JP4297199B2 - Optical head, optically assisted magnetic recording head, and optical recording apparatus - Google Patents

Description

  The present invention relates to an optical head, an optically assisted magnetic recording head, and an optical recording apparatus.

  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 its value approaches 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. For this reason, an optical recording head using near-field light generated from an optical aperture having a size equal to or smaller than the incident light wavelength is used, and an example thereof is shown below.

  The near-field light (also referred to as near-field light) head described in Patent Document 1 has a near-field light generating element on one surface of a substrate and condenses light on the near-field light generating element on the other surface. A lens is provided, and an optical waveguide that guides light from the light source to the lens. In this optical waveguide, in order from the light source side, for example, a single mode fiber is a first optical waveguide, a graded index fiber whose refractive index continuously changes from the center to the side surface is a second optical waveguide, and the refractive index is uniform. A coreless optical fiber is configured as a third optical waveguide. The exit surface of the third optical waveguide has a reflection surface that guides the guided light to a lens that collects the light on the near-field light generating element.

Patent Document 2 describes an imaging lens intended to be used for a videophone or the like including a single radial type refractive index lens having a positive refractive power at both ends that satisfy a plurality of conditional expressions. is there.
JP 2006-196140 A JP-A-9-49966

  However, in the near-field light head described in Patent Document 1, the light reflected from the optical path by the third optical waveguide is guided to a lens that focuses the near-field light generating element. For this reason, the height of the optical system of the near-field optical head needs to be high enough to include the thickness of the condensing lens that collects light and the working distance of the condensing lens in addition to the diameter of the optical waveguide. It does not become a near-field optical head. Further, the condenser lens after the optical path is reflected by the third optical waveguide by utilizing the fact that the light flux can be converged by adjusting the length of the graded index fiber (radial type gradient index lens). It can also be set as the structure which does not use. However, in this configuration, the imaging magnification becomes as large as 1.5 to 2 times, the size of the formed light spot is larger than the light spot guided by the first optical waveguide, and the aberration is also increased. It gets bigger. For example, the optical efficiency (ratio of the optical power generated from the near-field light generating element to the optical power incident on the near-field light generating element) when the imaging magnification is equal and the light is condensed on the near-field light generating element is 20%. However, when the imaging magnification is doubled, the light efficiency becomes 5% or less. If we try to compensate for this decrease in light efficiency with the output of the light source, a high output light source may be prepared and an optical element suitable for the output may be prepared. it can. In the case of a high-output light source, the light spot itself when emitted from the light source may be large.

  The imaging lens described in Patent Document 2 adjusts the refractive index in the radial direction, for example, so that the conditional expression is satisfied and the aberration correction is good. However, adjustment of the refractive index in the radial direction, which is possible if the lens diameter is about several millimeters, is a radial type refractive index distribution lens having a diameter comparable to that of a general optical fiber having a diameter of 125 μm or the like. It is difficult to apply to.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a low-height optical head and an optical recording apparatus with good optical efficiency.

  Said subject is solved by the following structures.

1. An optical head comprising a slider that moves relative to the recording medium along the surface on the surface of the recording medium, and a linear light guide that guides light from a light source to the recording medium.
The light guided by the linear light guide enters from one end face, exits from the other end face having a positive refractive power, and converges at a position away from the other end face to form a light spot. A radial type gradient index lens;
Deflection means for deflecting light emitted from the other end surface between the other end surface of the radial type gradient index lens and a position where the light spot is formed;
An optical waveguide disposed through the slider in a direction intersecting with the relatively moving direction and receiving light deflected by the deflecting means ;
The optical head according to claim 1, wherein the other end surface is in contact with a substance having a refractive index lower than an effective range of the radial type gradient index lens and has a convex shape in an emission direction .

2. An optical head comprising a slider that moves relative to the recording medium along the surface on the surface of the recording medium, and a linear light guide that guides light from a light source to the recording medium.
The light guided by the linear light guide enters from one end face, exits from the other end face having a positive refractive power, and converges at a position away from the other end face to form a light spot. A radial type gradient index lens;
Deflection means for deflecting light emitted from the other end surface between the other end surface of the radial type gradient index lens and a position where the light spot is formed;
An optical waveguide disposed through the slider in a direction intersecting with the relatively moving direction and receiving light deflected by the deflecting means;
The other end face of the contact with the material having a refractive index higher than the refractive index of the effective range of the radial type refractive index distribution lens, the optical head characterized in that the injection direction is concave shaped.

3 . 3. The optical head according to 1 or 2 , wherein a plasmon probe for generating near-field light is provided on a surface of the optical waveguide from which light is emitted.

4 . It said deflection means, the optical head according to any one of 1 to 3, characterized in that provided in the prism.

5 . It said deflection means, the optical head according to any one of 1 to 3, characterized in that the reflecting mirror.

6 . The optical head according to any one of 1 to 5 , wherein the slider includes a magnetic recording unit that performs magnetic recording on the recording medium.

7 . A recording medium, an optical recording apparatus comprising: the optically assisted magnetic recording head, and the information writing control unit, to have a described 6.

  According to the present invention, the optical head includes the linear light guide and the radial type refractive index distribution lens arranged in a straight line, and the radial type refractive index distribution lens having a positive refractive power on the exit surface. A light spot can be formed by focusing light on the extension line. The imaging magnification for forming the light spot is smaller than that of a radial type gradient index lens having no positive refractive power on the exit surface, and aberrations can be suppressed satisfactorily. Furthermore, since the optical head is provided with a deflecting means, the optical path can be deflected to 90 °, for example, and light can enter the optical waveguide. Therefore, the optical head is provided with a linear light guide and a radial type refractive index distribution lens in a direction along the surface of the recording medium, and a smaller light spot is formed at a shorter position from the exit surface of the radial type refractive index distribution lens. This light spot can be formed on the incident surface of the optical waveguide.

  Therefore, it is possible to provide an optical head having a high optical efficiency and a low height and an optical recording apparatus using the optical head.

It is a figure which shows the example of schematic structure of the optical recording device carrying an optically assisted magnetic recording head. It is a figure which shows an example of an optical recording head in a cross section. It is a figure which shows the example of the optical system of an optical recording head with an optical sectional view. It is a figure which shows the example of the optical system of an optical recording head with an optical sectional view. It is a figure which shows the example of the optical system of an optical recording head with an optical sectional view. It is a figure which shows the example of a plasmon probe. It is a figure which shows the spherical aberration of Numerical example 1. It is a figure which shows the spherical aberration of Numerical example 2. It is a figure which shows the spherical aberration of Numerical example 3. It is a figure which shows the spherical aberration of the numerical example 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing | casing 2 Disk 3 Optical recording head 4 Suspension 5 Support shaft 6 Tracking actuator 6
7 Control unit 11 Optical fiber (linear light guide)
DESCRIPTION OF SYMBOLS 12 Radial type gradient index lens 14 Optical element 14a Deflection surface 15 Slider 16 Optical waveguide (light assist part)
16f plasmon probe 17 magnetic recording unit 18 magnetic reproducing unit 50, 60, 70 optical system 100 optical recording device OP optical path LS light source FP condensing point S1, S2, S3, S4, S5 surface

  Although the present invention will be described based on the illustrated embodiment, the present invention is not limited to the embodiment.

  Hereinafter, the present invention will be described based on an optically assisted magnetic recording head having a magnetic recording element in the optical head according to the illustrated embodiment and an optical recording apparatus including the same. The present invention is not limited to the embodiment. I can't. Note that the same or corresponding parts in the respective embodiments are denoted by the same reference numerals, and redundant description will be omitted as appropriate.

FIG. 1 shows a schematic configuration example of an optical recording apparatus (for example, a hard disk apparatus) equipped with an optically assisted magnetic recording head. The optical recording apparatus 100 includes the following (1) to (6) in the housing 1.
(1) Recording disk (recording medium) 2
(2) Suspension 4 provided so as to be rotatable in the direction of arrow A (tracking direction) with support shaft 5 as a fulcrum.
(3) Tracking actuator 6 attached to the suspension 4
(4) Optically assisted magnetic recording head (hereinafter referred to as optical recording head) 3 attached to the tip of the suspension 4
(5) Motor for rotating the disk 2 in the direction of arrow B (not shown)
(6) Control unit 7 that performs information writing control of the tracking actuator 6, motor, and recording
Such an optical recording apparatus 100 is configured such that the optical recording head 3 can move relatively while flying over the disk 2.

  FIG. 2 shows an example of the optical recording head 3 in a cross-sectional view. The optical recording head 3 is an optical recording head that uses light for information recording on the disk 2, and includes an optical element 14 and a slider 15. The optical element 14 includes an optical fiber 11 that is a linear light guide that guides light from a light source (not shown), and light emitted from the optical fiber 11 as an optical waveguide (sometimes referred to as a light assist unit) 16. Are provided on a radial type gradient index lens 12 and a prism portion 14b that guide the light as a light spot, and a deflection surface 14a that is a deflection means for deflecting light is provided. The optical fiber 11 may be either with or without a core. The exit surface 13 of the radial type gradient index lens 12 is convex in the exit direction having a positive refractive power. The fact that the radial type gradient index lens 12 has positive refractive power on the exit surface 13 will be described later. The optical element 14 is provided with a groove (not shown) having a V-shaped cross-section for accurately fixing and bonding the radial type gradient index lens 12 in the light emission direction.

  The coupling between the optical fiber 11 and the radial type gradient index lens 12 depends on the material, but is preferably joined and integrated by a melting process. When integrated in this way, handling becomes easy, and at the same time, light loss at the surface where the optical fiber 11 and the radial type gradient index lens 12 are in contact is suppressed, and the light guided by the optical fiber 11 is efficiently radial type. The light can be emitted from the refractive index distribution lens 12.

  The slider 15 includes an optical waveguide 16 that emits a light spot formed on the upper surface to the disk 2, a magnetic recording unit 17 that writes magnetic information to a recorded portion of the disk 2, and magnetic information recorded on the disk 2. Is provided with a magnetic reproducing unit 18 for reading. On the exit surface of the optical waveguide 16, there is a plasmon probe 16f that generates near-field light.

  In FIG. 2, the magnetic reproducing unit 18, the optical waveguide 16, and the magnetic recording unit 17 are arranged in this order from the entry side to the withdrawal side (→ direction in the figure) of the recording area of the disk 2. Not exclusively. Since the magnetic recording unit 17 may be positioned immediately after the exit side of the optical waveguide 16, for example, the waveguide 16, the magnetic recording unit 17, and the magnetic reproducing unit 18 may be arranged in this order.

  The light guided by the optical fiber 11 is, for example, light emitted from a semiconductor laser (not shown) that is a light source. The laser light emitted from the end face of the optical fiber 11 is incident on the emission surface 13 from the upper surface of the optical waveguide 16 provided on the slider 15 through the radial refractive index distribution lens 12 having a positive refractive power and the deflection surface 14a. . At this time, it is preferable to focus the light on the upper surface of the optical waveguide 16 to form a light spot because the light can be efficiently coupled. Light incident from the upper surface of the optical waveguide 16 is guided through the optical waveguide 16 and emitted from the optical recording head 3 toward the disk 2.

The slider 15 moves relative to the disk 2 which is a magnetic recording medium while flying, but there is a possibility of contact if there is dust attached to the medium or a defect in the medium. In order to reduce wear generated in that case, it is desirable to use a hard material having high wear resistance as the material of the slider 15. For example, a ceramic material containing Al ₂ O ₃ , AlTiC, zirconia, TiN, or the like may be used. Further, as a wear prevention treatment, a surface treatment may be performed on the surface of the slider 15 on the disk 2 side in order to increase wear resistance. For example, when a DLC (Diamond Like Carbon) film is used, the light transmittance is high and a hardness of Hv = 3000 or more after diamond is obtained.

  Further, the surface of the slider 15 facing the disk 2 has an air bearing surface (also referred to as an ABS (Air Bearing Surface) surface) for improving the flying characteristics. The flying of the slider 15 needs to be stabilized in the state of being close to the disk 2, and it is necessary to appropriately apply a pressure for suppressing the flying force to the slider 15. For this reason, the suspension 4 fixed on the optical element 14 has not only a function of tracking the optical recording head 3 but also a function of appropriately applying a pressure for suppressing the flying force of the slider 15.

  When the laser beam emitted from the optical recording head 3 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 17 to the irradiated portion in which the coercive force is reduced.

  The radial type gradient index lens 12 will be described. The radial type refractive index distribution lens is configured such that incident light propagates in the lens with a sinusoidal characteristic period in the optical path. When the length of a radial type refractive index distribution lens whose both ends are flat is exactly matched to an integral multiple of the inherent period of the radial type refractive index distribution lens, the exit surface of the optical fiber is connected to one end surface (incident surface), and the other A light spot having a size substantially equal to that of the light spot emitted from the optical fiber can be formed on the end face (exit surface).

  On the other hand, as described above, in configuring an optical recording head, it is necessary to guide light guided from a light source using an optical fiber or the like onto the recording medium surface. Since it is desired to reduce the size of the optical recording head (for example, about 1 mm × 1 mm × 1 mm), it is necessary to arrange the optical fiber so as to be substantially parallel to the recording medium surface. There is. For this purpose, a deflecting means such as a mirror for deflecting the optical path by 90 ° is required.

By using the fact that the optical path in the radial type refractive index distribution lens has a sinusoidal characteristic period P, the length of the radial type refractive index distribution lens whose both ends are flat is considered to be a specific length considering the specific period P. Set to L. A radial type refractive index distribution lens having a specific length L can form a light spot incident from the incident surface at a position away from the exit surface. Specifically, the specific length L is set to a length obtained by adding more than 1/4 of one cycle to less than 1/2, or more than 3/4 and less than 1 to n cycles (n is a natural number including 0). This is expressed by the following equations (1) and (2). (0.25 + 0.5 × n) × P <L <(0.5 + 0.5 × n) × P (1) where
P = 2 × π / A ^1/2 (2)
A ^1/2 : Constant (also referred to as refractive index distribution constant)
L: A natural number including a specific length n: 0 When this property is used, light guided to an optical fiber is incident on a radial type refractive index distribution lens. A deflection surface can be provided between them.

  However, the light spot formed by the light exiting from the radial type refractive index distribution lens having a flat end at both ends and having a specific length L as described above is sufficiently close to the exit surface in reducing the position of the optical recording head. Cannot be done, and there are many aberrations.

  Here, like the radial type refractive index distribution lens 12 according to the present invention, the exit surface of the radial type refractive index distribution lens has a positive refractive power. By appropriately setting the length of the radial type refractive index distribution lens and the positive refractive power of the exit surface, the imaging magnification of the radial type refractive index distribution lens can be reduced from approximately 1 to less than the light spot from the exit surface. When the optical recording head is constructed, the distance and aberration to the position for forming the optical recording head can be made favorable.

  Light exiting from the optical fiber 11 enters the radial type gradient index lens 12, and light exiting from the exit surface having positive refractive power forms a light spot on the entrance surface of the optical waveguide 16 through the deflecting surface 14 a. Examples of the optical system are shown in optical cross-sectional views in FIGS. In the optical system 50 shown in FIG. 3, as in the case of FIG. 2 described so far, the light guided from the optical fiber 11 enters the radial type gradient index lens 12 and the emitted light is the optical shown in FIG. A state is shown in which the light is incident on the prism portion 14b of the element 14 and is deflected by the deflecting surface 14a that is internally reflected. The exit surface 13 of the radial type gradient index lens 12 is convex in the exit direction because it is in contact with air having a lower refractive index than the effective range of the radial type gradient index lens 12. The effective refractive index of the radial type gradient index lens 12 is about 1.5 (D line). Here, the effective range of the radial type refractive index distribution lens 12 can be determined by the NA of the radial type refractive index distribution lens 12 and the refractive index distribution. In addition, when a material having a high refractive index is used for the prism portion 14b that deflects the optical path, the prism portion 14b can be made smaller, so that the optical recording head 3 can be made smaller.

  The optical system 60 shown in FIG. 4 shows a state in which light guided from the optical fiber 11 enters the radial type gradient index lens 12 and the emitted light is deflected by a deflecting surface 14a such as a mirror surface. The exit surface of the radial type refractive index distribution lens 12 is convex in the exit direction because it is in contact with air having a refractive index lower than the effective range of the radial type refractive index distribution lens 12.

  In the optical system 70 shown in FIG. 5, the light guided from the optical fiber 11 is incident on the radial type gradient index lens 12, and the emitted light is incident on the prism portion 14b of the optical element 14 to be reflected on the inner surface. It shows how it is deflected. The exit surface of the radial type gradient index lens 12 has a concave shape. The convex shape which is the inverted shape of the concave shape is joined to the convex lens 20 having a flat surface opposite to the convex shape. The prism part 14b is joined. The convex flat lens 20 preferably has a refractive index higher than the refractive index of the effective range of the radial type refractive index distribution lens 12. For example, a high refractive index glass having a refractive index of about 1.75 (D line) is used as a material. It is preferable to do this. In addition, when a material having a high refractive index is used for the prism portion 14b for deflecting the optical path, the prism portion 14b can be made smaller, so that the optical recording head can be made smaller. There is adhesion in a method of joining the radial type refractive index distribution lens 12, the convex flat lens 20, and the prism portion 14b. For example, an adhesive for a high refractive index optical component having a refractive index of about 1.6 to 1.7 is used. And, it is preferable for suppressing a decrease in light transmission efficiency due to a difference in refractive index.

  By configuring the optical system of the optical recording head 3 as shown in FIGS. 3 to 5, the light emitted from the exit surface 13 of the radial type gradient index lens 12 can deflect the optical path by 90 °, for example. The imaging magnification can be reduced from approximately 1 to less than that, and aberrations can be suppressed satisfactorily. Therefore, an optical fiber and a gradient index lens are provided in a direction along the surface of the recording medium, and a smaller light spot can be formed at a shorter position from the exit surface of the radial gradient index lens. Can be formed on the incident surface of the optical waveguide. Therefore, light can be efficiently guided as if the optical fiber is directly coupled to the optical waveguide 16 provided so as to be substantially perpendicular to the surface of the recording medium. Therefore, an optical recording head having a high optical efficiency and a low height can be configured.

  The optical element 14 shown in FIG. 2 can be formed by an injection molding method or a press molding method using, for example, a thermoplastic resin or glass that transmits light from a light source. Examples of the thermoplastic resin include ZEONEX (registered trademark) 480R (refractive index 1.525, Nippon Zeon Co., Ltd.), PMMA (polymethyl methacrylate, for example, Sumipex (registered trademark) MGSS, refractive index 1.49, Sumitomo Chemical Co., Ltd.), PC (polycarbonate, for example, Panlite (registered trademark) AD5503, refractive index 1.585, Teijin Chemicals Ltd.), and the like. In addition, as glass, SF6 (nd = 1.805, νd = 2.40), which is a high refractive index glass used in a glass mold, a mold lens that can be molded at an extremely low temperature, for example, considering the life of the mold. PG375 (Vidron, Sumita Optical Co., Ltd., nd = 1.54250, νd = 62.9) which is an optical glass for use.

  It is preferable to provide a plasmon probe made of, for example, a triangular flat metal thin film made of gold or the like on the exit surface of the optical waveguide 16 of the optical recording head 3. Near-field light can be generated by applying light to the plasmon probe. A specific example of the plasmon probe 16f is shown in FIG.

  In FIG. 6, (A) is a plasmon probe 16f made of a triangular flat metal thin film, and (B) is a plasmon probe 16f made of a bow-tie flat metal thin film, each having a vertex P with a radius of curvature of 20 nm or less. It consists of an antenna. (C) is a plasmon probe 16f made of a flat metal thin film having an opening, and is made of an antenna having a vertex P having a radius of curvature of 20 nm or less. Examples of the material for the flat metal thin film include aluminum, gold, and silver. When light acts on these plasmon probes 16f, near-field light is generated in the vicinity of the apex P, and recording using light having a very small spot size can be performed. That is, if the plasmon is generated by providing the plasmon probe 16f at or near the light emission position of the optical waveguide 16, the size of the light spot formed by the optical waveguide 16 can be reduced, which is advantageous for high-density recording. It becomes. It is preferable that the apex P of the plasmon probe 16f is located in the center of the optical waveguide 16.

  The optical head described so far is an optically assisted magnetic recording head that uses light for information recording on the disk 2. However, the optical head uses light for information recording on a recording medium and has a magnetic reproducing unit 17 and a magnetic recording unit 18. For example, an optical head that performs recording such as near-field optical recording and phase change recording can also be used.

  Here, the construction data constituting the optical systems 50, 60, and 70 shown in FIGS. 3 to 5 are shown in Numerical Example 1 for the optical system 50, Numerical Examples 2 and 3 for the optical system 60, and for the optical system 70. Example 4 is given below.

The construction data of numerical examples 1, 2, 3, 4 are as follows. ri (i = 1, 2, 3...) indicates the radius of curvature of the i-th surface Si (i = 1, 2, 3...) counted from the light source LS side, and di (i = 1, 1). 2, 3...) Indicate the i-th axis upper surface interval (mm) counted from the light source LS side, and the focal point is FP. Further, the coordinate axes serving as a reference when defining each surface Si are shown as eccentric data and the eccentric amounts and inclination angles of the X axis, the Y axis, and the Z axis, respectively. The refractive index n (r) of the optical element having a refractive index distribution is represented by the following formula (1).
_{n (r) = n 0 ×} (1- (A 1/2 × r) 2/2) (1)
n ₀ : reference refractive index A ^1/2 : constant (unit: mm ⁻¹ )
r: Height from the optical axis (r ² = x ² + y ² )
The notation of eccentricity data will be described. The eccentric amounts of the X, Y, and Z axes are shown as XSC, YSC, and ZSC, respectively. In addition, the inclination angles of the surfaces when the X, Y, and Z axes are the rotation axes are shown as ASC, BSC, and CSC, respectively. The first coordinate axes are shown in FIGS. The direction in which light travels from the light source LS is taken as the Z axis, and the coordinates orthogonal to this are taken as the X axis and the Y axis. In this coordinate system, the surface is sequentially defined from the light source side with the position of the light source as the origin. The origin when defining the sequential surface reflects the eccentricity data shown each time. The spherical aberrations of Numerical Examples 1, 2, 3, and 4 are shown in FIGS. The vertical axis H indicates the incident height normalized based on the effective diameter.

  In numerical examples 1 to 4 below, the position of the light source LS is set in the air just 0.1 μm before the incident end face of the radial type gradient index lens 12 for easy calculation. There is virtually no impact. Further, the radii of curvature of the light source LS and the condensing point FP in Tables 1 to 4 are indicated as (∞) because they are flat for convenience of calculation.

(Numerical example 1)
Object side NA: 0.10000
Working wavelength λ: 1000 nm
Magnification: 1.0071
Refractive index distribution standard refractive index n ₀ : 1.500000 (λ = 1000 nm)
Constant A ^1/2 : 3.125 (λ = 1000 nm)
In Table 1 below, the focal point FP is in the same plane as the plane S5.

(Numerical example 2)
Object side NA: 0.10000
Working wavelength λ: 1000 nm
Magnification: 1.0071
Refractive index distribution standard refractive index n ₀ : 1.500000 (λ = 1000 nm)
Constant A ^1/2 : 3.125 (λ = 1000 nm)

(Numerical example 3)
Object side NA: 0.10000
Working wavelength λ: 1000 nm
Magnification: 0.9416
Refractive index distribution standard refractive index n ₀ : 1.500000 (λ = 1000 nm)
Constant A ^1/2 : 3.125 (λ = 1000 nm)

(Numerical example 4)
Object side NA: 0.10000
Working wavelength λ: 1000 nm
Magnification: 1.0091
Refractive index distribution standard refractive index n ₀ : 1.500000 (λ = 1000 nm)
Constant A ^1/2 : 3.125 (λ = 1000 nm)
In Table 4 below, the focal point FP is in the same plane as the plane S5.

Claims (7)

An optical head comprising a slider that moves relative to the recording medium along the surface on the surface of the recording medium, and a linear light guide that guides light from a light source to the recording medium.
The light guided by the linear light guide enters from one end face, exits from the other end face having a positive refractive power, and converges at a position away from the other end face to form a light spot. A radial type gradient index lens;
Deflection means for deflecting light emitted from the other end surface between the other end surface of the radial type gradient index lens and a position where the light spot is formed;
An optical waveguide disposed through the slider in a direction intersecting with the relatively moving direction and receiving light deflected by the deflecting means ;
The optical head according to claim 1, wherein the other end surface is in contact with a substance having a refractive index lower than an effective range of the radial type gradient index lens and has a convex shape in an emission direction . An optical head comprising a slider that moves relative to the recording medium along the surface on the surface of the recording medium, and a linear light guide that guides light from a light source to the recording medium.
The light guided by the linear light guide enters from one end face, exits from the other end face having a positive refractive power, and converges at a position away from the other end face to form a light spot. A radial type gradient index lens;
Deflection means for deflecting light emitted from the other end surface between the other end surface of the radial type gradient index lens and a position where the light spot is formed;
An optical waveguide disposed through the slider in a direction intersecting with the relatively moving direction and receiving light deflected by the deflecting means;
The other end face of the contact with the material having a refractive index higher than the refractive index of the effective range of the radial type refractive index distribution lens, the optical head characterized in that the injection direction is concave shaped. 3. The optical head according to claim 1 , further comprising a plasmon probe for generating near-field light on a surface of the optical waveguide from which light is emitted . 4. The optical head according to claim 1 , wherein the deflecting unit is provided on a prism . 4. The optical head according to claim 1 , wherein the deflecting unit is a reflection mirror . 6. The optically assisted magnetic recording head according to claim 1, wherein the slider includes a magnetic recording unit that performs magnetic recording on the recording medium . An optical recording apparatus comprising: a recording medium; the optically assisted magnetic recording head according to claim 6; and an information writing control unit .