low-density region is arranged in a window region of the strip-shaped region, the window region corresponding to both end portions of the laser resonator.

[0023] Further, it is also possible that the laser diode includes a strip-shaped electrode formed in a straight strip shape, the multilayer structure is a structure in which window-formed quantum dot layers are stacked as quantum dot layers, the window-formed quantum dot layers include a low-density region in which the quantum dots are arranged at a lower density than in other regions, the low-density region is arranged in a window region of a strip-shaped region corresponding to the strip-shaped electrode, and the window region corresponds to both end portions of the laser resonator.

[0024] Further, it is also possible that the multilayer structure is a structure in which even-numbered dot layers and odd-numbered dot layers are alternately stacked, the even-numbered dot layers include quantum dots formed in almost the entire corresponding quantum dot layer, and the odd-numbered dot layers include a no-dot region in which no quantum dots are formed.

[0025] Further, it is possible that, in the corresponding odd-numbered dot layer, the no-dot region is arranged in a window region corresponding to both end portions of the laser resonator.

[0026] It is possible that the multilayer structure is a structure in which even-numbered dot layers and odd-numbered dot layers are stacked so that the even-numbered dot layers sandwich the odd-numbered dot layers, the even-numbered dot layers include quantum dots formed in almost the entire corresponding quantum dot layer, and the odd-numbered dot layers include a no-dot region in which no quantum dots are formed.

[0027] It is possible that the no-dot region is arranged in a center region including a center portion of the odd-numbered dot layer.

[0028] It is also possible that the quantum dot layer includes a different-size structure having a size of the quantum dots formed in the low-density region, the different-size structure having a size larger than a size of the quantum dots formed in a region other than the low-density region.

[0029] It is also possible that the quantum dot layer includes a different-composition structure having a composition of the quantum dots formed in the low-density region, the different-composition structure having a composition different from a composition of the quantum dots formed in a region other than the low-density region.

[0030] It is also possible that, in the corresponding quantum dot layer, the window region has a length longer than that of the strip-shaped region in a direction along an end surface of the active layer.

[0031] It is also possible that, in the corresponding quantum dot layer, the window region has a length longer than that of the strip-shaped region in a direction along an end surface of the active layer as the window region gradually approaches the end surface of the active layer.

[0032] Further, the present application provides a heat-assisted magnetic head including: a slider; and a light source unit joined to the slider, the slider including a slider substrate and a head portion, the head portion being formed in the slider substrate, the head portion including a waveguide, laser light emitted from the light source unit being irradiated in the waveguide, the light source unit including a laser diode and a mount, the mount joining the laser diode; the laser diode including a light generating layer, the light generating layer including an active layer and a cladding layer, the active layer emitting laser light, the cladding layer being formed so as to sandwich the active layer, the active layer including a quantum dot layer, the quantum dot layer including a plurality of quantum dots, the plurality of quantum dots having a characteristic of restricting movement of a carrier in three-dimensional directions, wherein the quantum dot layer is opposed to the waveguide.

[0033] In the case of the heat-assisted magnetic head described above, it is possible that the active layer includes a multilayer structure in which a quantum dot layer is stacked.

[0034] Further, in the case of the heat-assisted magnetic head described above, it is possible that the quantum dot layer includes a low-density region, the arrangement density of the low-density region of the quantum dot layer being smaller than that of other regions.

[0035] Further, it is possible that the laser diode includes a strip-shaped electrode formed in a straight strip shape, the quantum dot layer includes a low-density region, the arrangement density of the low-density region of the quantum dot layer being smaller than that of other regions, and the low-density region is arranged in a strip-shaped region corresponding to the strip-shaped electrode.

[0036] In this case, it is preferable that the low-density region is arranged in a window region, the window region corresponding to both end portions of the laser resonator.

[0037] Further, the present application provides a head gimbal assembly including a heat-assisted magnetic head, wherein the heat-assisted magnetic head includes: a slider; and a light source unit joined to the slider, the slider including a slider substrate and a head portion, the head portion being formed in the slider substrate, the head portion including a waveguide, laser light emitted from the light source unit being irradiated in the waveguide, the light source unit including a laser diode and a mount, the mount joining the laser diode; the laser diode including a light generating layer, the light generating layer including an active layer and a cladding layer, the active layer emitting laser light, the cladding layer being formed so as to sandwich the active layer, the active layer including a quantum dot layer, the quantum dot layer including a plurality of quantum dots, the plurality of quantum dots having a characteristic of restricting movement of a carrier in three-dimensional directions, the quantum dot layer being opposed to the waveguide.

[0038] Then, the present application provides a hard disk drive including: a head gimbal assembly having a heat-assisted magnetic head; and a magnetic recording medium opposite to the heat-assisted magnetic head, the heat-assisted magnetic head including: a slider; and a light source unit joined to the slider, the slider including a slider substrate and a head portion, the head portion being formed in the slider substrate, the head portion including a waveguide, laser light emitted from the light source unit being irradiated in the waveguide, the light source unit including a laser diode and a mount, the mount joining the laser diode; the laser diode including a light generating layer, the light generating layer including an active layer and a cladding layer, the active layer emitting the laser light, the cladding layer being formed to sandwich the active layer, the active layer including a quantum dot layer, the quantum dot layer including a plurality of quantum dots, the plurality of quantum dots having a characteristic of restricting movement of a carrier in three-dimensional directions, the quantum dot layer being opposite to the waveguide.

[0039] The present application will become more fully understood from the detailed description and the accompanying drawings, wherein: BRIEF DESCRIPTION OF DRAWINGS

[0040] FIG. 1 is a perspective view of a heat-assisted magnetic head according to an embodiment of the present application;

[0041] FIG. 2 is a side view of a heat-assisted magnetic head of an embodiment of the present application;

[0042] FIG. 3 is an enlarged perspective view of a main part of a heat-assisted magnetic head;

[0043] FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 1

[0044] FIG. 5 is a front view with parts omitted, showing an air bearing surface of a head portion;

[0045] FIG. 6 is a perspective view showing a main part of a light source unit for a heat-assisted magnetic head;

[0046] FIG. 7 is a perspective view showing a laser diode;

[0047] FIG. 8 is a perspective view showing a laser diode, to make a strip-shaped p-electrode and a strip-shaped region of an active layer clear;

[0048] FIG. 9 is a perspective view showing a light generating layer included in a laser diode;

[0049] FIG. 10 is a perspective view showing an active layer included in a heat-assisted magnetic head according to an embodiment of the present application;​

[0050] FIG. 11 is a perspective view showing the active layer as viewed from the first layer of stacked quantum dots;

[0051] FIG. 12 is a cross-sectional view taken along line 12-12 of FIG. 10

[0052] FIG. 13 is a cross-sectional view taken along line 13-13 of FIG. 10

[0053] FIG. 14 is a perspective view showing the active layer according to the first modified example;

[0054] FIG. 15 is a cross-sectional view taken along line 15-15 of FIG. 14

[0055] FIG. 16 is a cross-sectional view taken along line 16-16 of FIG. 14

[0056] FIG. 17 is a perspective view showing the active layer according to the first modified example as viewed from the first layer of stacked quantum dots;

[0057] FIG. 18 is a perspective view showing the active layer according to the first modified example, mainly showing the second layer of stacked quantum dots;

[0058] FIG. 19 is a perspective view showing the active layer according to the second modified example;

[0059] FIG. 20 is a perspective view showing the active layer according to the second modified example as viewed from the first layer of stacked quantum dots;

[0060] FIG. 21 is a perspective view showing the active layer according to the second modified example, mainly showing the second layer of stacked quantum dots;

[0061] FIG. 22 is a cross-sectional view taken along line 22-22 of FIG. 19

[0062] FIG. 23 is a cross-sectional view taken along line 23-23 of FIG. 19

[0063] is a perspective view showing the active layer according to the third modified example; FIG. 24

[0064] FIG. 25 ​​​​​​is a perspective view showing the active layer as viewed from the first stacked quantum dot layer according to a third modification example;

[0065] FIG. 26 is a cross-sectional view taken along FIG. 24 line 26-26 of FIG. 26;

[0066] FIG. 27 is a cross-sectional view taken along FIG. 24 line 27-27 of FIG. 27;

[0067] FIG. 28 is a perspective view showing the active layer as viewed from the first stacked quantum dot layer according to a fourth modification example;

[0068] FIG. 29 is a perspective view showing the active layer as viewed from the first stacked quantum dot layer according to a fifth modification example;

[0069] FIG. 30 is a perspective view showing a hard disk drive equipped with a heat-assisted magnetic head 380 according to an embodiment of the present application; FIG. 1

[0070] is a perspective view showing the back surface of the HGA; and FIG. 31

[0071] is a schematic view showing the light output intensity with respect to the current of the laser diode. FIG. 32 DETAILED DESCRIPTION

[0072] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. Note that the same parts will be denoted by the same numbers or letters, and repetitive description thereof will be omitted.

[0073] (Structure of heat-assisted magnetic head)

[0074] First, the structure of the heat-assisted magnetic head according to an embodiment of the present application will be described with reference to FIGS. 1-5 Here, FIG. 28 is a perspective view of a heat-assisted magnetic head 380 according to an embodiment of the present application, FIG. 1 FIG. 29 is a side view of the heat-assisted magnetic head 380 according to an embodiment of the present application, FIG. 2 FIG. 30 is an enlarged perspective view of a main part of the heat-assisted magnetic head 380. FIG. 3 FIG. 31 is a cross-sectional view of the main part taken along line 4-4 in FIG. 31, FIG. 4 FIG. 32 is a front view (partly omitted) showing a medium opposing surface (air bearing surface, hereinafter also referred to as "ABS") 101 of the head portion 100. FIG. 1 FIG. 5

[0075] ​​​The heat-assisted magnetic head 380 has the slider 120 and the light source unit 360 joined to the slider 120. The heat-assisted magnetic head 380 has a complex slider structure in which the light source unit 360 is joined to the slider 120. The base 350 of the light source unit 360 described later is joined to the slider 120 to constitute the heat-assisted magnetic head 380.

[0076] The slider 120 has the slider base material 110 and the head portion 100 formed on the slider base material 110.

[0077] The slider base material 110 is made of a ceramic material such as alumina-titanium carbide (Al2O3·TiC) and is formed in a rectangular parallelepiped shape. The slider base material 110 has the ABS 101 as a medium opposing surface opposite to the magnetic recording medium, and the light source placement surface 111 arranged in the back surface of the ABS 101. A part of the light source placement surface 111 on the head portion 100 side is the light source opposing surface 102. The light source opposing surface 102 opposes the laser diode 130 of the light source unit 360 described later.

[0078] The heat-assisted magnetic head 380 includes the light source unit 360, and the light source unit 360 includes the laser diode 130.

[0079] In this embodiment, the laser diode 130 includes the active layer 145 described later, and the active layer 145 includes the quantum dot layers 161 to 165 formed with a plurality of quantum dots 166. Therefore, the characteristic variation in the laser diode 130 is reduced according to the change in temperature, and the laser diode 130 is difficult to be affected by the temperature. That is, the laser diode 130 is designed to be insensitive to the temperature. Therefore, the recording quality of the heat-assisted magnetic head 380 is stable.

[0080] (Head portion)

[0081] Subsequently, the head portion 100 will be mainly described with reference to FIGS. 4-5 The head portion 100 has the read head 90 and the write head 91. The head portion 100 has a structure in which the read head 90 and the write head 91 are stacked.

[0082] The read head 90 has the MR device 5 arranged near the ABS 101 for detecting a magnetic signal. The read head 90 includes the lower shield layer 3, the lower shield gap film 4, the upper shield gap film 6, and the upper shield layer 7.

[0083] Then, an insulating layer 2 is further formed on the thin film stack surface 111a of the slider substrate 110, and a lower shield layer 3 made of a magnetic material is formed on the insulating layer 2. Further, a lower shield gap film 4 as an insulating film is formed on the lower shield layer 3, and an upper shield gap film 6 that shields the MR device 5 is formed on the lower shield gap film 4. An upper shield layer 7 made of a magnetic material is formed on the upper shield gap film 6, and an insulating layer 8 is formed on the upper shield layer 7.

[0084] The MR device 5 is composed of a magnetic sensitive film that exhibits a magnetoresistance effect, such as an AMR (Anisotropic Magneto Resistance), GMR (Giant Magneto Resistance), and TMR (Tunneling Magneto Resistance) device.

[0085] The write head 91 has a thin film coil 12, a return magnetic layer 20, a core layer 25, a lower dielectric layer 24, an upper dielectric layer 26, a near-field light generating layer 28, an overcoat layer 34, a main pole layer 40, and a link pole layer 45, and has a structure in which they are stacked on the thin film stack surface 111a.

[0086] The thin film coil 12 has four return portions. The thin film coil 12 is wound like a flat spiral on the yoke pole layer 42 of the main pole layer 40, which will be described later.

[0087] The four return portions are arranged at respective positions different in distance from the ABS 101. Among them, the return portion 12D is a portion of the four return portions of the thin film coil 12 that is arranged at a position farthest from the ABS 101. The four return portions are insulated from each other by a photoresist 13.

[0088] When a current modulated in accordance with data to be recorded on a magnetic recording medium flows through the thin film coil 12, the current causes the thin film coil 12 to generate a recording magnetic field.

[0089] The return pole layer 20 has a connection pole layer 21 and a back pole layer 22. The connection pole layer 21 has a pole end surface 21a arranged inside the ABS 101, and has a portion farther from the ABS 101 than the pole end surface 21a embedded in the insulating layer 8. The connection pole layer 21 has a size that reaches a position farther from the ABS 101 than the return portion 12D. The back pole layer 22 is joined to the connection pole layer 21 at a position farther from the ABS 101 than the return portion 12D.

[0090] The back pole layer 22 is arranged at a position farther from the ABS 101 than the return portion 12D, and is joined to the connection pole layer 21 and the link pole layer 45, which will be described later.

[0091] The return pole layer 20 is provided to return the magnetic flux to the main pole layer 40. When the magnetic flux generated by the recording magnetic field is emitted from the pole end surface 41g of the main pole layer 40 to be described later to the magnetic recording medium, the magnetic flux flows back to the return pole layer 20 (a soft magnetic layer not described in detail) via the magnetic recording medium. The magnetic flux passes through the link pole layer 45 and reaches the main pole layer 40.

[0092] The core layer 25 is a waveguide that guides the laser light generated by the laser diode 130 of the light source unit 360 from the light source opposing surface 102 to the ABS 101. As shown in FIG. 2, the core layer 25 is formed along the depth direction from the ABS 101 to the light source opposing surface 102 through between the link pole layers 45. FIG. 4

[0093] The core layer 25 is formed of a dielectric such as tantalum oxide (TaO x ) or the like. For example, the core layer 25 can be formed of Ta2O5 (for example, a refractive index of about 2.16).

[0094] The core layer 25 is formed to be housed in the recess 26c of the upper dielectric layer 26 on the upper surface 24d of the lower dielectric layer 24. In addition, the upper surface 25d and the two side surfaces of the core layer 25 are in contact with the upper dielectric layer 26, and the lower surface 25e of the core layer 25 is in contact with the lower dielectric layer 24.

[0095] Then, the upper dielectric layer 26 and the lower dielectric layer 24 are arranged around the core layer 25, and the cladding layer is composed of the upper dielectric layer 26 and the lower dielectric layer 24.

[0096] The upper dielectric layer 26 is formed in a substantially flat plate shape, and the width thereof is larger than the width of the pole end portion layer 41. The upper dielectric layer 26 is formed of a dielectric layer having a smaller refractive index than the core layer 25, for example, such as aluminum oxide (AlO x ) or the like. For example, the upper dielectric layer 26 can be formed of aluminum oxide (for example, Al2O3, a refractive index of about 1.63). Then, the recess 26c in which the core layer 25 is housed is formed on the lower surface 26e of the upper dielectric layer 26.

[0097] The lower dielectric layer 24 is formed in contact with the lower surface 25e of the core layer 25 and the lower surface 26e of the upper dielectric layer 26. Like the upper dielectric layer 26, the lower dielectric layer 24 can be formed of a dielectric such as aluminum oxide (AlO x ) or the like.

[0098] For example, the lower dielectric layer 24 can be formed of aluminum oxide (Al2O3).

[0099] The near-field light generating layer 28 has a structure formed as a rectangle as a whole when viewed from the ABS 101. ​

[0100] The near-field light generating layer 28 is made of metal, and is formed of one or more of, for example, Au, Ag, Al, Cu, Pd, Pt, Rh, Ir, or an alloy made of a plurality of these elements.

[0101] The near-field light generating layer 28 has a bottom 28c. The bottom 28c is arranged at the deepest position of the near-field light generating layer 28. The bottom 28c extends from the ABS 101 in the depth direction. An end surface of the bottom 28c on the ABS 101 side is arranged inside the ABS 101. This end surface is a generating end 28e. The generating end 28e generates near-field light for heating a magnetic recording medium.

[0102] The main pole layer 40 has a pole end layer 41 and a yoke pole layer 42. The pole end layer 41 and the yoke pole layer 42 have a symmetrical structure formed so as to be left-right symmetrical with respect to the front end 41c.

[0103] A front surface including the front end 41c constitutes a pole end surface 41g. The pole end surface 41g is arranged inside the ABS 101. The yoke pole layer 42 is joined to the upper surface 41e of the pole end layer 41.

[0104] The yoke pole layer 42 has a rear pole layer 42a, an intermediate pole layer 42b, and a front pole layer 42c. The yoke pole layer 42 has a curved structure that extends from the ABS 101 in the depth direction and passes through the link pole layer 45 across the thin-film coil 12.

[0105] The rear pole layer 42a is arranged at a position farther from the ABS 101 than the four return portions of the thin-film coil 12. The lateral width of the rear pole layer 42a is larger than the lateral width of the intermediate pole layer 42b (the largest lateral width in the yoke pole layer 42) and is joined to the link pole layer 45. The intermediate pole layer 42b is arranged above the thin-film coil 12. The intermediate pole layer 42b is connected to the rear pole layer 42a and the front pole layer 42c. The lateral width of the intermediate pole layer 42b gradually decreases as it approaches the ABS 101. The front pole layer 42c is formed as a downwardly curved structure that is closer to the pole end layer 41 as it approaches the ABS 101. The front pole layer 42c is joined to the surface 41e of the pole end layer 41.

[0106] The link pole layer 45 is arranged to hold the core layer 25 at a position farther from the ABS 101 than the thin-film coil 12 on both left and right sides. Furthermore, the link pole layer 45 is joined to the rear pole layer 22. The link pole layer 45 magnetically links the return pole layer 20 to the main pole layer 40, and has the effect of returning the magnetic flux flowing back to the return pole layer 20 to the main pole layer 40.

[0107] (Optical source unit)

[0108] Subsequently, except forFIGS. 1-5 Reference will also be made to FIGS. 6-13 The light source unit 360 will be described. Here, FIG. 6 is a perspective view showing the main part of the light source unit 360 for the heat-assisted magnetic head 380. FIG. 7 is a perspective view showing the laser diode 130. FIG. 8 is a perspective view showing the laser diode 130 to clarify the stripe-shaped p-electrode 142 and the stripe-shaped region 161M of the active layer 145 of the laser diode 130. FIG. 9 is a perspective view showing the light generating layer 150 included in the laser diode 130. FIG. 10 is a perspective view showing the active layer 145 included in the light generating layer 150. FIG. 11 is a perspective view showing the active layer 145 as viewed from the quantum dot layer 161. FIG. 12 is a cross-sectional view taken along the line 12-12 of FIG. 10 . FIG. 13 is a cross-sectional view taken along the line 13-13 of FIG. 10 .

[0109] As shown in FIG. 6 , the light source unit 360 includes the laser diode 130 and the base 350. The laser diode 130 is joined to the base 350 to constitute the light source unit 360.

[0110] The laser diode 130 is joined to the base 350 with a joining metal described later. Further, the laser diode 130 is joined to the base 350 so that the stripe-shaped p-electrode 142 described later opposes the surface insulating layer 350a (joining surface 351) of the base 350 described later. Thus, a joining metal layer 151 (joining surface 351) is formed between the stripe-shaped p-electrode 142 and the surface insulating layer 350a.

[0111] As shown in FIG. 6 , FIG. 7 , the laser diode 130 has an n-substrate 140, an n-electrode 141, a light generating layer 150, insulating layers 148a, 148b, a p-cladding layer 149, and a stripe-shaped p-electrode 142 having a straight strip shape.

[0112] The stripe-shaped n-electrode 141 is joined to a surface outside the n-substrate 140. Further, the light generating layer 150 is formed on the side of the n-substrate 140 opposite the stripe-shaped n-electrode 141, and the insulating layers 148a, 148b and the p-cladding layer 149 are formed on the light generating layer 150. Further, the stripe-shaped p-electrode 142 is formed on a surface outside the p-cladding layer 149. The p-cladding layer 149 is a portion having a straight strip shape, and is also referred to as “stripe-shaped”. The p-cladding layer 149 restricts the direction of injected current and the movement of electrons and holes inside the laser diode 130.

[0113] As FIG. 7 , FIG. 9 illustrated in detail, the light generating layer 150 includes the active layer 145 as a pn junction layer, the n-clad layer 147, and the p-clad layer 146. The light generating layer 150 has a structure in which the active layer 145 is sandwiched between the n-clad layer 147 and the p-clad layer 146.

[0114] Then, as FIG. 4 illustrated, the laser diode 130 is bonded to the base 350 so that the active layer 145 is opposed to the core layer 25, and a laser emission portion 145A (see FIG. 7 ) of the active layer 145 is disposed in a portion opposed to the core layer 25.

[0115] As described later, as FIG. 10 illustrated, in the heat-assisted magnetic head 380, since the active layer 145 includes five quantum dot layers 161 to 165, the five quantum dot layers 161 to 165 constituting the active layer 145 are opposed to the core layer 25. Note that the laser emission portion 145A is a portion in the laser diode 130 from which a laser beam is emitted.

[0116] The base 350 is made of, for example, silicon (Si), and is formed in a cuboid shape. As FIG. 1 , FIG. 6 illustrated, the size of the base 350 is larger than the size of the laser diode 130. Further, the base 350 can be formed of a semiconductor material such as GaAs, SiC, or the like, or a ceramic material such as aluminum oxide-titanium carbide (Al2O3·TiC), or the like.

[0117] Then, as FIG. 6 illustrated in detail, the base 350 has a surface insulating layer 350a made of silicon dioxide (SiO2). A surface of the surface insulating layer 350a constitutes a bonding surface 351 to which the laser diode 130 is bonded. The bonding surface 351 is formed in a flat rectangular shape. The size of the bonding surface 351 is larger than the size of the laser diode 130.

[0118] (active layer)

[0119] Next, the active layer 145 will be described with reference to FIGS. 6-8 , in addition to FIGS. 10-13 .

[0120] As FIG. 10As shown, the active layer 145 includes five quantum dot layers 161, 162, 163, 164, 165. The active layer 145 has a multilayer structure in which the five quantum dot layers 161 to 165 are stacked. Among the quantum dot layers 161 to 165, the quantum dot layer 161 is arranged closest to the strip-shaped p-electrode 142, and the quantum dot layer 165 is arranged closest to the n-electrode 141.

[0121] As shown, a plurality of quantum dots 166 are formed in the respective quantum dot layers 161 to 165. The respective quantum dots 166 are particles made of a semiconductor, and have a size of about several nm (nanometers). In the active layer 145, a carrier (an electron or a positive hole) is confined in a minute region of the quantum dot 166. The movement of the carrier is restricted in three-dimensional directions by the respective quantum dots 166. FIGS. 11-13 As shown, the quantum dot layers 161 to 165 include strip-shaped regions 161M, 162M, 163M, 164M, 165M, respectively. The strip-shaped regions 161M to 165M are regions each having a band shape, and are arranged around the center of the respective quantum dot layers 161 to 165.

[0122] FIG. 11 , FIG. 13 As shown, the strip-shaped regions 161M to 165M are formed in the respective quantum dot layers 161 to 165 at positions corresponding to the strip-shaped p-electrode 142. In

[0123] In the band shape shown in FIG. 1, the portions shown as dots correspond to the strip-shaped regions 161M to 165M. FIG. 8 FIG. 8 As shown, in addition to the strip-shaped regions 161M, 162M, 163M, 164M, 165M, an outer region (a region other than the strip-shaped regions 161M, 162M, 163M, 164M, 165M) is a side surface region 161A, 162A, 163A, 164A, 165A in the respective quantum dot layers 161, 162, 163, 164, 165.

[0124] As shown, the strip-shaped regions 161M to 165M are formed in the respective quantum dot layers 161 to 165 at positions corresponding to the strip-shaped p-electrode 142. In FIG. 11 FIG. 12 ,

[0125] As shown, the strip-shaped regions 161M to 165M are formed in the respective quantum dot layers 161 to 165 at positions corresponding to the strip-shaped p-electrode 142. In FIG. 11 FIG. 13 ​​​​As shown, window regions 161Ma, 161Mb, 162Ma, 162Mb, 163Ma, 163Mb, 164Ma, 164Mb, 165Ma, and 165Mb are formed in the corresponding strip regions 161M, 162M, 163M, 164Mb, 165Ma, and 165Mb. The window regions 161Ma, 161Mb to 165Ma, and 165Mb are the regions corresponding to the laser emitting section 145A and the back surface regions of the corresponding strip regions 161M to 165M (for example, ...). FIG. 11 (The rectangular area shown). Because window areas 161Ma to 165Ma are the areas corresponding to the laser emitting unit 145A (front facet), the laser beam is emitted from window areas 161Ma to 165Ma. Window areas 161Mb to 165Mb are the areas arranged on the back side of window areas 161Ma to 165Ma (rear facet), and they are not areas where the laser beam is emitted.

[0126] In the active layer 145, quantum dot layers 161 to 165 respectively include window regions 161Mb, 161Mb to 165Mb, and 165Mb. Therefore, according to the present invention, quantum dot layers 161 to 165 correspond to window-formed quantum dot layers. The active layer 145 has a multilayer structure formed by stacking window-formed quantum dot layers.

[0127] Then, in the active layer 145, within the corresponding quantum dot layers 161 to 165, the corresponding window regions 161Ma, 161Mb to 165Ma, and 165Mb are low-density regions. Low-density regions refer to areas where the arrangement density of quantum dots 166 is lower than in other regions. Regarding the arrangement density of quantum dots 166, the corresponding window regions 161Ma, 161Mb to 165Ma, and 165Mb are smaller than the regions other than these window regions. The arrangement density of quantum dots 166 can be determined based on the number of quantum dots 166 arranged per unit area.

[0128] like FIGS. 11-13 As shown, in the side regions 161A to 165A and the middle regions 161Md, 162Md, 163Md, 164Md, and 165Md of the strip-shaped regions 161M to 165M, a large number of quantum dots 166 are arranged and densely packed, except for the window regions 161Ma, 161Mb to 165Ma, and 165Mb. These regions are crowded regions CR. On the other hand, in the window regions 161Ma, 161Mb to 165Ma, and 165Mb, the quantum dots 166 are discretely arranged. Therefore, the window regions 161Ma, 161Mb to 165Ma, and 165Mb are discrete regions SR.

[0129] For reference here FIG. 6 ,FIG. 7 The bonding metal layer 151 is formed of a bonding metal. The bonding metal is a metal used to bond the laser diode 130 and the mount 350. In the case of the light source unit 360, for example, a solder (an alloy metal including tin), tin (Sn), and gold (Au) can be used as the bonding metal. When tin (Sn) and gold (Au) are used as the bonding metal, an alloy layer made of an alloy including tin and gold (an AuSn alloy) and a metal layer including gold are included in the bonding metal layer 151.

[0130] (Operation and effects of the light source unit)

[0131] As described above, as shown in FIG. 1, the laser diode 130 is bonded to the mount 350, thereby manufacturing the light source unit 360. As shown in FIG. 2, the active layer 145 of the laser diode 130 includes five quantum dot layers 161 to 165, and as shown in FIG. 3, a plurality of quantum dots 166 are formed in the respective quantum dot layers 161 to 165. FIG. 6 FIG. 10 FIG. 11 The quantum dots 166 are semiconductor particles that restrict the movement of carriers (electrons or positive holes) in three-dimensional directions.

[0132] Generally, a structure that restricts a carrier in an extremely narrow region is called a quantum well (QW). In a quantum well, the movement of a carrier is restricted in one-dimensional directions. In this case, the quantum well is constituted of a planar thin film made of a semiconductor having an extremely thin thickness.

[0133] Incidentally, generally, when an active layer is changed from a bulk semiconductor to a quantum well, the state density indicating the number of seats of carriers changes. In a bulk semiconductor, the state density shows a continuous parabolic shape, whereas in a quantum well, the state density shows a stair-like shape. The peak of the emission wavelength occurs at the stair of the stair-like shape, and the width of the emission wavelength narrows. This is a characteristic in the case where the active layer is a quantum well.

[0134] Then, according to the embodiment, the active layer 145 of the light source unit 360 includes the quantum dot layers 161 to 165. The quantum dots 166 of the respective quantum dot layers 161 to 165 restrict the movement of carriers in three-dimensional directions. In the case of a quantum well, the dimension of quantization is one-dimensional, but in the case of the active layer 145, because the quantum dots 166 are formed in the respective quantum dot layers 161 to 165, the dimension of quantization evolves into three-dimensional.

[0135] Then, because the dimension of quantization evolves from one-dimensional to three-dimensional, in the active layer 145, the state density is more discrete than in the case of a quantum well in one-dimensional. That is, in the active layer 145, because the quantum dots 166 are included, the existence of carriers is concentrated in a specific energy state. ​​

[0136] On the other hand, the Fermi distribution function showing the energy distribution of electrons has a temperature dependency, and the distribution of carriers varies depending on the temperature. Therefore, the characteristics of the laser diode vary depending on the temperature.

[0137] However, in the case of the laser diode 130, since the dimension of quantization evolves from one dimension to three dimensions, in the active layer 145, the state density is discretized, and thereby the existence of carriers is concentrated in a specific energy state. Thereby, even if the Fermi distribution function varies depending on the change in temperature, the state density as a seat of carriers is fixed at a specific energy position.

[0138] Therefore, in the case where the laser diode 130 includes the quantum dots 166, even if the temperature varies, the effective carrier distribution hardly varies.

[0139] Thereby, in the case of the laser diode 130, since the variation in characteristics hardly varies depending on the change in temperature, the temperature characteristics of the laser diode 130 are greatly improved.

[0140] As described above, the active layer 145 includes the quantum dot layers 161 to 165 in which the quantum dots 166 are respectively formed, and thereby the laser diode 130 is designed to be insensitive to temperature.

[0141] Therefore, since heat is generated depending on the data recording operation of the write head 91 and heat is generated depending on the light emission of the laser diode 130, even if the heat-assisted magnetic head 380 including the laser diode 130 is placed in an environment in which a temperature change easily occurs, it is difficult for the mode hopping of the laser diode 130 to occur. Therefore, the recording quality of the heat-assisted magnetic head 380 does not deteriorate, and the recording quality is stable.

[0142] On the other hand, since the quantum dots 166 are each a minute semiconductor particle, the intensity of the laser beam obtained from the corresponding quantum dot 166 is very small.

[0143] However, in the laser diode 130, a large number of quantum dots 166 are formed by the multilayer structure including the quantum dot layers 161 to 165. Thereby, the light emission intensity of the laser beam in the light source unit 360 is improved.

[0144] Further, the corresponding quantum dot layers 161 to 165 include stripe regions 161M to 165M depending on the stripe p-electrode 142 in the light source unit 360. Therefore, the particle distribution inversion necessary for stimulated emission is formed along the stripe regions 161M to 165M, and thereby the laser beam is guided along the stripe regions 161M to 165M.

[0145] Then, in the light source unit 360, since the low-density regions are formed in the respective stripe regions 161M to 165M, the arrangement density of the quantum dots 166 is partially reduced in the respective stripe regions 161M to 165M. Then, the movement of the carriers is restricted between the stripe p-electrode 142 and the n-electrode 141, and the absorption of the laser beam is reduced in the stripe regions 161M to 165M.

[0146] Further, the low-density regions are formed in the window regions 161Ma, 161Mb to 165Ma, 165Mb of the stripe regions 161M to 165M. Therefore, when the laser beam generated in the stripe regions 161M to 165M is emitted from the laser emission part 145A, the absorption of the laser beam is also reduced. Therefore, the thermal effect at the resonator end face is reduced, and thus the operating life of the laser, particularly at the end face, is improved.

[0147] Further, the light source unit 360 has a multilayer structure in which the quantum dot layers 161 to 165, which are formed as windows, are stacked. Therefore, in the light source unit 360, both the light emission intensity of the laser beam is improved by the multilayer structure and the absorption of the laser beam is reduced by the structure of the windows. Therefore, the thermal effect at the resonator end face is reduced, and thus the operating life of the laser, particularly at the end face, is improved.

[0148] (First modification example)

[0149] Next, a heat-assisted magnetic head and a light source unit according to the first modification example will be described with reference to FIGS. 14-18 the drawings. The heat-assisted magnetic head and the light source unit according to the first modification example are different from the heat-assisted magnetic head 380 and the light source unit 360 described above in the active layer of the laser diode 130, respectively. That is, in the case of the heat-assisted magnetic head 380 and the light source unit 360 described above, the laser diode 130 includes the active layer 145. On the other hand, in the case of the heat-assisted magnetic head and the light source unit according to the first modification example, the laser diode includes the active layer 245, as FIGS. 14-17 shown in FIG. 2.

[0150] The active layer 145 includes five quantum dot layers 161, 162, 163, 164, 165. In contrast, the active layer 245 includes five quantum dot layers 171, 172, 173, 174, 175. Like the active layer 145, the active layer 245 has a multilayer structure in which the five quantum dot layers 171 to 175 are stacked.

[0151] Further, as FIGS. 15-18 shown in FIG. 2, like the quantum dot layers 161 to 165, a plurality of quantum dots 166 are formed in the respective quantum dot layers 171 to 175.

[0152] However, compared to quantum dot layers 161 to 165, quantum dot layers 171 to 175 differ in the distribution of multiple quantum dots 166.

[0153] like FIG. 15 As shown, in the case of active layer 245, quantum dot layers 171, 173, and 175 are even-numbered dot layers, while quantum dot layers 172 and 174 are odd-numbered dot layers. That is, multiple quantum dots 166 are uniformly formed in almost all of the corresponding quantum dot layers 171, 173, and 175. Conversely, quantum dot layers 172 and 174 each include dotless regions in which no quantum dots 166 are formed. FIG. 18 (The area indicated by "nQD" in the text).

[0154] Then, as FIG. 15 As shown, in the case of active layer 245, quantum dot layers 171, 173, and 175, which are even-numbered dot layers, and quantum dot layers 172 and 174, which are odd-numbered dot layers, are stacked alternately.

[0155] like FIGS. 15-17 As shown, quantum dot layers 171, 173, and 175 include strip-shaped regions 171M, 173M, and 175M, and side regions 171A, 173A, and 175A, respectively. Furthermore, quantum dot layers 171, 173, and 175 include window regions 171m, 171n, 173m, 173n, 175m, and 175n, respectively.

[0156] In the case of the active layer 145 described above, the window regions 161Ma, 161Mb to 165Ma, 165Mb are discrete regions SR. However, in the case of quantum dot layers 171, 173, and 175, all the strip regions 171M, 173M, 175M, the side regions 171A, 173A, 175A, and the window regions 171m, 171n, 173m, 173n, 175m, 175n are crowded regions CR. Note that the window regions 171m, 171n, 173m, 173n, 175m, 175n are the regions of the corresponding quantum dot layers 171, 173, and 175 corresponding to the laser emitting section 145A and the back surface region ( FIG. 17 The window areas 171m and 171n are shown in the figure.

[0157] like FIG. 15 , FIG. 16 , FIG. 18 As shown, quantum dot layers 172 and 174 include strip regions 172M and 174M and side regions 172A and 174A, respectively. In addition, quantum dot layers 172 and 174 include window regions 172m, 172n, 174m, and 174n, respectively.

[0158] Then, the active layer 145 includes the window regions 161Ma, 161Mb to 165Ma, 165Mb as low-density regions as discrete regions SR.

[0159] However, the active layer 245 includes the window regions 172m, 172n, 174m, 174n as low-density regions as point-free regions nQD. The window regions 172m, 172n, 174m, 174n are point-free regions nQD because they do not include quantum dots 166, but they are low-density regions because the arrangement density of the quantum dots 166 is less than that of the other regions.

[0160] As described above, like the active layer 145, the active layer 245 includes a plurality of quantum dots 166. Therefore, like the laser diode 130 including the active layer 145, a laser diode (not shown) including the active layer 245 is designed to be insensitive to temperature. Therefore, like the thermal-assisted magnetic head 380 including the active layer 145, in the case of a thermal-assisted magnetic head including the active layer 245, the recording quality is also stable without being degraded.

[0161] Further, like the active layer 145, the active layer 245 includes a multilayer structure formed by the quantum dot layers 171 to 175. Therefore, the emission intensity of a laser beam in a light source unit including the active layer 245 is improved.

[0162] Further, as FIGS. 19-23 indicated, like the active layer 145, the active layer 245 includes the stripe regions 171M to 175M, and a part (the window regions 172m, 172n, 174m, 174n) of the stripe regions 172M, 174M is a point-free region nQD. Therefore, the movement of carriers is restricted between the stripe p-electrode 142 and the n-electrode 141, and the absorption of a generated laser beam is reduced in the stripe regions 172M, 174M. Therefore, a laser beam is effectively generated in the active layer 245 as a whole. As a result, the power consumption in a light source unit including the active layer 245 is reduced.

[0163] Further, since the window regions 172m, 172n, 174m, 174n are point-free regions nQD, the absorption of a laser beam is reduced in the window regions 172m, 172n, 174m, 174n. Therefore, when a laser beam is emitted from the laser emission part 145A of the active layer 245, the absorption of the laser beam is also reduced. Therefore, the thermal effect at the resonator end face is reduced, and thus the operating life of the laser, particularly at the end face, is improved.

[0164] (Second Modification Example)

[0165] Next, a description will be given of a second modification example of the active layer 245. FIGS. 19-23This section describes the heat-assisted magnetic head and light source unit according to the second modified example. Compared to the heat-assisted magnetic head 380 and light source unit 360 described above, the heat-assisted magnetic head and light source unit according to the second modified example differ in the active layer of the laser diode 130. That is, in the case of the heat-assisted magnetic head 380 and light source unit 360 described above, the laser diode 130 includes an active layer 145. On the other hand, according to the second modified example, in the case of the heat-assisted magnetic head and light source unit, the laser diode includes an active layer 255, such as... FIGS. 20-23 As shown.

[0166] The active layer 145 comprises five quantum dot layers 161 to 165. Conversely, the active layer 255 comprises five quantum dot layers 181, 182, 183, 184, and 185. Similar to the active layer 145, the active layer 255 has a multilayer structure formed by stacking five quantum dot layers 181 to 185.

[0167] In addition, such as FIG. 22 As shown, similar to quantum dot layers 161 to 165, multiple quantum dots 166 are formed in the corresponding quantum dot layers 181 to 185.

[0168] However, compared to quantum dot layers 161 to 165, quantum dot layers 181 to 185 differ in the distribution of multiple quantum dots 166.

[0169] like FIG. 21 As shown, in the case of active layer 255, quantum dot layers 181 and 185 are even-numbered dot layers, while quantum dot layers 182, 183, and 184 are odd-numbered dot layers. That is, multiple quantum dots 166 are formed in almost the entirety of the corresponding quantum dot layers 181 and 185. Conversely, quantum dot layers 182, 183, and 184 each include dotless regions where no quantum dots 166 are formed. FIG. 20 (The area indicated by "nQD" in the text).

[0170] Then, in the case of active layer 255, quantum dot layers 181 and 185, which are even-numbered dot layers, are stacked to sandwich quantum dot layers 182 to 184, which are odd-numbered dot layers.

[0171] like FIG. 22 , FIG. 22 As shown, quantum dot layers 181, 182, 183, 184, and 185 respectively include strip-shaped regions 181M, 182M, 183M, 184M, and 185M and side regions 181A, 182A, 183A, 184A, and 185A. Furthermore, the strip-shaped regions 181M, 182M, 183M, 184M, and 185M respectively include central regions 181Mm, 182Mm, 183Mm, 184Mm, and 185Mm, and the central regions 182Mm, 183Mm, and 184Mm are formed within the dotless region nQD.

[0172] Then, the active layer 145 includes window regions 161Ma, 161Mb to 165Ma, 165Mb, which are discrete regions SR.

[0173] However, in the case of quantum dot layers 181 and 185, all regions, including the strip regions 181M and 185M and the side regions 181A and 185A, are crowded regions CR. In the case of quantum dot layers 181 and 185, all regions are crowded regions CR. Furthermore, in the case of quantum dot layers 182, 183, and 184, central regions 182Mm, 183Mm, and 184Mm are formed in the dotless region nQD.

[0174] Then, in the case of the active layer 145, the five quantum dot layers 161 to 165 respectively include window regions 161Ma, 161Mb to 165Ma, and 165Mb as low-density regions, which are discrete regions SR.

[0175] On the contrary, such as FIG. 21 As shown, in the case of active layer 255, quantum dot layers 182, 183, and 184 of the five quantum dot layers 181 to 185 include the central regions 182Mm, 183Mm, and 184Mm as low-density regions, which serve as the pointless region nQD.

[0176] As described above, similar to active layer 145, active layer 255 includes a plurality of quantum dots 166. Therefore, similar to laser diode 130 including active layer 145, laser diode (not shown) including active layer 255 is designed to be temperature insensitive. Therefore, similar to heat-assisted magnetic head 380 including active layer 145, in the case of heat-assisted magnetic head including active layer 255, recording quality is also stable without degradation.

[0177] Furthermore, similar to the active layer 145, the active layer 255 comprises a multilayer structure formed by quantum dot layers 181 to 185. Therefore, the luminous intensity of the laser beam in the light source unit including the active layer 255 is increased.

[0178] In addition, such as FIGS. 24-27 As shown, similar to the active layer 145, the active layer 255 includes strip-shaped regions 181M to 185M, a portion of which is a pointless region nQD. Therefore, carrier movement is confined between the strip-shaped p-electrode 142 and the n-electrode 141, reducing laser beam absorption in the strip-shaped regions 182M to 184M. Thus, the laser can control the shape of the laser beam by controlling the size and area of ​​the pointless region nQD.

[0179] (Third Modification Example)

[0180] Next, a heat-assisted magnetic head and a light source unit according to a third modification example will be described with reference to FIGS. 24-27 FIG. 17. Compared with the heat-assisted magnetic head 380 and the light source unit 360 described above, the heat-assisted magnetic head and the light source unit according to the third modification example differ in the active layer of the laser diode 130, respectively. That is, in the case of the heat-assisted magnetic head 380 and the light source unit 360 described above, the laser diode 130 includes the active layer 145. On the other hand, according to the third modification example, in the case of the heat-assisted magnetic head and the light source unit, the laser diode includes the active layer 265, as FIGS. 25-27 shown in FIG. 17.

[0181] The active layer 145 described above includes five quantum dot layers 161 to 165. In contrast, the active layer 265 includes five quantum dot layers 191, 192, 193, 194, 195. Like the active layer 145, the active layer 265 has a multilayer structure in which the five quantum dot layers 191 to 195 are stacked.

[0182] Further, as FIG. 25 shown in FIG. 17, like the quantum dot layers 161 to 165, a plurality of quantum dots 166 are formed in the respective quantum dot layers 191 to 195. Further, the quantum dot layers 191 to 195 include window regions 191Ma, 191Mb to 195Ma, 195Mb in which quantum dots 167 described later are formed.

[0183] As FIG. 26 , FIG. 25 shown in FIG. 17, the quantum dot layers 191 to 195 respectively include strip regions 191M, 192M, 193M, 194M, 195M and side regions 191A, 192A, 193A, 194A, 195A.

[0184] Then, as FIG. 26 , FIG. 25 shown in FIG. 17, the window regions 191Ma, 191Mb, 192Ma, 192Mb, 193Ma, 193Mb, 194Ma, 194Mb, 195Ma, 195Mb are formed in the respective strip regions 191M, 192M, 193M, 194M, 195M.

[0185] The quantum dots 167 are discretely arranged in the respective window regions 191Ma, 191Mb to 195Ma, 195Mb. Like the window regions 161Ma, 161Mb to 165Ma, 165Mb, the respective window regions 191Ma, 191Mb to 195Ma, 195Mb are discrete regions SR, and they are low-density regions, respectively.

[0186] The quantum dots 167 have a larger size than the quantum dots 166. Further, instead of the quantum dots 167, the quantum dots 168 described later can be formed in the respective window regions 191Ma, 191Mb to 195Ma, 195Mb.

[0187] Because the quantum dots 167 have a size larger than the quantum dots 166, the respective quantum dot layers 191 to 195 have structures with different sizes.

[0188] As described above, like the active layer 145, the active layer 265 includes a plurality of quantum dots 166. Therefore, like the laser diode 130 including the active layer 145, the laser diode (not shown) including the active layer 265 is designed to be insensitive to temperature. Therefore, like the thermal assist head 380 including the active layer 145, in the case of the thermal assist head including the active layer 265, the recording quality is also stable without being degraded.

[0189] Further, like the active layer 145, the active layer 265 includes a multilayer structure formed of the quantum dot layers 191 to 195. Therefore, the emission intensity of the laser beam in the light source unit including the active layer 265 is improved.

[0190] In the stripe regions 191M to 195M, because a part (the window regions 191Ma, 191Mb to 195Ma, 195Mb) of the stripe regions 191M to 195M is a low-density region, the absorption of the laser beam is reduced. Therefore, the thermal effect at the resonator end face is reduced, thereby improving the service life of the laser, particularly at the end face.

[0191] Further, the low-density regions are formed in the window regions 191Ma, 191Mb to 195Ma, 195Mb of the stripe regions 191M to 195M. Therefore, when the laser beam generated within the stripe regions 191M to 195M is emitted from the laser emission portion 145A, the absorption of the laser beam is also reduced.

[0192] Further, because the size of the quantum dots 167 formed in the window regions 191Ma, 191Mb to 195Ma, 195Mb is larger than the size of the quantum dots 166, the band gap energy is larger. Therefore, the absorption of the laser beam generated within the active layer 265 is reduced in the window regions 191Ma, 191Mb to 195Ma, 195Mb, thereby prolonging the service life of the laser diode.

[0193] On the other hand, the quantum dots 168 differ in composition from the quantum dots 166, respectively. When the quantum dots 168 are formed in the window regions 191Ma, 191Mb to 195Ma, 195Mb, the quantum dot layers 191 to 195 have structures with different compositions, respectively.

[0194] For example, when the quantum dot 166 is composed of In 0.5 Ga 0.5 N, the quantum dot 168 can be composed of In 0.4 Ga 0.6 N. In this case, similar operation and effects to those in the case where the quantum dot 167 is formed in the window regions 191Ma, 191Mb to 195Ma, 195Mb can be obtained. As FIG. 28 indicated, note that the quantum dot 168 can have the same size as the quantum dot 167, and the quantum dot 168 can have the same size as the quantum dot 166.

[0195] (Fourth Modification Example)

[0196] Next, a heat-assisted magnetic head and a light source unit according to the fourth modification example will be described with reference to FIG. 28 Fig. 23. The heat-assisted magnetic head and the light source unit according to the fourth modification example differ from the heat-assisted magnetic head 380 and the light source unit 360 described above in the active layer of the laser diode 130. That is, in the case of the heat-assisted magnetic head 380 and the light source unit 360 described above, the laser diode 130 includes the active layer 145. On the other hand, according to the fourth modification example, in the case of the heat-assisted magnetic head and the light source unit, the laser diode includes an active layer 275, as FIG. 28 indicated in Fig. 23.

[0197] The active layer 275 includes five quantum dot layers 201, 202, 203, 204, 205. Like the active layer 145, the active layer 275 has a multilayer structure in which the five quantum dot layers 201 to 205 are stacked.

[0198] Further, like the quantum dot layers 161 to 165, as FIG. 28 indicated in Fig. 23, a plurality of quantum dots 166 are formed in the respective quantum dot layers 201 to 205.

[0199] Further, like the quantum dot layers 161 to 165, the quantum dot layers 201 to 205 respectively include strip regions 201M, 202M, 203M, 204M, 205M and side regions 201A, 202A, 203A, 204A, 205A.

[0200] Then, window regions 201E, 201F, 202E, 202F, 203E, 203F, 204E, 204, 205E, 205F (exemplification of the window regions 202E to 205E, 202F to 205F is omitted) are formed in the respective strip regions 201M, 202M, 203M, 204M, 205M. Further, the window regions 201E, 201F to 205E, 205F are low-density regions.

[0201] In the case of the window regions 201E, 201F to 205E, 205F, as shown in FIG. 29 the length in the direction of the end surface of the active layer 275 is longer than the stripe regions 201M to 205M. Therefore, the absorption of the laser beam is reduced in the window regions 201E, 201F to 205E, 205F compared to the active layer 145. Therefore, the power consumption is reduced in the case of the light source unit including the active layer 275 compared to the light source unit 360 including the active layer 145. Therefore, the thermal effect at the end surface of the resonator is reduced, thereby improving the operating life of the laser, particularly at the end surface. Further, similar operation and effects to the light source unit 360 including the active layer 145 can be obtained in the case of the light source unit including the active layer 275.

[0202] (Fifth Modified Example)

[0203] Next, the heat-assisted magnetic head and the light source unit according to the fifth modified example will be described with reference to FIG. 29 Compared to the heat-assisted magnetic head 380, the light source unit 360 described above, the heat-assisted magnetic head and the light source unit according to the fifth modified example differ in the active layer of the laser diode 130. That is, in the case of the heat-assisted magnetic head 380, the light source unit 360 described above, the laser diode 130 includes the active layer 145. On the other hand, according to the fifth modified example, in the case of the heat-assisted magnetic head, the light source unit, the laser diode includes the active layer 285, as shown in FIG. 29 .

[0204] The active layer 285 includes five quantum dot layers 211, 212, 213, 214, 215. Like the active layer 145, the active layer 285 has a multilayer structure in which the five quantum dot layers 211 to 215 are stacked.

[0205] Further, like the quantum dot layers 161 to 165, as shown in FIG. 29 , a plurality of quantum dots 166 are formed in the respective quantum dot layers 211 to 215.

[0206] Further, like the quantum dot layers 161 to 165, the quantum dot layers 211 to 215 respectively include stripe regions 211M, 212M, 213M, 214M, 215M and side surface regions 211A, 212A, 213A, 214A, 215A.

[0207] Then, window regions 211G, 211H, 212G, 212H, 213G, 213H, 214G, 214H, 215G, 215H (exemplification of the window regions 212G to 215G, 212H to 215H is omitted) are formed in the strip regions 211M, 212M, 213M, 214M, 215M, respectively. Further, the window regions 211G, 211H to 215G, 215H are low-density regions.

[0208] In the case of the window regions 211G, 211H to 215G, 215H, as shown in FIGS. 30-31 the length in the direction of the end surface of the active layer 285 is longer than the strip regions 211M to 215M. Therefore, the absorption of the laser beam is reduced in the window regions 211G, 211H to 215G, 215H compared to the active layer 145. Therefore, the power consumption is reduced in the case of the light source unit including the active layer 285 compared to the light source unit 360 including the active layer 145. Therefore, the thermal effect at the end surface of the resonator is reduced, thereby improving the operating life of the laser, particularly at the end surface. Further, in the case of the light source unit including the active layer 285, similar operation and effects to the light source unit 360 including the active layer 145 can be obtained.

[0209] (Embodiments of head gimbal assembly and hard disk drive)

[0210] Next, embodiments of the head gimbal assembly and hard disk drive will now be described with reference to FIG. 30

[0211] FIG. 31 is a perspective view showing a hard disk drive 401 equipped with the above-described thermal assist head 380. The hard disk drive 401 includes a hard disk (magnetic recording medium) 402 that rotates at high speed and a head gimbal assembly (HGA) 410. The hard disk drive 401 is a device that actuates the HGA 410 to record data on a recording surface of the hard disk 402 / reproduce data from the recording surface of the hard disk. The hard disk 402 has a plurality of (4 in the figure) disks. Each disk has a recording surface opposite to the thermal assist head 380 corresponding thereto.

[0212] The hard disk drive 401 positions the slider 120 on the track by an assembly holder device 403. Further, the hard disk drive 401 has a plurality of drive arms 409. The drive arms are pivoted about a pivot support shaft 406 by means of a voice coil motor (VCM) 205 and stacked in the direction of the pivot support shaft 406. In addition, the HGA 410 is attached to the tip end of each drive arm.

[0213] ​Further, the hard disk drive 401 has a control circuit 404 that controls recording / reproduction of the laser diode 130 and generation of light.

[0214] ​ FIG. 13 is a perspective view showing the rear surface side of the HGA 410. In the HGA 410, the heat-assisted magnetic head 380 is fixed to the tip end portion of the suspension 420. Further, in the HGA 410, one end portion of the wiring member 424 is electrically connected to the terminal electrode of the slider 120.

[0215] The suspension 420 has a load beam 422, a base plate 421 provided at the base of the load beam 422, a flexure 423 fixed and supported on the load beam 422 from the tip end side to the front side of the base plate 421 and having elasticity, and a wiring member 424. The wiring member 424 has a lead conductor and connection pads electrically connected to both ends of the lead conductor.

[0216] In the hard disk drive 401, when the HGA 410 rotates, the slider 120 moves in the radial direction of the hard disk 402, that is, in a direction transverse to the track line.

[0217] Because the aforementioned HGA 410 and hard disk drive 401 have the heat-assisted magnetic head 380, the laser diode 130 of the light source unit 360 is designed to be temperature-insensitive, so that the recording quality of the heat-assisted magnetic head 380 is stable.

[0218] Although the above-described embodiment illustrates a type in which the thin film coil is wound like a flat spiral on the main pole layer by way of example, the present application is also applicable to a type in which the thin film coil is spirally wound on the main pole layer. Further, in the above-described embodiment, although a case in which the active layer includes five quantum dot layers is illustratively described as the active layer 145, it is preferable that the active layer include at least two quantum dot layers.

[0219] The present application is not limited to the foregoing embodiments, but various changes and modifications can be made to the components thereof without departing from the scope of the present application. Further, it is obvious that various embodiments and modified examples of the present application can be implemented based on the foregoing description. Therefore, the present application can be implemented in other modes than the above-described best modes within the scope equivalent to the appended claims.

Claims

1. A light source unit for a heat-assisted magnetic head, comprising: a laser diode; and a base to which the laser diode is joined; wherein the laser diode includes a light generating layer including an active layer that emits laser light and a cladding layer formed to sandwich the active layer, wherein the active layer includes a quantum dot layer including a plurality of quantum dots having a property of restricting movement of a carrier in three-dimensional directions; wherein the active layer includes at least two quantum dot layers, wherein the active layer includes a multilayer structure of the at least two quantum dot layers stacked, wherein the multilayer structure is a structure of an even-numbered quantum dot layer and an odd-numbered quantum dot layer alternately stacked, the even-numbered quantum dot layer including the quantum dots formed in almost the entire corresponding quantum dot layer, and the odd-numbered quantum dot layer including a no-dot region in which the quantum dots are not formed.

2. The light source unit according to claim 1, wherein, wherein the quantum dot layer includes a low-density region of which arrangement density of the quantum dots is lower than that of other regions.

3. The light source unit according to claim 1, wherein wherein the laser diode includes a strip-shaped electrode formed in a straight strip shape, wherein the quantum dot layer includes a low-density region of which arrangement density of the quantum dots is lower than that of other regions, the low-density region being arranged in a strip-shaped region corresponding to the strip-shaped electrode.

4. The light source unit according to claim 3, wherein wherein the low-density region is arranged in a window region of the strip-shaped region, the window region corresponding to both end portions of a laser resonator.

5. The light source unit according to claim 1, wherein wherein the laser diode includes a strip-shaped electrode formed in a straight strip shape, wherein the multilayer structure is a structure of window-formed quantum dot layers stacked as the quantum dot layers, the window-formed quantum dot layer including a low-density region of which arrangement density of the quantum dots is lower than that of other regions, the low-density region being arranged in a window region of a strip-shaped region, the strip-shaped region corresponding to the strip-shaped electrode, the window region corresponding to both end portions of a laser resonator.

6. The light source unit according to claim 1, wherein wherein in the corresponding odd-numbered quantum dot layer, the no-dot region is arranged in a window region corresponding to both end portions of a laser resonator.

7. A light source unit for a heat-assisted magnetic head, comprising: a laser diode; and a base to which the laser diode is joined; wherein the laser diode includes a light generating layer including an active layer that emits laser light and a cladding layer formed to sandwich the active layer, wherein the active layer includes a quantum dot layer including a plurality of quantum dots having a property of restricting movement of a carrier in three-dimensional directions; wherein the active layer includes at least two quantum dot layers, wherein the active layer includes a multilayer structure of the at least two quantum dot layers stacked, wherein the multilayer structure is a structure in which an even-numbered dot layer and an odd-numbered dot layer are stacked so that the even-numbered dot layer sandwiches the odd-numbered dot layer, the even-numbered dot layer includes the quantum dots, the quantum dots are formed in almost the entire corresponding quantum dot layer, and the odd-numbered dot layer includes a dot-free region in which the quantum dots are not formed.

8. The light source unit according to claim 7, wherein, the dot-free region is arranged in a central region, the central region including a central portion of the odd-numbered dot layer.

9. The light source unit according to claim 4, wherein, the quantum dot layer includes structures of different sizes, the structures of different sizes having sizes of the quantum dots formed in the low-density region, the structures of different sizes having sizes larger than sizes of the quantum dots formed in a region other than the low-density region.

10. The light source unit according to claim 4, wherein the quantum dot layer includes structures of different compositions, the structures of different compositions having compositions of the quantum dots formed in the low-density region, the structures of different compositions having compositions different from compositions of the quantum dots formed in a region other than the low-density region.

11. The light source unit according to claim 4, wherein, in the corresponding quantum dot layer, the window region has a length longer than the strip region in a direction along an end surface of the active layer.

12. The light source unit according to claim 4, wherein in the corresponding quantum dot layer, the window region has a length longer than the strip region in a direction along an end surface of the active layer as the window region gradually approaches the end surface of the active layer.

13. A heat-assisted magnetic head, comprising: a slider; and the light source unit according to claim 1 or 7 is joined to the slider, wherein the slider includes a slider substrate and a head portion, the head portion being formed in the slider substrate, wherein the head portion includes a waveguide in which laser light emitted from the light source unit is irradiated, wherein the quantum dot layer is opposite to the waveguide.

14. The heat-assisted magnetic head according to claim 13, wherein the active layer includes a multilayer structure in which the quantum dot layers are stacked.

15. The heat-assisted magnetic head according to claim 13, wherein the quantum dot layer includes a low-density region, the low-density region of the quantum dot layer having a lower arrangement density than other regions.

16. The heat-assisted magnetic head according to claim 13, wherein, the laser diode includes a strip electrode formed in a straight strip shape, wherein the quantum dot layer includes a low-density region, the low-density region of the quantum dot layer having a lower arrangement density than other regions, the low-density region being arranged in a strip region corresponding to the strip electrode.

17. The heat-assisted magnetic head according to claim 16, wherein, the low-density region is arranged in a window region, the window region corresponding to both end portions of a laser resonator.

18. A head gimbal assembly including a heat-assisted magnetic head, wherein, the heat-assisted magnetic head includes: a slider; and The light source unit according to claim 1 or 7 is joined to the slider, wherein the slider includes a slider base material and a head portion, the head portion being formed in the slider base material, wherein the head portion includes a waveguide, laser light emitted from the light source unit being irradiated in the waveguide, wherein the quantum dot layer is opposed to the waveguide.

19. A hard disk drive comprising: A head gimbal assembly having a heat-assisted magnetic head; and a magnetic recording medium opposed to the heat-assisted magnetic head, wherein the heat-assisted magnetic head includes: a slider; and The light source unit according to claim 1 or 7 is joined to the slider, wherein the slider includes a slider base material and a head portion, the head portion being formed in the slider base material, wherein the head portion includes a waveguide, laser light emitted from the light source unit being irradiated in the waveguide, wherein the quantum dot layer is opposed to the waveguide.

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