JP2009283051A - Optical element, optical recording head and optical recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element which can efficiently condense and emit though it is compact and has simple constitution. <P>SOLUTION: The optical element includes a core layer, of which the contour shape of a part is a parabola and of which the distal end part is a flat plane, and a clad layer, in contact with the core layer and the optical element converges light coupled to the core layer to a focal point of the parabola and emits the converged light from the distal end part. In the optical element, a diffraction grating which guides projected light into the inside of the core layer and couples the guided light as light, proceeding in a direction perpendicular to the axis of the parabola, and a deflection part which deflects the light proceeding in the direction perpendicular to the axis of the parabola, in a direction parallel to the axis of the parabola are formed in the core layer, and in the diffraction grating, a plurality of grooves are formed, in parallel with the axis of the parabola with the prescribed period. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an optical element, an optical 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. Thus, several methods of heating using near-field light that is non-propagating light have been proposed (for example, Patent Documents 1 and 2).

  In the optical transducer described in Patent Document 1, electromagnetic near-field light (localized plasmon) is generated by irradiating a metal nanostructure (also called a plasmon probe) with electromagnetic radiation, for example, laser light, and the near-field light is heated. It is said. Specifically, an optical transducer couples light guided by an optical fiber or the like to a thin film planar light guide with two gratings (diffraction gratings), and the light coupled to the light guide is a metal nanostructure. Focused to expose the pins. The two gratings give a phase difference to the combined light, and the two beams are combined at the time of focusing.

In general, a light beam output from a waveguide such as a laser light source, an optical fiber, or a polymer has a unimodal circular or elliptical beam profile. When irradiating the above-mentioned two gratings with such a single-peak light beam, the central part where the light energy is high irradiates the central part where neither of the two gratings is formed, so that sufficient optical coupling cannot be performed. Therefore, efficiency is not good. As a method corresponding to this, in Patent Document 2, the first diffraction grating and the second diffraction grating which are inclined with respect to each other are alternately arranged obliquely, and the plane guide in which the gap between the intermediate portions of the two diffraction gratings is eliminated. A waveguide is shown.
JP-A-2005-116155 JP 2006-202461 A

  However, like the grating described in Patent Document 1, the diffraction grating arranged in the planar waveguide described in Patent Document 2 needs to be input at an angle with respect to the incident surface of the diffraction grating. Examples of the optical element for setting the predetermined angle include a prism, a diffraction grating, and a mirror. However, since such an optical element is required, the configuration becomes complicated, the manufacturing cost increases, and it cannot be easily assembled. There's a problem. Further, there is a problem that the optical system becomes large in order to secure an incident angle having an angle in a direction perpendicular to the increase in the number of components and the recording medium surface.

  In addition, when a beam having a unimodal profile is incident on the diffraction grating, it is necessary to align the center of the beam with the end of the adjacent side of the two diffraction gratings in order to distribute energy evenly to the two gratings. There is. Since the diffraction structure is discontinuous at this end, the diffraction efficiency is lower than when it is continuous, and the position where the most energy of the light beam that irradiates this part is aligned. There was a problem that it could not be used. In addition, since the phase difference between the two optical paths is generated, the structure of the grating is complicated and cannot be easily manufactured.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical element that can efficiently collect and emit light while having a small and simple configuration, and the optical element. It is an object to provide an optical recording head and an optical recording apparatus using the above.

  Said subject is solved by the following structures.

1. A part of the contour shape is a parabola, a core layer having a flat tip portion, and a clad layer in contact with the core layer, the light coupled to the core layer is focused on the focal point of the parabola, An optical element from which light is emitted from the tip,
In the core layer,
A diffraction grating that introduces irradiated light into the core layer at a position where the core layer is irradiated with light, and couples the introduced light as light traveling in a direction perpendicular to the parabola axis;
A deflection unit coupled by the diffraction grating and deflecting light traveling in a direction perpendicular to the parabola axis in a direction parallel to the parabola axis;
The optical element, wherein the diffraction grating has a plurality of grooves formed in parallel with the parabolic axis at a predetermined period.

  2. 2. The optical element according to 1, wherein a plasmon probe that generates near-field light by light irradiation is provided at a focal point of the parabola.

3. The optical element according to 1 or 2;
An optical recording head comprising: a light source that irradiates light to the diffraction grating of the optical element.

  4). 4. The optical recording head according to item 3, further comprising a magnetic recording unit that performs magnetic recording on the magnetic recording medium.

5. 4. An optical recording head according to 4,
A magnetic recording medium;
An optical recording apparatus comprising: a control unit configured to perform magnetic recording on the magnetic recording medium by the optical recording head.

  According to the optical element of the present invention, the light irradiated to the diffraction grating can be efficiently collected and emitted from the tip of the core layer, while having a small and simple configuration including the diffraction grating and the deflection unit in the core layer. In addition, according to the optical recording head and the optical recording apparatus of the present invention, it is possible to provide an optical element that exhibits the above-described effects.

  The present invention relates to an optical element that can be used to generate a small light spot, and can be used for, for example, a magneto-optical recording medium or an optical recording head used for recording on an optical recording medium.

  Hereinafter, the present invention will be described on the basis of an optically assisted magnetic recording head having a magnetic recording unit in the optical recording head according to the illustrated embodiment and an optical recording apparatus including the same. Not limited. 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 supported by an arm 5 provided so as to be rotatable in the direction of arrow A (tracking direction) with a support shaft 6 as a fulcrum.
(3) Tracking actuator 7 attached to arm 5
(4) Optically assisted magnetic recording head attached to the tip of the suspension 4 (hereinafter referred to as the optical recording head 3)
(5) Motor for rotating the disk 2 in the direction of arrow B (not shown)
(6) Control unit 8 that controls the optical recording head 3 such as generation of light and magnetic field to be irradiated in accordance with write information for recording on the tracking actuator 6, motor and disk 2.
Such an optical recording apparatus 100 is configured such that the optical recording head 3 can relatively move while flying over the disk 2.

  FIG. 2 conceptually shows a cross section of the recording / writing peripheral portion of an example of the optical recording head 3. The optical recording head 3 is an optical recording head that uses light for information recording on the disk 2, and includes a slider 30, an optical element 20, a magnetic recording unit 40, and the like.

  Since the slider 30 moves relative to the disk 2 while flying over the disk 2 that is a magnetic recording medium, an ABS surface 32 for improving the flying characteristics is provided on the surface of the slider 30 facing the disk 2. (Air Bearing Surface).

  The light source 50 includes, for example, a DFB laser element, a surface-emitting laser element, an optical fiber exit end, a polymer waveguide output end, and the like, and a plurality of lights that condense the light emitted from these onto a diffraction grating provided in the optical element 20 described later. A combination of an optical system having a single lens can be mentioned. The light source 50 only needs to irradiate light to the diffraction grating provided in the optical element 20, and is not limited to the above configuration. As another example, an optical element such as a microlens is integrated on the light emission surface of the surface emitting laser element. A photonic crystal edge emitting laser may be used.

  The light 52 emitted from the light source 50 irradiates the optical element 20. As will be described later, the light 52 is incident in a direction perpendicular to the irradiation surface of the optical element 20. For this reason, an optical component such as a mirror for providing an incident angle (> 0) to the optical element 20 is not required, it is not necessary to secure an arrangement space or an optical path for these optical components, and the thickness of the optical recording head 3 ( The direction perpendicular to the recording surface of the disk 2 can be made thinner. Further, the optical loss can be suppressed by reducing the number of optical components constituting the optical recording head 3. The light source 50 is fixed to the suspension 4 as shown in FIG. Placing the light source 50 away from the optical recording head 3 makes the optical recording head 3 less susceptible to the heat generated by the light source 50 and the floating of the slider 30 due to the weight of the light source 50 and additional stress generated by the light source. Is preferable in that it is not hindered.

  The optical element 20 includes a diffraction grating for inputting light, and a waveguide composed of a core layer and a cladding layer for guiding and emitting the input light. The light 52 is coupled to the waveguide, specifically the core layer, through the diffraction grating. The light coupled to the core layer proceeds to the deflecting portions disposed on both sides of the diffraction grating, and after being deflected by approximately 90 degrees, proceeds to the tip portion 24 of the core layer and is condensed.

  A pin-shaped plasmon probe 25 (hereinafter referred to as a probe) made of a metal such as gold, silver, or aluminum that generates near-field light when irradiated with light is provided at the condensing position of the distal end portion 24. The recording medium near the probe tip is heated by the generated near-field light 60. The size of the light spot by near-field light is determined by the thinness of the tip of the pin shape.For example, when the radius of curvature of the pin tip is several tens of nanometers, the size of the light spot is also several tens of nanometers, and the energy is at the probe tip. Concentrate around several tens of nanometers.

  The shape of the probe 25 may not be a cylindrical pin shape, and may be, for example, a vertically long triangular pyramid shape or a cone toward the recording surface of the disk 2. Further, since the flying height of the slider 30 with respect to the disk 2 is, for example, 10 nanometers or less, a region where the energy of near-field light is strong can be used. The optical element 20 will be described in detail later.

  When the near-field light 60 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 40 to the irradiated portion with the reduced coercive force.

  In FIG. 2, the optical element 20 and the magnetic recording unit 40 are arranged in this order from the entry side to the exit side (in the direction of arrow 2a in the figure) of the recording area of the disk 2. As described above, it is preferable that the magnetic recording unit 40 be positioned immediately after the exit side of the optical element 20 because writing can be performed before the heating of the heated recording area proceeds excessively. Further, a magnetic reproducing unit 41 that reads magnetic recording information written on the disk 2 may be provided on the exit side of the magnetic recording unit 40 or the inflow side of the optical element 20.

  The optical element 20 will be described. FIG. 3 is a front view of the optical element 20 (the side on which the light 52 is incident), FIG. 4 is a side view, and FIG. 5 is a perspective view. The optical element 20 includes a core layer 21 and a clad layer 22 constituting a waveguide, and a diffraction grating 29 into which light is input is formed in the core layer 21. The waveguide can be composed of a plurality of layers made of materials having different refractive indexes, and the refractive index of the core layer 21 is larger than the refractive index of the cladding layer 22. A waveguide is formed by this refractive index difference, and the light in the core layer 21 is confined in the core layer 21 and travels efficiently, and reaches the tip 24.

  The refractive index of the core layer 21 may be about 1.9 to 4.0, and the refractive index of the cladding layer 22 may be about 1.0 to 2.0. By forming the core layer 21 having a refractive index larger than the refractive index of the cladding layer 22, the core layer 21 can guide light more efficiently by internal reflection. As the ratio of the refractive index of the core layer 21 to the refractive index of the cladding layer 22 is increased, the core layer 21 can confine more light inside the core layer 21. Note that air is present on the opposite surface of the core layer 21 in contact with the cladding layer 22, and this air acts as the cladding layer.

The core layer 21 is formed of Ta ₂ O ₅ , TiO ₂ , ZnSe, etc., and the thickness may be in the range of about 20 nm to 500 nm, and the cladding layer 22 is formed of SiO ₂ , air, Al ₂ O _3, etc. The thickness may be in the range of about 200 nm to 2000 nm.

  As shown in FIG. 3, the core layer 21 includes a diffraction grating 29, reflection surfaces 211 and 212, and side surfaces 215 and 216. The reflecting surfaces 211 and 212 are deflecting units that deflect light combined by the diffraction grating 29 described later in the direction of the parabolic axis C described later, and the side surfaces 215 and 216 reflect the deflected light toward the focus F by reflection. It is formed so as to condense.

  The shape of the side surfaces 215 and 216 is a parabola, and as shown in FIG. 3, the center axis of symmetry is indicated by an axis C (a line perpendicular to the quasi-line (not shown) and passing through the focal point F). This is shown as a focal point F. The side surfaces 215 and 216 may be provided with a reflective material such as gold, silver, and aluminum to help reduce light reflection loss. Similarly, the reflective surfaces 211 and 212 may be provided with the above-described reflective material. Good.

  In addition, the core layer 21 of the waveguide includes a tip portion 24 having a planar shape in which the tip of a parabola adjacent to the disk 2 is cut. Since the light emitted from the focal point F spreads suddenly, it is preferable to make the shape of the front end portion 24 flat so that the focal point F can be arranged closer to the disc 2 and the focal point F is focused on the front end portion 24. May be formed.

  It is preferable to provide the probe 25 in the vicinity of the distal end portion 24. By irradiating the probe 25 with the light condensed at the focal point F, near-field light is generated as a minute light spot and the disk 2 can be irradiated.

  The diffraction grating 29 provided in the core layer 21 is parallel to the parabolic axis C in the shape of the side surfaces 215 and 216 provided in the core layer 21 and has a predetermined period in a direction perpendicular to the axis C. It is composed of a plurality of grooves. For example, the light 52 emitted from the light source 50 and collected using an optical system (not shown) composed of a spherical lens or the like enters the diffraction grating 29 perpendicularly (the incident angle to the diffraction grating 29 is zero). The diffraction grating 29 is irradiated.

  In FIG. 3, light that irradiates the diffraction grating 29 with light 52 is indicated by a light spot 55. The light spot 55 is coupled to the core layer 21 via the diffraction grating 29. Since the diffraction grating 29 has a simple configuration as described above, it can be easily manufactured using a known photolithography technique or etching process. Further, since there is no discontinuous portion of the diffraction grating in the region irradiated with the light spot 55, the irradiated light energy can be efficiently coupled to the core layer 21.

  A cross section of the diffraction grating 29 taken along a plane perpendicular to the parabolic axis C is schematically shown in FIG. In FIG. 6, the diffraction grating 29 is configured by a groove that is parallel to the parabolic axis C (perpendicular to the paper surface) and has a period Λ in the perpendicular direction to the axis C. As shown in FIG. 6, when the period Λ is appropriately set and light is incident (light 52) perpendicularly to the surface on which the diffraction grating 29 is formed, the + 1st order light 523 diffracted by the diffraction grating 29 is obtained. −1 order light 524 can be coupled to the core layer 21 and travel symmetrically. Since both ± first-order lights can be coupled to the core layer 21, the incident light 52 can be used efficiently. In addition, this is effective in realizing condensing that is strengthened by aligning the electric field vector with the probe 25 described later. Reference numeral 521 denotes transmitted light in which the irradiation light 52 is transmitted through the core layer 21 including the diffraction grating 29, and reference numeral 522 denotes reflected light that is reflected from the core layer 21 including the diffraction grating 29.

  When adjustment is made so that the incident light on the diffraction grating 29 is perpendicular to the light 52 emitted from the light source 50, setting in the direction perpendicular to the axis C is more preferable than setting in the direction along the axis C of the diffraction grating 29. But more accuracy is needed. The adjustment direction that requires higher accuracy is a direction that does not affect the flying characteristics of the slider 30 of the optical recording head 3, that is, a direction parallel to the recording surface of the disk 2. Adjustment to enable efficient vertical incidence can be easily performed.

For comparison, FIG. 7 shows a case where light is incident on the diffraction grating with a predetermined incident angle θ (θ> 0) with respect to the surface on which the diffraction grating is formed, and the light is coupled to the core layer. explain. When light incident on the diffraction grating 89 having a predetermined period Λ ₁ at a predetermined angle θ ₁ is coupled to the core layer 81, the + 1st order light 923 is compared with the + 1st order light 523 shown in FIG. However, since the −1st order light 924 cannot travel in the core layer 81 without traveling in the symmetric direction with the + 1st order light 923 and is not coupled to the waveguide. Loss. The relationship between the incident angle of the light that irradiates the diffraction grating and the optical coupling to the core layer will be further described later.

  3, 4, and 5, the light irradiated on the diffraction grating 29 becomes the + 1st order light 523 and the −1st order light 524 as shown in FIG. 6, and the core is perpendicular to the axis C. The light travels in combination with the layer 21 and enters the reflecting surfaces 211 and 212 which are deflecting portions for deflecting the optical path. The incident light is deflected in a direction parallel to the axis C by the reflecting surfaces 211 and 212 having an incident angle of 45 degrees. Light that is deflected and travels through the core layer 21 can be incident on and reflected from the side surfaces 215 and 216 to be focused at the focal point F.

  In FIG. 8, arrows E10 to E22 schematically represent instantaneous values of the electric field of light coupled to the core layer 21 by the diffraction grating 29 (however, the phase shift at the reflecting surfaces 211 and 212, the phase shift due to the optical path). Is the same as being symmetrical with respect to the axis C). The polarization of light incident on the diffraction grating 29 is assumed to be a TE wave. In FIG. 8, it is assumed that there is no physical length difference between the optical paths p1 and p2 from the light irradiation position P to the focal point F. The light spot 55 input perpendicularly to the diffraction grating 29 is evenly coupled to the mode propagating in the ± Y-axis direction, which is the direction perpendicular to the axis C. The ± first-order light propagating in the ± Y-axis direction is deflected by 90 degrees at the reflecting surfaces 211 and 212, proceeds, is incident and reflected from the side surfaces 215 and 216, and is collected at the focal point F.

  As shown in FIG. 8, the initial electric field vectors E10 and E20 of the light propagating in the ± Y-axis directions are symmetrical with respect to the bending directions of the reflecting surfaces 211 and 212 and the side surfaces 215 and 216, so The electric field vectors can be aligned at the focal point F. That is, the electric field vectors can be aligned in the long axis direction of the probe 25. Therefore, it is possible to realize the condensing that is strengthened by aligning the electric field vector in the long axis direction of the probe 25 with a simple configuration using one diffraction grating 29 without adjusting the phase difference between the optical paths p1 and p2. Field light can be generated.

  Instead of the mirrors shown as the reflecting surfaces 211 and 212 in FIG. 3, the reflecting portion is a reflecting structure 21A or 21B using a photonic band gap schematically shown in FIG. 9 or a waveguide with a periodic refractive index difference. It can also be realized as reflecting structures 21E and 21F using a grating. Each of the reflection structures 21A, 21B, 21E, and 21F shown in FIG. 9 includes a method of forming periodic holes and grooves, and the holes and grooves are formed using a known photolithography technique or etching process. It can be carried out.

  In addition, the diffraction grating 29 has a rectangular cross-sectional shape, but is not limited thereto, and may be a trapezoid, a sawtooth (blazed), or a sine wave.

  The relationship between the incident angle of the light that irradiates the diffraction grating and the optical coupling to the core layer will be described. FIG. 10A schematically shows, in a cross-sectional view, how incident light 102 incident on the diffraction grating 115 provided in the core layer 110 is optically coupled to the core layer 115, as in FIGS. 6 and 7. . FIG. 10B is an enlarged view of a part of the diffraction grating indicated by J in FIG. The diffraction grating 115 is formed with a concavo-convex grating having a period Λ. Light that irradiates the diffraction grating 115 is incident light having an incident angle θq, and light that is coupled to the core layer 110 and travels in the Y direction along the core layer 110 is q-order light 103 having a diffraction order of q.

When the wavelength lambda _o of the incident light is an example 1.5 [mu] m, _{n c,} for example the refractive index of air (1.0), _{n f} is the refractive index of the core layer _{(Si) (3.5), n} s is clad refractive index of the layer (SiO ₂₎ (1.44) can be mentioned. When incident light is in the visible light band, the core material Si has a large loss, so Ta ₂ O ₅ or the like is preferable in place of Si. As described above, in order to efficiently confine light in the waveguide, it is necessary to make the refractive index of the material forming the core layer larger than the refractive index of the material forming the cladding layer. If an equivalent refractive index to be described later of the waveguide is n _eff , the equivalent wavelength λ _eff in the waveguide is λ _eff = λ _o / n _eff . Here, λ _o is the wavelength in vacuum. As described above, when the light incident on the diffraction grating 115 can be coupled to the core layer 110, the incident angle θ _{q of the} light needs to satisfy the following formula (1) of the Bragg diffraction condition. Here, since n _c <n _eff , the coupling cannot be performed at an angle of q = 0.
n _eff × k _o = n _c × k _o × sin θ _q + q × K (q = 0, ± 1, ± 2,...) (1)
However,
K = 2 × π / Λ
k _o (wave number in vacuum) = 2 × π / λ _o
q is the diffraction order of the diffraction grating, and q = ± 1 is the main diffraction component. The diffraction efficiency when the value of q is larger than +1 or when the value of q is smaller than −1 is smaller than q = ± 1st-order diffraction efficiency. In order to increase the coupling efficiency, the diffraction grating period Λ may be set so that q = ± first-order light with good diffraction efficiency can be coupled into the core layer 110. In this case, the period Λ of the diffraction grating 115 is in a range of about 0.1 × λ _eff to 10 × λ _eff . Since θ _q = 0 at the time of normal incidence from equation (1),
n _eff × k _o = q × K (q = 0, ± 1, ± 2,...)
Therefore,
Λ = q × (λ _o / n _eff ) (q = 0, ± 1, ± 2,...) (2)
If the period Λ is made equal to λ _o / n _eff , the primary light can be coupled into the core layer 110.

In the case of horizontal incidence, the incident angle θ _q = 90 (°), so
n _eff × k _o −n _c × k _o = q × K (q = 0, ± 1, ± 2,...)
Therefore,
Λ = q × (λ _o / (n _eff −n _c )) (q = 0, ± 1, ± 2,...) (3)
Thus, if the period Λ is λ _o / (n _eff −n _c ), the primary light can be coupled into the core layer 110.

Here, with q = 1, a specific example will be given to explain the relationship between the incident angle θ ₁ to the diffraction grating 115 and the period Λ of the diffraction grating. In FIG. 10, the wavelength λ _o of the incident light 102 is 633 nm, n _c is the refractive index of air (1.0), n _f is the refractive index (2.09) of the core layer 110 (Ta ₂ O ₅ ), and n _s. Is the refractive index (1.47) of the cladding layer (SiO ₂ ), and the thickness t of the core layer 110 is 0.1 μm. As shown in FIG. 10, the diffraction grating 115 has a rectangular cross section, a concave shape with a period Λ and a depth Δ = 20 nm, and a duty ratio of the concaves and convexes of 50%.

At this time, the equivalent refractive index n _eff in the TE0th-order mode, which is polarized in parallel to the plane forming the waveguide that is the core layer 110, can be obtained as 1.61 by mode analysis. The mode analysis is described in the literature (K. Ogawa et al, “A Theoretical Analysis of Etched Grating Couplers for Integrated Optics,” IEEE J. Quantum Electron. 2, Vol. ).

FIG. 11 shows the relationship between the incident angle θ ₁ and the period Λ shown in the equation (1) in the configuration of FIG. As shown in FIG. 11, the incident angle θ ₁ can be set in the range of 0 to 90 degrees by changing the period Λ between λ _o / n _eff and λ _o / (n _eff −n _c ). . In FIG. 11, the period Λ is changed in the range of 0.6 × λ _o to 1.6 × λ _o , and when the period Λ is 0.6 × λ _o , light enters the diffraction grating 115 vertically (incident). The angle θ ₁ = 0) indicates that ± 1st order light can be optically coupled to the core layer 110. As described above with reference to FIG. 6, the propagation modes of the core layer 110 in the + Y and −Y directions are respectively shown. Evenly coupled light can be propagated.

  As described above, the light irradiated perpendicularly to the diffraction grating 29 is optically coupled to the core layer 21 of the waveguide as ± first-order light, and the coupled light is symmetric in the direction perpendicular to the parabolic axis C. After being deflected by the reflecting surface, the light travels parallel to the parabolic axis C, is incident on and reflected by the parabolic side surface, and can be condensed at the focal point F of the distal end portion 24 of the core layer 21. In addition, while having a simple configuration as described above, it is possible to irradiate the probe 25 with the electric field vectors aligned, and it is possible to efficiently generate near-field light. For this reason, the optical element 20 can emit light more efficiently than the tip portion 24 while having a small and simple configuration. By using this optical element 20, the optical recording head 3 and the optical recording with high optical efficiency can be obtained. Device 100 can be obtained.

  The optical recording head 3 described so far is an optically assisted magnetic recording head that uses light for information recording on the disk 2. However, the optical recording head 3 uses light for information recording on a recording medium, and the magnetic recording unit 40 or magnetic reproducing unit. For example, an optical recording head that performs recording such as near-field optical recording and phase change recording may be used.

It is a figure which shows the example of schematic structure of the optical recording device carrying an optically assisted magnetic recording head. 1 shows a cross-sectional view of an example of an optical recording head. It is a figure which shows the front view of a waveguide. It is a figure which shows the side view of a waveguide. It is a figure which shows the perspective view of a waveguide. It is a figure explaining a diffraction grating. It is a figure explaining the conventional diffraction grating. It is a figure explaining the electric field vector of the light condensed on a focus. It is a figure which shows the example of a deflection | deviation part. (A) is sectional drawing which shows typically a mode that the incident light which injects into a diffraction grating is optically coupled with a core layer. (B) is a figure which expands and shows a part of diffraction grating shown by J of (a). It is a figure which shows the relationship between the incident angle when the light which injects into a diffraction grating is optically coupled with an optical waveguide, and the period of a diffraction grating.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 2 Disk 3 Optical recording head 4 Suspension 5 Arm 20 Optical element 21 Core layer 211,212 Reflecting surface 215,216 Side surface 22 Clad layer 24 Tip part 25 Plasmon probe 29 Diffraction grating 30 Slider 32 ABS surface 40 Magnetic recording part 41 Magnetic reproducing unit 50 Light source 52 Light 523 + 1st order light 524 −1st order light 55 Optical spot 60 Near field light C axis F Focus P position p 1, p 2 Optical path

Claims (5)

A part of the contour shape is a parabola, a core layer having a flat tip portion, and a clad layer in contact with the core layer, the light coupled to the core layer is focused on the focal point of the parabola, An optical element from which light is emitted from the tip,
In the core layer,
A diffraction grating that introduces irradiated light into the core layer at a position where the core layer is irradiated with light, and couples the introduced light as light traveling in a direction perpendicular to the parabola axis;
A deflection unit coupled by the diffraction grating and deflecting light traveling in a direction perpendicular to the parabola axis in a direction parallel to the parabola axis;
The optical element, wherein the diffraction grating has a plurality of grooves formed in parallel with the parabolic axis at a predetermined period. The optical element according to claim 1, wherein a plasmon probe that generates near-field light by light irradiation is provided at a focal point of the parabola. The optical element according to claim 1 or 2,
An optical recording head comprising: a light source that irradiates light to the diffraction grating of the optical element. The optical recording head according to claim 3, further comprising a magnetic recording unit that performs magnetic recording on the magnetic recording medium. An optical recording head according to claim 4,
A magnetic recording medium;
An optical recording apparatus comprising: a control unit configured to perform magnetic recording on the magnetic recording medium by the optical recording head.

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