JP2007257753A - Micro optical recording head and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact micro optical recording head for recording information at a high density and a small optical spot, and its manufacturing method: the micro optical recording device; an optical assist type magnetic recording head, its manufacturing method, and an optical assist type magnetic recording device. <P>SOLUTION: The micro optical recording head for using a light for recoding information in a recording medium includes a slider 11 relatively moved while floating on the recording medium. The slider 11 includes an optical waveguide constituted of a core 31, a subcore 32, and a clad 33, and a plasmon probe 30 disposed in its condensing part. When the core 31 of the optical waveguide is formed, a core layer is formed up to the middle part, the plasmon probe 30 is formed in a part near the center of the core 31 from above and, when the core layer is formed after a remaining core layer is formed, the thick plasmon probe 30 is buried in the optical waveguide. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a minute optical recording head and a manufacturing method thereof, for example, a minute optical recording head using light for information recording, a manufacturing method thereof, and a light-assisted magnetic recording head using a magnetic field and light for information recording. And its manufacturing method.

  In the magnetic recording method, when the recording density increases, the magnetic bit is significantly affected by the external temperature and the like. For this reason, a recording medium having a high coercive force is required. However, when such a recording medium is used, the magnetic field required for recording also increases. The upper limit of the magnetic field generated by the recording head is determined by the saturation magnetic flux density, but this value is approaching the material limit and cannot be expected to increase dramatically. Therefore, a method of guaranteeing the stability of the recorded magnetic bit by locally heating at the time of recording, causing magnetic softening, recording with a reduced coercive force, and then stopping the heating and naturally cooling Has been proposed. This method is called a heat-assisted magnetic recording method.

In the heat-assisted magnetic recording method, it is desirable to instantaneously heat the recording medium. Further, the heating mechanism and the recording medium are not allowed to contact each other. For this reason, heating is generally performed using absorption of light, and a method using light for heating is called a light assist method. When ultra-high-density recording is performed by the optical assist method, the required spot diameter is about 20 nm. However, since a normal optical system has a diffraction limit, the light cannot be condensed to that extent. In view of this, several methods of heating using near-field light that is non-propagating light have been proposed (see Patent Document 1, etc.). In this method, laser light of an appropriate wavelength is collected by an optical system, irradiated with a metal with a size of several tens of nm (called a plasmon probe) to generate near-field light, and the near-field light is heated by means of heating. It is used as.
JP-A-2005-116155

  In a general magnetic recording device (for example, a hard disk device), a plurality of recording disks are stacked in a narrow space, and the gap is set to 1 mm or less. For this reason, the thickness of the magnetic recording head is limited. In the optically assisted magnetic recording head and the ordinary magneto-optical recording head (MO) described in Patent Document 1, since a large optical system is arranged on the back surface of the head, the magnetic recording head is subject to the thickness limitation as described above. It cannot correspond to a device. From this point, the optically assisted magnetic recording head is required to have a very thin light guiding means and condensing means.

  In addition, when a light spot is formed on a disk using a normal lens or SIL (solid immersion lens), a large numerical aperture (NA) must be taken in order to reduce the spot size. This means that the angle of the light beam toward the condensing point is large. Since the optical assist unit in the optical assist type magnetic recording head needs to coexist with the magnetic recording unit and the magnetic reproducing unit used in a normal hard disk device, when the NA is large as described above, the light is recorded in the magnetic recording unit. Or the magnetic reproducing unit. In addition, the beam diameter and the magnetic recording head are increased in size.

  The present invention has been made in view of such a situation, and an object thereof is a small micro optical recording head capable of recording information at a high density with a small light spot, a manufacturing method thereof, a micro optical recording apparatus, and It is an object of the present invention to provide a compact optically assisted magnetic recording head capable of recording high-density information with a small optical spot, a manufacturing method thereof, and an optically assisted magnetic recording apparatus.

  In order to achieve the above object, a micro optical recording head according to a first aspect of the present invention is a micro optical recording head that uses light for information recording on a recording medium, and is a slider that moves relatively while floating on the recording medium. The slider has an optical waveguide and a plasmon probe provided at the condensing portion, and the plasmon probe is formed in a thick shape and embedded in the optical waveguide. .

  According to a second aspect of the present invention, there is provided the micro-optical recording head according to the first aspect, wherein the light guiding direction of the optical waveguide is the thickness direction of the plasmon probe and the slider, the thickness of the plasmon probe is L1, and the thickness of the slider. When the thickness is L2, the conditional expression: 1 μm <L1 <L2 is satisfied.

  According to a third aspect of the present invention, there is provided a method of manufacturing a micro optical recording head according to the first or second aspect of the present invention, wherein the core layer is partially formed when the core of the optical waveguide is formed. The plasmon probe is formed in the vicinity of the center of the core from above, the remaining core layer is formed, and then the core layer is processed into a predetermined core shape.

  An optically assisted magnetic recording head according to a fourth aspect of the invention is the micro optical recording head according to the first or second aspect of the invention, further comprising a magnetic recording element.

  A method for manufacturing an optically assisted magnetic recording head according to a fifth aspect of the invention is a method for manufacturing an optically assisted magnetic recording head according to the fourth aspect of the invention, wherein when the core of the optical waveguide is formed, the core is halfway Forming a layer, forming the plasmon probe in the vicinity of the center of the core from above, forming the remaining core layer, and then processing the core layer into a predetermined core shape .

  According to a sixth aspect of the present invention, there is provided a minute optical recording apparatus including the minute optical recording head according to the first or second aspect.

  An optically assisted magnetic recording apparatus according to a seventh aspect of the invention includes the optically assisted magnetic recording head according to the fourth aspect of the invention.

  According to the present invention, since the slider has an optical waveguide and a thick plasmon probe is embedded in the optical waveguide, the recording head and the recording apparatus including the same can be downsized, and a small light spot can be obtained. Can be obtained. Further, since the light spot size is reduced, the recording density can be increased. Embedding the plasmon probe in the optical waveguide can be easily realized by performing the film formation of the core layer in two stages, and the positioning of the plasmon probe in the optical waveguide can also be easily performed.

  Hereinafter, an optically assisted magnetic recording head according to the present invention and a magnetic recording apparatus including the same will be described with reference to the drawings. In addition, the same code | symbol is mutually attached | subjected to the part which is the same in each embodiment etc., and the corresponding part, and duplication description is abbreviate | omitted suitably.

  FIG. 1 shows a schematic configuration example of a magnetic recording apparatus (for example, a hard disk apparatus) equipped with an optically assisted magnetic recording head. This magnetic recording apparatus 10 includes a recording disk (magnetic recording medium) 2, a suspension 4 provided so as to be rotatable in the direction of arrow A (tracking direction) with a support shaft 5 as a fulcrum, and a tracking attached to the suspension 4. The housing 1 is provided with an actuator 6 for use, an optically assisted magnetic recording head 3 attached to the tip of the suspension 4, and a motor (not shown) for rotating the disk 2 in the direction of arrow B. The magnetic recording head 3 is configured to move relatively while floating on the disk 2.

  The magnetic recording head 3 is a micro-optical recording head that uses light for information recording on the disk 2, and a spot light source section composed of a semiconductor laser, an optical fiber, etc., and a recording portion of the disk 2 are spot-heated with near-infrared laser light. A light assist unit, an optical system for guiding near-infrared laser light from the light source unit to the light assist unit, a magnetic recording unit for writing magnetic information to a recording portion of the disk 2, and recording on the disk 2 A magnetic reproducing unit for reading the magnetic information. A semiconductor laser constituting the light source unit is a near-infrared light source, and laser light having a near-infrared wavelength (1550 nm, 1310 nm, etc.) emitted from the semiconductor laser is guided to a predetermined position by an optical fiber. Near-infrared laser light emitted from the light source unit is guided to the optical assist unit by the optical system, and exits from the magnetic recording head 3 through the optical waveguide of the optical assist unit. When the near-infrared laser beam emitted from the light assist part is irradiated onto the disk 2 as a minute light spot, the temperature of the irradiated part of the disk 2 temporarily rises and the coercive force of the disk 2 decreases. Magnetic information is written by the magnetic recording unit to the irradiated portion with the coercive force lowered. Details of the magnetic recording head 3 will be described below.

  2 to 5 show specific optical configurations (optical surface shape, optical path, etc.) of the magnetic recording head 3 as optical cross sections as Examples 1 to 4, and the construction data of Examples 1 to 4 are shown below. I will give you. In the construction data of each example, ri (i = 0,1,2,3, ...) is the i-th surface Si (i = 0,1,2,3, ...) counted from the light source side. ) Radius of curvature (mm), di (i = 0,1,2,3, ...) indicates the i-th axis upper surface interval (mm) counted from the light source side, and Ni (i = 1,2, ...) indicates the refractive index with respect to the used wavelength of the i-th medium counted from the light source side, and the x-axis inclination ai (i = 0,1,2,3, ...) and y-axis eccentricity bi (i = 0, 1, 2, 3,...) indicates the tilt angle (°) and the eccentricity (mm) of the surface Si in the mutually orthogonal xy coordinate systems. The light source position corresponds to the emission end face of the optical fiber 14. The NA (numerical aperture) of the light source and the wavelength used are also shown.

Example 1
NA of light source = 0.083333
Wavelength used: 1.31 (μm)
[Surface] [Radius of curvature] [Axis spacing] [Refractive index] [X-axis tilt] [Y-axis eccentricity]
S0 r0 = ∞ d0 = 0.244-a0 = 0 b0 = 0 (light source)
S1 r1 = 0.125 d1 = 0.25 N1 = 1.50358291 a1 = 0 b1 = 0
S2 r2 = -0.125 d2 = 0.03-a2 = 0 b2 = 0
S3 r3 =-d3 = 0-a3 = 35.26 b3 = 0
S4 r4 = ∞ d4 = 0.6 N2 = 3.51136585 a4 = 0 b4 = 0
S5 r5 =-d5 = 0-a5 = -70.528 b5 = 0
S6 r6 =-d6 = 0-a6 = 0 b6 = 0.20388742
S7 r7 = ∞ d7 = 0-a7 = 0 b7 = 0 (total reflection surface)
S8 r8 = ∞ d8 = -0.8 N3 = 3.51136585 a8 = 0 b8 = 0
S9 r9 =-d9 = 0-a9 = -61.03 b9 = 0
S10 r10 =-d10 = 0-a10 = 0 b10 = -0.70013749
S11 r11 = ∞ d11 = 0 N4 = 3.51136585 a11 = 0 b11 = 0
S12 r12 = ∞ a12 = 0 b12 = 0

Example 2
NA of light source = 0.083333
Wavelength used: 1.31 (μm)
[Surface] [Radius of curvature] [Axis spacing] [Refractive index] [X-axis tilt] [Y-axis eccentricity]
S0 r0 = ∞ d0 = 0.1-a0 = 0 b0 = 0 (light source)
S1 r1 = 0.075 d1 = 0.15 N1 = 1.75030841 a1 = 0 b1 = 0
S2 r2 = -0.075 d2 = 0.02-a2 = 0 b2 = 0
S3 r3 =-d3 = 0-a3 = 35.26 b3 = 0
S4 r4 = ∞ d4 = 0.2 N2 = 3.51136585 a4 = 0 b4 = 0
S5 r5 =-d5 = 0-a5 = -70.528 b5 = 0
S6 r6 =-d6 = 0-a6 = 0 b6 = 0.067962472
S7 r7 = ∞ d7 = 0-a7 = 0 b7 = 0 (total reflection surface)
S8 r8 = ∞ d8 = -0.4 N3 = 3.51136585 a8 = 0 b8 = 0
S9 r9 =-d9 = 0-a9 = -61.03 b9 = 0
S10 r10 =-d10 = 0-a10 = 0 b10 = -0.35006874
S11 r11 = ∞ d11 = 0 N4 = 3.51136585 a11 = 0 b11 = 0
S12 r12 = ∞ a12 = 0 b12 = 0

Example 3
NA of light source = 0.083333
Wavelength used: 1.31 (μm)
[Surface] [Radius of curvature] [Axis top spacing] [Refractive index] [X-axis tilt] [Y-axis eccentricity]
S0 r0 = ∞ d0 = 0.0402565-a0 = 0 b0 = 0 (light source)
S1 r1 = 0.075 d1 = 0.15 N1 = 1.50358291 a1 = 0 b1 = 0
S2 r2 = -0.075 d2 = 0.005-a2 = 0 b2 = 0
S3 r3 =-d3 = 0-a3 = 42.4 b3 = 0
S4 r4 =-d4 = 0-a4 = 0 b4 = 0.04259
S5 r5 = 0.0466425 d5 = 0.0466425 N2 = 1.50358291 a5 = 0 b5 = 0
S6 r6 = ∞ d6 = 0 N3 = 1.50358291 a6 = 0 b6 = 0
S7 r7 = ∞ d7 = 0.3 N4 = 3.51136585 a7 = 0 b7 = 0
S8 r8 =-d8 = 0-a8 = -70.528779 b8 = 0
S9 r9 =-d9 = 0-a9 = 0 b9 = 0.14647875
S10 r10 = ∞ d10 = 0-a10 = 0 b10 = 0 (total reflection surface)
S11 r11 = ∞ d11 = -0.25 N5 = 3.51136585 a11 = 0 b11 = 0
S12 r12 =-d12 = 0-a12 = -54.738842 b12 = 0
S13 r13 =-d13 = 0-a13 = 0 b13 = -0.20163192
S14 r14 = ∞ d14 = 0 N6 = 3.51136585 a14 = 0 b14 = 0
S15 r15 = ∞ a15 = 0 b15 = 0

Example 4
NA of light source = 0.083333
Wavelength used: 1.31 (μm)
[Surface] [Radius of curvature] [Axis spacing] [Refractive index] [X-axis tilt] [Y-axis eccentricity]
S0 r0 = ∞ d0 = 0.293245-a0 = 0 b0 = 0 (light source)
S1 r1 = 0.15 d1 = 0.3 N1 = 1.50358291 a1 = 0 b1 = 0
S2 r2 = -0.15 d2 = 0.05-a2 = 0 b2 = 0
S3 r3 =-d3 = 0.035-a3 = -54.73561 b3 = 0
S4 r4 =-d4 = 0-a4 = 0 b4 = -0.049497475
S5 r5 = ∞ d5 = 0-a5 = 0 b5 = 0 (reflecting surface)
S6 r6 = ∞ d6 = 0-a6 = 0 b6 = 0
S7 r7 =-d7 = -0.15-a7 = -54.73561 b7 = 0
S8 r8 =-d8 = 0-a8 = 0 b8 = 0
S9 r9 = ∞ d9 = 0-a9 = 0 b9 = 0
S10 r10 = ∞ a10 = 0 b10 = 0

  Examples 1 to 3 (FIGS. 2 to 4) are types of magnetic recording heads having total reflection in the optical path, and Example 4 (FIG. 5) is a type of magnetic recording head having no total reflection in the optical path. This also corresponds to the magnetic recording head 3 in FIG. 2-5, 11 is a slider, 12A is an optical assist unit having an optical waveguide, 12B is a magnetic recording unit, 12C is a magnetic reproducing unit, 13 is a silicon bench, 14 is an optical fiber, 15 is a spherical lens, and 19 is a substrate. 2 to 4, 17 is a microprism, 16 is a hemispherical lens in FIG. 4, and 18 is a micromirror in FIG. 5.

  In Examples 1 to 4, the magnetic recording unit 12B is a magnetic recording element that writes magnetic information to the disk 2, and the magnetic reproducing unit 12C is a magnetic reproducing element that reads magnetic information recorded on the disk 2. The optical assist unit 12A is an optical assist element for spot-heating the recording portion of the disk 2 with near infrared laser light. In each embodiment, the magnetic reproducing unit 12C, the optical assist unit 12A, and the magnetic recording unit 12B are arranged in this order from the inflow side to the outflow side of the recording area of the disk 2, but the arrangement order is not limited to this. Since the magnetic recording unit 12B may be positioned immediately after the outflow side of the optical assist unit 12A, for example, the optical assist unit 12A, the magnetic recording unit 12B, and the magnetic reproducing unit 12C may be arranged in this order.

  The magnetic recording heads 3 of the first and second embodiments are an optical system including a light source unit including an optical fiber 14 and a spherical lens 15 and a microprism 17 for guiding near-infrared laser light from the optical fiber 14 to the optical assist unit 12A. And a silicon bench 13 to which the light source unit and the optical system are attached, and a slider 11 that moves relatively while floating on the disk 2 (FIG. 1) with the silicon bench 13 attached. The magnetic recording head 3 according to the third embodiment includes a light source unit including an optical fiber 14, and a spherical lens 15, a hemispherical lens 16, and a microprism 17 for guiding the near infrared laser light from the optical fiber 14 to the light assist unit 12 </ b> A. An optical system, a silicon bench 13 to which the light source unit and the optical system are attached, and a slider 11 that moves relatively while floating on the disk 2 (FIG. 1) with the silicon bench 13 attached. Yes. The magnetic recording head 3 according to the fourth embodiment includes a light source unit including an optical fiber 14, an optical system including a spherical lens 15 and a micromirror 18 for guiding near-infrared laser light from the optical fiber 14 to the light assist unit 12A, and A silicon bench 13 to which the light source unit and the optical system are attached, and a slider 11 that moves relatively while floating on the disk 2 (FIG. 1) with the silicon bench 13 attached. In the slider 11 in the first to fourth embodiments, an optical assist unit 12 </ b> A, a magnetic recording unit 12 </ b> B, and a magnetic reproducing unit 12 </ b> C are provided in an integrated state with the slider 11. In the first to third embodiments, the microprism 17 is configured integrally with the silicon bench 13, and in the fourth embodiment, the micromirror 18 is configured integrally with the silicon bench 13.

  The optical configuration of Example 1 (FIG. 2) will be described. The silicon bench 13 is provided with a V groove (not shown) by anisotropic etching, and an optical fiber 14 having a diameter of 125 μm is installed in the V groove. Since the light emitting side end face of the optical fiber 14 is cut obliquely, the light beam exits from the optical fiber 14 to the lower right and then enters the spherical lens 15. The spherical lens 15 is an equal-magnification optical system composed of a glass sphere (BK7) having a diameter of 0.25 mm, and the light beam that has passed through the spherical lens 15 is totally reflected by the silicon microprism 17 integrated with the silicon bench 13. Deflected. The silicon microprism 17 has an apex angle of about 70 ° and is formed by anisotropic etching. The light beam deflected by the silicon microprism 17 is collected on the optical waveguide in the light assist portion 12A immediately below, and the coupling with the optical waveguide is completed. The mode field diameter of the optical fiber 14 is about 9 μm, and the mode field diameter of the optical waveguide in the optical assist portion 12A is also about 9 μm. Therefore, the magnification of this optical system is 1: 1. When the light beam emitted from the light assist portion 12A is irradiated onto the disk 2 (FIG. 1) as a minute light spot, the temperature of the irradiated portion of the disk 2 temporarily rises and the coercive force of the disk 2 decreases. Magnetic information is written by the magnetic recording unit 12B to the irradiated portion in which the coercive force is reduced.

  The optical configuration of Example 2 (FIG. 3) will be described. The silicon bench 13 is provided with a V groove (not shown) by anisotropic etching, and an optical fiber 14 having a diameter of 125 μm is installed in the V groove. Since the light emitting side end face of the optical fiber 14 is cut obliquely, the light beam exits from the optical fiber 14 to the lower right and then enters the spherical lens 15. The spherical lens 15 is an equal-magnification optical system composed of a sapphire glass sphere having a diameter of 0.15 mm, and the light beam that has passed through the spherical lens 15 is deflected by total reflection at a silicon microprism 17 integrated with the silicon bench 13. The The silicon microprism 17 has an apex angle of about 70 ° and is formed by anisotropic etching. The light beam deflected by the silicon microprism 17 is collected on the optical waveguide in the light assist portion 12A immediately below, and the coupling with the optical waveguide is completed. The mode field diameter of the optical fiber 14 is about 9 μm, and the mode field diameter of the optical waveguide in the optical assist portion 12A is also about 9 μm. Therefore, the magnification of this optical system is 1: 1. When the light beam emitted from the light assist portion 12A is irradiated onto the disk 2 (FIG. 1) as a minute light spot, the temperature of the irradiated portion of the disk 2 temporarily rises and the coercive force of the disk 2 decreases. Magnetic information is written by the magnetic recording unit 12B to the irradiated portion in which the coercive force is reduced.

  The optical configuration of Example 3 (FIG. 4) will be described. The silicon bench 13 is provided with a V groove (not shown) by anisotropic etching, and an optical fiber 14 having a diameter of 125 μm is installed in the V groove. Since the light emission side end face of the optical fiber 14 is cut obliquely, the light beam is emitted from the optical fiber 14 to the upper right and then enters the spherical lens 15. The spherical lens 15 is made of a glass sphere (BK7) having a diameter of 0.15 mm, and the luminous flux is substantially collimated by the spherical lens 15. The light beam that has passed through the spherical lens 15 enters the hemispherical lens 16. The hemispherical lens 16 is formed of a glass hemisphere (BK7) having a diameter of 0.093285 mm, and is bonded to a silicon microprism 17 integrated with the silicon bench 13. The substantially collimated light beam emitted from the spherical lens 15 is condensed by the hemispherical lens 16 and then deflected by total reflection by the silicon microprism 17. The silicon microprism 17 has an apex angle of about 70 ° and is formed by anisotropic etching. The light beam deflected by the silicon microprism 17 is collected on the optical waveguide in the light assist portion 12A immediately below, and the coupling with the optical waveguide is completed. The mode field diameter of the optical fiber 14 is about 9 μm, and the mode field diameter of the optical waveguide in the optical assist portion 12A is also about 9 μm. Therefore, the magnification of this optical system is 1: 1. When the light beam emitted from the light assist portion 12A is irradiated onto the disk 2 (FIG. 1) as a minute light spot, the temperature of the irradiated portion of the disk 2 temporarily rises and the coercive force of the disk 2 decreases. Magnetic information is written by the magnetic recording unit 12B to the irradiated portion in which the coercive force is reduced.

  The optical configuration of Example 4 (FIG. 5) will be described. The silicon bench 13 is provided with a V groove (not shown) by anisotropic etching, and an optical fiber 14 having a diameter of 125 μm is installed in the V groove. Since the light emitting side end face of the optical fiber 14 is cut obliquely, the light beam exits from the optical fiber 14 to the lower right and then enters the spherical lens 15. The spherical lens 15 is an equal-magnification optical system composed of a glass sphere (BK7) having a diameter of 0.3 mm, and the light beam that has passed through the spherical lens 15 is deflected by reflection from a silicon micromirror 18 integrated with the silicon bench 13. Is done. The silicon micromirror 18 has an angle of about 54 ° with the slider 11 and is formed by anisotropic etching. The surface of the silicon micromirror 18 is coated with aluminum. The light beam deflected by the silicon micromirror 18 is condensed on the optical waveguide in the light assist portion 12A immediately below, and the coupling with the optical waveguide is completed. The mode field diameter of the optical fiber 14 is about 9 μm, and the mode field diameter of the optical waveguide in the optical assist portion 12A is also about 9 μm. Therefore, the magnification of this optical system is 1: 1. When the light beam emitted from the light assist portion 12A is irradiated onto the disk 2 (FIG. 1) as a minute light spot, the temperature of the irradiated portion of the disk 2 temporarily rises and the coercive force of the disk 2 decreases. Magnetic information is written by the magnetic recording unit 12B to the irradiated portion in which the coercive force is reduced.

  Next, the optical assist unit 12A included in the slider 11 of the magnetic recording head 3 of Examples 1 to 4 (FIGS. 2 to 5) will be described with a specific example. 6 to 8 show specific examples of the light assist unit 12A. 6 is a perspective view showing an internal structure of a specific example of the light assist portion 12A, and FIG. 7 is a view from the light input side (that is, the upper surface side in the arrangement shown in FIGS. 2 to 5) with respect to the light assist portion 12A. The external appearance of the slider 11 is shown. 8 shows a cross-sectional structure of the slider 11. FIG. 8A is a cross-sectional view taken along the line AA 'in FIG. 7 (corresponding to the cross-sections of FIGS. 2 to 5), and FIG. FIG. 8 shows cross sections taken along line BB ′ in FIG. 7 (cross sections viewed from the outflow side of the recording area of the disk 2 (FIG. 1)).

The optical assist unit 12A shown in FIGS. 6 to 8 is provided in an optical waveguide composed of a core 31 (for example, Si), a sub-core 32 (for example, SiON), and a clad 33 (for example, SiO ₂ ), and a condensing portion of the optical waveguide A plasmon probe 30 is provided. The plasmon probe 30 is composed of a plasmon excitation antenna made of a pin-shaped metal thin film (material examples: gold, silver, aluminum, etc.), and has a thick shape and an optical waveguide (specifically, the core 31). Embedded in the light output side part). As shown in FIG. 8B, the width in the width direction of the optical waveguide is such that the width D3 on the light input side of the core 31 is 100 nm or less and the width D2 on the light output side is 300 nm. The width D1 is 20 nm or less. Further, when the light guiding direction by the optical waveguide is the thickness direction of the plasmon probe 30 and the slider 11, the thickness of the plasmon probe 30 is L1, and the thickness of the slider 11 is L2, as shown in FIG. Formula: 1 μm <L1 <L2 is satisfied.

  By embedding a plasmon probe including a thick antenna in a three-dimensional optical waveguide as shown in FIG. 6 and the like, it is not necessary to align the focal point and the plasmon probe after forming the optical waveguide. In such a configuration, the plasmon probe can be easily aligned. For example, when a plasmon probe is attached as an aperture or an antenna to a condensing point of an optical waveguide, alignment with the condensing point is difficult. However, if the plasmon probe is embedded in the optical waveguide, it is possible to perform highly accurate alignment as a series of operations during core processing. In addition, the configuration in which the plasmon probe is embedded in the optical waveguide has an advantage that the positional deviation is less likely to occur between the condensing point and the plasmon probe as compared with the configuration in which the plasmon probe is embedded in the SIL. Therefore, in a minute optical recording head that uses light for recording information on a recording medium, a slider that moves relatively while floating on the recording medium is provided, an optical waveguide is provided on the slider, and the light collecting portion is It is preferable to provide a plasmon probe having a thick shape so as to be embedded in the optical waveguide.

  When a plasmon probe having a thick shape is used, if the thickness is set to a certain level, tolerance for a cutting position error is improved when the end face is processed. Since about one-tenth of the blade width is an error, the conditional expression: 1 μm <L1 should be satisfied. Further, since it does not make sense to make the thickness L1 equal to or greater than the slider thickness L2, it can be said that it is preferable to satisfy the conditional expression: 1 μm <L1 <L2.

  When light acts on the plasmon probe 30, near-field light is generated near the apex of the plasmon probe 30, and recording or reproduction using light with a very small spot size can be performed. That is, if a localized plasmon is generated by providing a plasmon probe in the light output side portion of the optical waveguide, the size of the light spot formed in the optical waveguide can be further reduced, which is advantageous for high-density recording. . In addition, when silicon is used as the core material, since the refractive index of silicon is high, the near-field generation efficiency is improved. Note that the apex of the plasmon probe 30 is preferably located at the center of the core 31, and gold is preferably used as a material for the metal thin film at a near infrared wavelength (1550 nm).

  The spot diameter required for ultra-high-density recording by the optical assist method is about 20 nm, and the mode field diameter (MFD) of the plasmon probe 30 is preferably about 0.3 μm in consideration of the light utilization efficiency. Since it is difficult to make light incident with the size as it is, it is necessary to perform spot size conversion to reduce the spot diameter from about 5 μm to several hundreds of nm. In the specific examples (FIGS. 6 to 8) of the light assist unit 12A, a spot size converter is configured by at least a part of the optical waveguide to perform spot size conversion for facilitating light incidence.

  The width of the core 31 in the light assist portion 12A shown in FIGS. 6 to 8 is constant from the light input side to the light output side in the cross section shown in FIG. 8A, but is shown in FIG. 8B. The cross section changes so as to gradually widen from the light input side to the light output side in the sub-core 32. The mode field diameter is converted by the smooth change of the optical waveguide diameter. That is, the width of the core 31 of the optical waveguide in this specific example is D3 = 100 nm or less on the light input side and D2 = 300 nm on the light output side as shown in FIG. Then, an optical waveguide having an MFD of about 5 μm is formed by the sub-core 32, and thereafter, the mode field diameter is reduced by gradually optically coupling to the core 31. As described above, the mode field diameter is converted by smoothly changing the optical waveguide diameter so that [mode field diameter on the optical input side of the optical waveguide]> [mode field diameter on the optical output side of the optical waveguide] is satisfied. It is preferable to make it.

If the tip of the optical waveguide is gradually made thinner (or thinner), the amount of light leaking into the cladding will be reduced when the light propagating through the core of the optical waveguide reaches the core portion of the optical waveguide for spot size conversion. This increases the electric field distribution of light. As a result, the spot size increases. However, when the width of the core of the conversion optical waveguide is made extremely thin or thin, the propagation mode cannot exist as the optical waveguide, that is, a cut-off state is obtained. At this time, the light can be combined with an optical waveguide composed of a sub-core (eg, SiON) and a clad (eg, SiO ₂ ) to form a large light spot. This is an explanation in the direction of enlarging a small spot, but the light spot can be reduced if light having the same shape as the light spot magnified as described above is incident due to the reversibility of light. Even if the direction of thinning or thinning is one direction, the light spot can be expanded two-dimensionally.

  As described above, when a light spot is formed on a disk with a normal lens or SIL, the NA must be increased in order to reduce the spot size. This means that the angle of the light beam toward the condensing point is large, so that the light interferes with the magnetic recording unit and the magnetic reproducing unit, and also increases the beam diameter and the magnetic recording head. It also becomes. On the other hand, in the magnetic recording head 3 described above, since the slider 11 has an optical waveguide, the positional interference with the magnetic recording unit and the magnetic reproducing unit does not cause a problem. Further, if the mode field diameter at the upper part of the slider 11 is increased by a spot size converter composed of at least a part of the optical waveguide, the NA of the upper lens can be reduced and the beam diameter can be reduced. Therefore, it can contribute to miniaturization of the optical system.

  Usually, the length of the optical waveguide portion is made to coincide with the slider thickness, but may be before and after in a special configuration. For example, when a concave shape (or convex shape) is provided on the slider for alignment and a convex shape (or concave shape) is provided on the silicon bench, the length of the optical waveguide portion does not match the slider thickness. May be. Moreover, it is preferable that the length of a spot size converter is 0.2 mm or more. This is because when spot size conversion is performed rapidly, leaked light is generated, and a length of 0.2 mm or more is required to reduce this excess loss. The length of the spot size converter in the specific examples shown in FIGS. 6 to 8 is the length of the portion where the width of the core 31 gradually changes from the light input side to the light output side, that is, the length of the sub-core 32. It corresponds to.

Next, a method for manufacturing the slider 11 having the light assist portion 12A (FIGS. 6 to 8) will be described with reference to the process diagrams of FIGS. 9 shows the manufacturing process of the slider 11, and FIGS. 10 and 11 show the manufacturing processes 1 and 2 of the plasmon probe 30 in FIG. 9, respectively. As shown in FIG. 9A, after the magnetic reproducing portion 12C is formed on the substrate 19 (material: AlTiC or the like), it is flattened, and the first SiO ₂ layer 20 is formed to 6 μm by using CVD (Chemical Vapor Deposition). Film. Then, a recess having a depth of 3 μm is formed in the SiO ₂ layer 20 for the sub-core 32 by a photolithography process, and the first SiON layer 21 is formed in the recess by using CVD (FIG. 9B). On the SiO ₂ layer 20 and the SiON layer 21, as shown in FIG. 9C, a first Si layer (core layer) 22a is formed. At this time, when the plasmon probe 30 is manufactured in the manufacturing process 1 described later, the Si layer 22a is formed to a thickness of 150 nm, and when the plasmon probe 30 is manufactured in the manufacturing process 2, the Si layer 22a is formed to a thickness of 250 nm.

  Next, the manufacturing process of the plasmon probe 30 is started. In the manufacturing process 1 shown in FIG. 10, a resist is applied on the first Si layer (core layer) 22a, and a groove shape of 20 nm (corresponding to the width D1 in FIG. 8B) is formed by electron beam lithography. Patterning is performed to form a resist pattern 26 as shown in FIG. Then, when gold is deposited by vapor deposition, sputtering, or the like, a gold thin film 27 is obtained as shown in FIG. Through the lift-off process, a gold wire shape is formed from the gold thin film 27 as shown in FIG. Next, as shown in FIGS. 9D and 10D, a second Si layer (core layer) 22b is formed to a thickness of 150 nm. A resist is applied thereon, and the core shape is patterned by electron beam lithography to form a resist pattern. At this time, the resist pattern is formed so that the core shape has a desired taper shape. The first and second Si layers 22a and 22b are processed using RIE (Reactive Ion Etching) to form the core 31 as shown in FIGS. 9E and 10E.

  In the manufacturing process 2 shown in FIG. 11, a resist is applied on the first Si layer (core layer) 22a, and a groove shape of 150 nm (corresponding to the width D1 in FIG. 8B) is formed by electron beam lithography. Patterning is performed to form a resist pattern 26 as shown in FIG. Then, as shown in FIG. 11B, the Si layer 22a is processed into a V-groove shape by dry etching. Next, when gold is deposited by vapor deposition, sputtering or the like, a gold thin film 27 is obtained as shown in FIG. As shown in FIG. 11D, the gold thin film 27 other than the V-groove is removed and flattened by a polishing process. Next, as shown in FIGS. 9D and 11E, a second Si layer (core layer) 22b is formed to a thickness of 50 nm. A resist is applied thereon, and the core shape is patterned by electron beam lithography to form a resist pattern. At this time, the resist pattern is formed so that the core shape has a desired taper shape. Using RIE, the first and second Si layers 22a and 22b are processed to form the core 31 as shown in FIGS. 9 (E) and 11 (F).

After forming the core 31 in which the plasmon probe 30 is embedded in the manufacturing process 1 or 2, the second SiON layer 23 is laminated on the core 31 by 3 μm using CVD as shown in FIG. The SiON layer 23 is processed to a width of 3 μm by a photolithography process, and a sub-core 32 is formed as shown in FIG. As shown in FIG. 9 (G), the second SiO ₂ layer 24 is formed to a thickness of 8 μm using CVD and then flattened to produce the magnetic recording portion 12B. As shown in FIG. 9 (H), it is cut into a slider shape by a processing method such as dicing or milling. The clad 33 is composed of the SiO ₂ layer 20 and the SiO ₂ layer 24. The substrate 19 is made of AlTiC, but may be made of silicon.

  As a modification of the light assist unit shown in FIGS. 6 to 8, one surface of the core 31 can be configured to coincide with one surface of the sub-core 32 as shown in the top view of FIG. 17. In this way, the manufacturing process of FIG. 9B can be omitted, and the manufacturing process of the optical assist unit can be simplified.

  As described above, when the core of the optical waveguide was formed, the core layer was formed halfway, the plasmon probe was formed near the center of the core from above, and the remaining core layer was formed. Then, it is preferable to process the core layer into a predetermined core shape. By embedding the plasmon probe in the optical waveguide in this way, it becomes possible to perform positioning of the plasmon probe as a series of operations at the time of core processing with high accuracy and simplicity. In an optical waveguide having such a configuration, an optical waveguide is formed. Positioning with a later condensing point becomes unnecessary.

  Like the optical waveguide, the core material is preferably silicon, and the wavelength used for the optical waveguide is preferably a near infrared wavelength. Various high-refractive-index materials are generally known. By using these high-refractive-index materials, it is possible to cope with various wavelengths from ultraviolet light to visible light and near-infrared light. There are a wide range of options for system components. However, in general, a high refractive index material has a low etching rate even when processed with a dry etching apparatus, and it is difficult to obtain a selective ratio with a resist, and it is difficult to form a fine structure with good performance. For example, visible light can be used for materials such as GaAs and GaN, but processing is difficult. Silicon is a common material for semiconductor processes, and its processing method has been established, so that it can be processed relatively easily. Therefore, it is preferable to use silicon as the core material of the optical waveguide. However, when silicon is used as the core material of the optical waveguide, visible light cannot be used. Therefore, it is preferable to use near infrared light as the light used for the optical waveguide. In other words, if a light source having a near infrared wavelength (1550 nm, 1310 nm, etc.) is used, proven silicon can be used as a core material, which is advantageous in improving workability.

Since the refractive index of silicon is much higher than that of quartz, by using silicon as the core material of the optical waveguide, the refractive index difference Δn between the core and the cladding can be increased, and a small spot (that is, a simple structure) High energy density) can be obtained. For example, if the core is made of silicon and the clad is made of SiO ₂ as described above, the refractive index difference Δn can be increased, and the spot diameter can be reduced to 1 μm or less and about 0.5 μm. The refractive index difference Δn between the core and the clad is expressed by the equation: Δn (%) = (n1) where n1 is the refractive index of the core (here, silicon or the like) and n2 is the refractive index of the clad (here, SiO ₂ or the like). ² -n2 ²⁾ / (defined by ^{2 · n1 2) × 100 ≒} (n1-n2) / n1 × 100. The refractive index of SiO ₂ is 1.465, the refractive index of SiON is 1.5, the refractive index of Si is 3.5, and the spot diameter obtained with an optical waveguide whose core material is quartz is about 10 μm.

  In the optical waveguide, the refractive index difference Δn between the core and the clad is desirably 20% or more. By using an optical waveguide having a high refractive index difference in which Δn is 20% or more, it is possible to obtain a minute spot with a simple configuration. Since the beam diameter of the fundamental mode is 1 μm or less, the refractive index difference Δn needs to be 20% or more. The 1 μm is a beam diameter necessary for exciting plasmons with high efficiency. The refractive index difference Δn is 50% or less. This is because, no matter how high the refractive index of the core, the Δn equation only approaches 50%.

As described above, silicon is an effective core material for near-infrared wavelengths. However, if processing advantages are not required, by using another high refractive index material as the core material, visible light from ultraviolet light can be obtained. , The effect of a minute spot can be obtained in a wide wavelength range up to near infrared light. Examples of high refractive index materials (wavelength range) other than silicon include diamond (all visible range); III-V semiconductors: AlGaAs (near infrared, red), GaN (green, blue) GaAsP (red, orange, blue) ), GaP (red, yellow, green), InGaN (blue green, blue), AlGaInP (orange, yellow orange, yellow, green); II-VI group semiconductor: ZnSe (blue). Examples of processing methods for high refractive index materials other than silicon include dry etching with O ₂ gas for diamond, and Cl ₂ gas or methane hydrogen for GaAs, GaP, ZnSe, and GaN systems. For example, dry etching using an ICP etching apparatus.

  As described above, it is preferable to use an optical waveguide having a core made of silicon or the like, which is a high refractive index material, and the light spot can be reduced by the high refractive index of the core. However, when an optical waveguide is connected to the upper part of the slider with the small spot size (when a spot size converter is not used), it is necessary to use an optical system with a large NA in order to make light incident on the optical waveguide. . Therefore, it is necessary to use a highly accurate lens such as an aspheric lens as the optical system. In general, thermoforming is used to manufacture a high-precision lens such as an aspherical lens. However, there is a problem associated with mold manufacture in thermoforming, and it is necessary to maintain the accuracy of the lens surface during molding. For this reason, the lens needs to have a certain size, and the current lower limit is about φ1.5 mm.

  Further, as described above, in a disk device such as a hard disk device, it is general to use a plurality of recording disks in order to increase the capacity (see FIG. 1). In that case, the magnetic recording head is required to be thin enough to move in the gap. Even when a plurality of sheets are not used, in a small hard disk device or the like, the space between the housing wall and the disk is thin, and similarly, the magnetic recording head needs to be thin. The space is about 1 mm. However, when the optical waveguide as described above is used, an optical system with a high NA is required, and a high-precision lens such as an aspheric lens, that is, a lens having a certain size is required, and this request cannot be satisfied. . In addition, the placement accuracy required for the slider and the optical system depends on the light spot size of the optical waveguide on the light input side. From this viewpoint, it is compared with the light spot on the light output side (recording unit side). Therefore, the light spot on the light input side needs to be large.

  In the magnetic recording head 3 described above, by using a spot size converter, the light spot on the light input side is made larger than the light spot on the light output side. As a result, since an optical system with a small NA can be used, it becomes possible to use a lens (for example, a ball lens or a diffractive lens) that has a simple configuration and can be easily miniaturized, and the optical system can be made thin. This is possible for the first time. In addition, the arrangement accuracy required for the slider and the optical system is reduced, which is advantageous during assembly.

  From the above requirements, when the mode field diameter on the light output side of the optical waveguide is d and the mode field diameter on the light input side of the optical waveguide is D, the mode field diameter is converted by smoothly changing the optical waveguide diameter. Therefore, it is desirable to satisfy D> d. For example, in the specific example, D = 5 μm and d = 0.3 μm. By changing the mode field diameter by smoothly changing the optical waveguide diameter, the mode field diameter on the optical output side of the optical waveguide is smaller than the mode field diameter on the optical input side of the optical waveguide. It becomes possible to obtain a light spot. Further, since the light spot size is reduced, the recording density can be increased. Regarding the upper limit of magnification, there are fundamental problems during fabrication (the maximum light spot size limit that can be widened and the limit of the smallest light spot size that can be created) and the practically required value of the magnification ( Light output side size: 0.25 μm, light input side size: 10 μm) and about 40 times. Therefore, it is more desirable that the mode field diameter satisfy 40d> D> d.

  Further, the maximum height of the magnetic recording head including the optical system and the slider is the distance between the disk and the member (for example, a housing for housing the disk and the slider, or a second disk for recording). It is desirable to be smaller. A magnetic recording apparatus 10 shown in FIG. 1 has an optical waveguide for writing information on the disk 2 and moves relatively while floating on the disk 2, and an optical waveguide. The maximum height of the magnetic recording head 3 combined with the optical system that makes the light incident is smaller than the distance between the housing 1 and the disk 2 arranged so as to cover the moving path of the slider 11, and further adjacent to each other. Is smaller than the distance between the discs 2 positioned. With this configuration, the magnetic recording apparatus 10 can be reduced in size.

  The magnetic recording head 3 described above is an optically assisted magnetic recording head that uses light for information recording on the disk 2, but is a micro optical recording head that uses light for information recording on a recording medium. It has a slider that moves relatively while floating, and the slider has an optical waveguide and a plasmon probe provided at the condensing part, and the plasmon probe is embedded in the optical waveguide in a thick shape. However, the optically assisted magnetic recording head is not limited. For example, even in a recording head that performs recording such as near-field optical recording and phase change recording, the same effect can be obtained by using the optical waveguide having the characteristics described above. FIG. 12 shows a micro optical recording head 3a having such an optical waveguide 12a. The minute optical recording head 3a is configured to perform optical recording without using magnetism, and the magnetic recording head 3 of the third embodiment (FIG. 4) is the same as the magnetic recording head 3 except that the magnetic reproducing unit 12C and the magnetic recording unit 12B are not provided. It has the same configuration.

  Next, taking the magnetic recording head 3 of Example 3 (FIG. 4) as an example, position adjustment, adhesion, etc. between the silicon bench 13 and the slider 11 will be described. The light source unit (such as the optical fiber 14) and the optical system (such as the spherical lens 15) are attached to the silicon bench 13 by assembling with mechanical accuracy. On the other hand, the optical assist portion 12A, the magnetic recording portion 12B, and the magnetic reproducing portion 12C are formed in the slider 11 by the steps shown in FIGS. 9 to 11, and a floating structure (not shown) and a plasmon probe 30 are provided. Is obtained. That is, the silicon bench 13 and the slider 11 have different production directions as indicated by the double-directional arrows in FIG. Therefore, it is preferable to manufacture and assemble them separately, which is effective in improving the individual manufacturing accuracy and shortening the manufacturing time.

  Positioning of the silicon bench 13 and the slider 11 in the horizontal direction can be performed with reference to a positioning mark (+) or the like as shown in FIG. 14 while observing them from above with a camera or the like. Observation with a camera can be performed with infrared light. Since silicon is transparent to infrared wavelengths, positioning using the mark (+) as a reference is possible by using infrared light. If there are two positioning marks (+), it is possible to adjust two directions (X axis and Y axis) perpendicular to the optical axis (Z axis) and the angle θZ around the optical axis. Since there are structures such as the optical fiber 14 above the silicon bench 13, it is preferable to provide a positioning mark (+) on the back surface of the silicon bench 13.

  The tilt adjustment between the silicon bench 13 and the slider 11 can be performed using mutual interference using infrared light (tilt adjustment 1). For example, as shown by a solid line arrow in FIG. 15A, infrared light is irradiated from above the silicon bench 13 and obtained by interference between reflected light on the bottom surface of the silicon bench 13 and reflected light on the top surface of the slider 11. The tilt can be adjusted while viewing the interference fringes (FIG. 15B). The tilt adjustment can also be performed using an autocollimator using infrared light (tilt adjustment 2). FIG. 16A shows a state where adjustment is performed while measuring the tilt of the slider 11 with the autocollimator 25, and FIG. 16B shows an autocollimator image at that time. FIG. 16C shows how the autocollimator 25 adjusts while measuring the tilt of the silicon bench 13, and FIG. 16D shows an autocollimator image at that time.

  Adhesion between the silicon bench 13 and the slider 11 is preferably performed using an adhesive. Examples of the adhesive include a thermosetting adhesive (liquid, sheet-like), a two-component mixed adhesive (liquid), and an anaerobic adhesive (liquid). Examples of thermosetting adhesives (liquid, sheet-like) include (transparent) acrylic resin, epoxy resin, silicone resin, thermosetting polyimide that transmits the wavelength used, and two-component mixed adhesive (liquid ) Examples include (transparent) acrylic resin, epoxy resin, and urethane resin that transmit the wavelength used. Examples of anaerobic adhesive (liquid) are not cured while in contact with air, Examples include those that cure by blocking, and (transparent) acrylic resins (such as Loctite (trade name)) that transmit the wavelength used.

  In general, a UV curable resin used for bonding optical components is not preferable because UV does not pass through silicon or a slider material. Even if UV irradiation is attempted from the side, it is not preferable because the adhesive layer does not reach if it is thin. The type in which the substrates are bonded together by volatilization of the solvent is not preferable because the solvent cannot be volatilized because the adhesive layer is thin. A cyanoacrylate adhesive (instant adhesive) that solidifies by reacting with moisture in the air or on the surface of the object is not preferable because moisture cannot enter the bonding surface. Further, a substrate direct bonding method may be used for bonding the silicon bench 13 and the slider 11. This method is generally a method in which two kinds of substrates having different materials are bonded in an atomic order by directly pressing the two surfaces with each other and performing heating or the like. This method has the advantage of not requiring intermediate substances such as solder and adhesive.

1 is a perspective view illustrating a schematic configuration example of an optically assisted magnetic recording apparatus. FIG. 3 is a cross-sectional view showing Example 1 of the optically assisted magnetic recording head. Sectional drawing which shows Example 2 of an optically assisted magnetic recording head. Sectional drawing showing Example 3 of the optically assisted magnetic recording head. Sectional drawing which shows Example 4 of an optically assisted magnetic recording head. The perspective view which shows the specific example of a light assist part. The top view which shows the specific example of a light-assist part. Sectional drawing which shows the specific example of a light-assist part. Sectional drawing which shows the manufacturing process of the slider which has a specific example of a light-assist part. Sectional drawing which shows the manufacturing process 1 of the plasmon probe in FIG. Sectional drawing which shows the manufacturing process 2 of the plasmon probe in FIG. Sectional drawing which shows the Example of micro recording heads other than an optical assist type magnetic recording head. Sectional drawing for demonstrating the assembly of a silicon bench and a slider. The top view for demonstrating the position adjustment of the horizontal direction of a silicon bench and a slider. The figure for demonstrating the inclination adjustment 1 of a silicon bench and a slider. The figure for demonstrating the inclination adjustment 2 of a silicon bench and a slider. The top view which shows the modification of a light-assist part.

Explanation of symbols

1 Housing 2 Recording disk (recording medium)
3 Magnetic recording head (micro optical recording head)
3a Micro optical recording head 10 Magnetic recording device (hard disk device)
11 Slider 12A Optical assist part (optical assist element, optical waveguide)
12B Magnetic recording part (magnetic recording element)
12C Magnetic reproducing unit (magnetic reproducing element)
12a Optical waveguide 13 Silicon bench 14 Optical fiber (light source)
15 ball lens (optical system)
16 Hemispherical lens (optical system)
17 Microprism (optical system)
18 Micromirror (optical system)
19 Substrate 20 1st SiO ₂ layer 21 1st SiON layer 22a 1st Si layer (core layer)
22b Second Si layer (core layer)
23 Second SiON layer 24 Second SiO ₂ layer 26 Resist pattern 27 Gold thin film 30 Plasmon probe 31 Core 32 Sub-core 33 Cladding

Claims (7)

  A micro-optical recording head that uses light for recording information on a recording medium, and has a slider that moves relatively while floating on the recording medium, and the slider is a plasmon provided in an optical waveguide and a condensing portion thereof. A micro optical recording head comprising: a probe, wherein the plasmon probe has a thick shape and is embedded in the optical waveguide.   When the light guiding direction of the optical waveguide is the thickness direction of the plasmon probe and the slider, the thickness of the plasmon probe is L1, and the thickness of the slider is L2, the conditional expression 1 μm <L1 <L2 is satisfied. 2. The micro optical recording head according to claim 1, wherein   3. The method of manufacturing a micro optical recording head according to claim 1, wherein when the core of the optical waveguide is formed, the core layer is formed halfway, and the plasmon is formed on the core in the vicinity of the center of the core. A method of manufacturing a micro-optical recording head, comprising: forming a probe, forming a remaining core layer, and then processing the core layer into a predetermined core shape.   3. The optically assisted magnetic recording head according to claim 1, further comprising a magnetic recording element.   5. The method of manufacturing an optically assisted magnetic recording head according to claim 4, wherein when the core of the optical waveguide is formed, the core layer is formed halfway, and the plasmon is formed on the core in the vicinity of the center thereof. A method of manufacturing an optically assisted magnetic recording head, comprising: forming a probe, forming a remaining core layer, and then processing the core layer into a predetermined core shape.   A micro optical recording apparatus comprising the micro optical recording head according to claim 1.   An optically assisted magnetic recording apparatus comprising the optically assisted magnetic recording head according to claim 4.