JP2009048742A - Optical head and information storing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical head structured to have a low mode order in a core, to be mounted on a slider, and manufactured by a lithography technique, and to provide an information storing apparatus having the optical head so as to record information with high recording density. <P>SOLUTION: The optical head comprises: a waveguide core for guiding light incident therein in its waveguide direction; an inclined core which is made of the same optical material as the waveguide core, which is connected to the waveguide core to be extended in the form of a layer in a direction tilted to the waveguide direction, and which guides light to the waveguide core; a cladding film which is overlapped with the layer of the inclined core and has a refractive index lower than the refractive index of the inclined core; and an incident core which is in contact with the cladding film, thicker than the inclined core and which guides incident light to the inclined core over the cladding film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical head that guides and emits light, and an information storage device that records information on a recording medium using light.

  In the field of information storage devices, the continuous improvement of recording density is required with the development of computers and IT. As a method to improve the recording density by recording finer bits than the current magnetic recording head, light is irradiated onto the recording medium, heat is locally generated on the medium, and writing with the magnetic head is performed by the heat. A heat-assisted recording system that facilitates the development is being studied. The spot size of light necessary for this heat-assisted recording is less than the diffraction limit achievable with a focused spot by a lens. Therefore, a head using an optical waveguide has been studied.

  FIG. 1 is a diagram showing an information storage device of a heat assist recording method.

  FIG. 1 shows the periphery of the head 40 of the information storage device 1. The information storage device 1 includes a disk-shaped information recording medium 10 that rotates in the direction of the arrow shown in the figure, and information that is recorded in the direction of magnetization, and an air flow that occurs on the surface of the rotating information recording medium 10. A slider 50 that floats from the surface in the state of being close to the surface of the information recording medium 10 and an arm 20 that extends along the surface of the information recording medium 10 and holds the slider 50 at the tip are provided. The slider 50 includes a slider body 30 that generates a floating force from the surface of the information recording medium 10, and a head 40 that performs information recording and information reproduction with respect to the information recording medium 10 is mounted on a side surface of the slider body 30. The head 40 records and reproduces information along an arc-shaped track on the information recording medium 10 as the information recording medium 10 rotates.

  The head 40 includes a reproducing head 41 that reproduces information by reading the direction of magnetization on the information recording medium 10, and a magnetic head 43 that records information by applying a magnetic field to the information recording medium 10 to change the direction of magnetization. And an optical head 42 that assists in changing the direction of magnetization by the magnetic head 43 by generating light by irradiating the information recording medium 10 with light. Although the illustration of the light source of the optical head 42 is omitted, a semiconductor laser is mounted, and light emitted from the semiconductor laser is guided to the optical head 42.

  The basic structure of the optical head 42 is a so-called optical waveguide, and the light incident from above in FIG. 1 is guided downward in FIG. 1 and emitted toward the information recording medium 10.

  At the front end (outgoing end) of the optical head 42, the light spot size must be reduced to a wavelength or less in each of the radial direction (intertrack direction) and the circumferential direction (track direction) of the information recording medium 10. The core size of the optical waveguide constituting the head 42 must also be less than the wavelength. In FIG. 1, the depth direction in the figure is the track-to-track direction, and the left-right direction in the figure is the track direction.

  However, if a semiconductor laser is used as the light source, the size of the light beam generated by the semiconductor laser is larger than the submicron, and therefore a structure for reducing the light beam inside the optical head 42 is required.

  Current magnetic recording heads that do not employ the heat-assisted recording method are manufactured by lithography technology that stacks materials on a substrate plane and performs pattern etching. This lithography technology has abundant technical accumulation and is reliable. Economical. Therefore, it is desirable that a new head that employs the heat-assisted recording method has a structure that can be manufactured by application of lithography technology. When the head 40 is manufactured by the lithography technique, the vertical direction and the depth direction in FIG. 1 are in-plane directions of the stack, and the horizontal direction in FIG. 1 is an interlayer direction of the stack.

  According to this lithographic technique, patterning in a plane has already been realized with a submicron width (that is, a size smaller than the wavelength of light) by an electron beam or a stepper device. Therefore, with respect to the core size in the track-to-track direction, the sub-micron width can be easily realized by etching the tapered pattern from several tens of microns to sub-microns. Further, the longer the taper length, the higher the light efficiency and the more light can be propagated to the narrow core. However, it is easy to produce such a long taper length.

  On the other hand, regarding the miniaturization of the core size in the track direction, considering that the taper is processed from the tens of micron size to the submicron similarly to the inter-track direction, a long tapered surface is produced in order to increase the light efficiency. In this case, a tapered surface having a large angle with respect to the normal of the substrate plane must be formed. However, in the lithography technique, it is difficult to produce such a tapered surface, and some contrivance is required.

  Therefore, conventionally, a method has been proposed in which a core is manufactured with a submicron thickness and light is incident on the core. In the field of optics, the incidence of light on such a core may be referred to as light coupling inside and outside the core. As typical proposals for the method of causing light to enter the core, an end face coupling method (see Non-Patent Document 1), a prism coupling method (see Non-Patent Document 2), and a grating method (see Non-Patent Document 3) are known. ing.

  FIG. 2 is an explanatory diagram of the end face coupling method.

  In FIG. 2 (and FIGS. 3 to 5 described later), a portion corresponding to the optical head 42 shown in FIG. 1 is shown. The upper side is the head side on the slider body side. The same applies to FIGS. 3 to 5 described below.

  The end face coupling method is a method in which a light beam L1 emitted from a light source is converted into convergent light using a lens 51 or the like and is incident on a core 53a exposed on a cut surface of the slider 52. The core 53a is sandwiched between the clads 53b, and the incident light propagates in the core 53a.

  FIG. 3 is an explanatory diagram of the prism coupling method.

  In the prism coupling method, the prism 55 is arranged with respect to the core 54 of the optical waveguide constituting the optical head, and an interval equal to or smaller than the wavelength of the light is provided between the core 54 and the bottom surface of the prism 55 so that the phase of the light impinging on the bottom surface of the prism 55 is reduced. In this method, the bottom surface is irradiated with light at a predetermined incident angle θ so that the phase of the propagation light in the core 54 is the same. In order to obtain such an incident angle θ, an inclined surface 55 a is formed on the incident side of the prism 55.

  FIG. 4 is an explanatory diagram of the grating method.

The grating method is a method in which a grating 57 is formed on the upper surface of the core 56, and light is coupled using a diffraction angle in which the phase of propagating light in the core 56 and the phase of light incident on the grating 57 are the same.
Shubert, R.A. Harris, J.M. H. , “Optical Surface Waves on Thin Films and Theair Application to Integrated Data Processors”, IEEE Trans. Microwave Theory and Tech. , 16, 12, pp. 1048-1054, Dec. 1968 (ISSN: 0018-9480) J. et al. H. Harris, R.D. Shubert, and J.M. N. Polky, "Beam Coupling to Films," J. et al. Opt. Soc. Am. 60, p1007 (1970) (ISSN: 0030-3941) M.M. L. Dakss, L.M. Kuhn, P.A. F. Heidrich, and B.B. A. Scott, “GRATING COUPLER FOR EFFICENT EXCITATION OF OPTICAL GUIDED WAVES IN THIN FILMS”, Appl. Phys, Lett. , 16, 12, pp. 523-525, June 1970 (ISSN: 0003-6951)

  Since the above prism coupling method has a drawback in terms of ease of fabrication as will be described later, it can be considered that the prism coupling method is changed to a structure that can be fabricated by a lithography technique. In the present specification, the coupling method (method of entering light into the core) with the structure changed in this way is referred to as a taper coupling method.

  FIG. 5 is an explanatory diagram of the taper coupling method.

  In the taper coupling method, instead of the prism in the prism coupling method, a thick first core 58 that can be manufactured by a lithography technique is used, and light is incident on a second core 59 having a submicron thickness at the same incident angle θ as in the prism coupling method. It is a method to make it.

  The end face on the incident side of the first core 58 is perpendicular to the incident light, and light reflection at the inclined surface 58a of the first core 58 is used in the taper coupling method in order to obtain the incident angle θ described above.

  In the case of an optical head used for the heat-assisted recording method, it is necessary to consider the mode of light after incidence in any of the coupling methods described above.

  FIG. 6 is a schematic diagram showing the electric field intensity distribution of mode light.

  The vertical axis in the figure represents the position in the core in the direction crossing the light propagation direction, and the horizontal axis in the figure represents the electric field strength of light at each position.

  The electric field intensity distribution of the mode light has a distribution of one mountain in the basic mode, but two distributions in the primary mode and three distributions in the secondary mode.

  In the case of an optical head used for the heat-assisted recording method, the fundamental mode showing the intensity distribution of one mountain is more effective than the higher-order mode light if the output intensity is the same. This is because, if the intensity distribution is one mountain, the peak intensity of light when irradiating the information recording medium can be strengthened, and the temperature on the information recording medium can be locally increased.

  Considering such a mode of light, each coupling method described above will be examined below.

First, in the end face coupling method, the core exposed to the cut surface of the slider is irradiated with convergent light. At this time, the fundamental mode light can be generated in the core by reducing the NA of the convergent light. In addition, since light is irradiated onto the cut surface of the slider, there is an advantage that it does not overlap with the electrode pads for writing and reading necessary for the magnetic head and the reproducing head. However, if the NA is reduced to generate the fundamental mode, the spot size of the convergent light at the end face on the incident side of the slider is increased. For example, when a 660 nm laser is irradiated onto an optical waveguide having a core material of TiO ₂ , a core thickness of 0.6 μm, and a cladding material of Al ₂ O ₃ , the NA that generates the fundamental mode is 0.48. is there. The spot size obtained by this NA is 1.2 μm, which is larger than the core thickness, so that the amount of light incident on the core decreases. Conversely, when the laser is focused so that the spot size is about 0.6 μm (wavelength), which is the diffraction limit, NA is 0.9 or more, and high-order mode light is generated in the core and propagated light. There is a problem in that the intensity distribution characteristics of the material deteriorate.

  Next, in the prism coupling method, mode light is excited by phase matching between the incident light and the guided mode in the core with a low refractive index thin layer (usually air) in between, so even if the core thickness is less than the wavelength Light coupling is possible. However, in order to generate the fundamental mode, the incident angle θ with respect to the bottom surface of the prism must be increased. If the incident angle θ is small, higher-order mode light is generated. For example, in order to realize coupling to a core having a thickness of 0.4 μm, although depending on the refractive index of the prism, the incident angle θ needs to be a large angle of 80 to 85 degrees or more. Thus, when the incident angle θ is large, the total reflection area on the bottom surface of the prism increases to 1 / cos θ times the beam diameter. Therefore, there is a problem that the propagation light coupled to the core returns to the prism bottom side again and the coupling efficiency is lowered. When focusing to reduce the light beam diameter, a difference occurs in the inclination of the light beam in the light beam, and a difference occurs in the incident angle to the prism bottom surface, so that the spot area where phase matching with the core is realized is limited. Coupling efficiency decreases. Furthermore, since the surface on which the prism is mounted is the same surface as the electrode pad for writing and reading, a sub-millimeter size prism is required for mounting on the slider, but such a small size prism is used alone. There is a problem that it is difficult and expensive to manufacture.

  Unlike the prism method, the grating method produces the grating in the plane of the substrate, so there is a problem that it is mounted on the same surface as the electrode pad for writing and reading. There is an advantage that you can. However, in order to improve the coupling efficiency in the grating, the spot size irradiated on the grating must be increased. From an optical theory, the coupling efficiency gradually approaches 1 when the spot size is increased infinitely. However, of course, the grating fabrication area must be finite in size and must be sub-millimeter size to be mounted on the slider, resulting in reduced coupling efficiency. In addition, the grating lattice has a submicron spacing, and the coupling efficiency is lowered due to variations in the depth and width of the spacing, making it difficult to manufacture.

  In the taper coupling method, the incident angle θ of the light beam is given by reflection by an inclined surface, and the end surface on the incident side is perpendicular to the incident light. This structure is adopted from the viewpoint of mass production processing, and is adopted because it is difficult to produce an inclined surface on the end face on the incident side as in the prism coupling method. Similarly to the prism coupling method, the incident angle θ must be increased to excite the fundamental mode in the core. That is, the inclination angle α of the inclined surface 58a shown in FIG. 5 must be reduced. However, it is difficult to reduce the inclination angle α in etching and cutting, and if an inclination angle α that is realistic in production is used, Has the problem that higher modes are excited.

  FIG. 7 is a diagram showing the electric field strength distribution when using an inclination angle α that is realistic in production.

In FIG. 7, the core material is TiO ₂ , the clad material is Al ₂ O ₃ , the first core thickness is 5 μm, the second core thickness is 0.7 μm, the first core and the second core As a result of calculating the electric field intensity distribution when the intermediate clad between them is 0.1 μm, the inclination angle α of the taper surface is 21.2 degrees, and the wavelength of the laser is 660 nm, a portion P where the electric field intensity is high is shown. Even when the inclination angle α is as small as 21.2 degrees, the third-order mode light L2 is excited in the second core as shown in FIG. In order to excite fundamental mode light, the inclination angle must be 10 degrees or less, and it is difficult to process a core of several microns thickness at such an inclination angle in industrial mass production.

  In view of the above circumstances, the present invention provides an optical head having a structure in which the mode order in the core is low, can be mounted on a slider, and can be manufactured by a lithography technique, and such an optical head is provided. An object is to provide an information storage device capable of recording information at a recording density.

The optical head of the present invention that achieves the above object provides:
An optical head that receives light from the outside, finally guides the incident light along a predetermined waveguide direction, and emits the light from the tip.
A waveguide core made of a predetermined optical material, extending in a layered manner along the waveguide direction, and in which light is incident and guides the light in the waveguide direction;
It is made of the same optical material as that constituting the waveguide core, and is connected to the waveguide core on the incident side of light guided to the waveguide core and extends in a layered manner in a direction inclined with respect to the waveguide direction. A tilted core in which light is incident and guides the light to the waveguide core;
A clad film made of an optical material having a refractive index lower than the refractive index of the optical material constituting the inclined core, which overlaps the layer of the inclined core;
Made of an optical material that is in contact with the cladding film and has a refractive index higher than the refractive index of the optical material that constitutes the cladding film, which is thicker than the thickness of the inclined core. And an incident core that is incident on the inclined core.

  Although this clad layer may be zero in thickness, it is desirable for the thickness to be equal to or less than the wavelength within the clad layer of incident light.

  According to the optical head of the present invention, the light incident on the incident core is incident on the inclined core by the coupling of light. At this time, the incident angle necessary for phase matching is the same as the incident angle in the prism coupling method described above, but in the present invention, the mode order can be lowered when light is guided from the inclined core to the waveguide core. . For this reason, even if the tilt angle of the tilt core is a realistic angle that is large enough to be produced by lithography technology, the mode light finally excited in the waveguide core is the low-order mode light. Become. In addition, the optical head of the present invention can be manufactured so as to be within a size that can be mounted on the slider because the tilt angle of the tilt core can be sufficiently increased. Furthermore, since the thickness of the incident core can be sufficiently increased, the amount of incident light from the outside into the optical head can be sufficiently increased to improve the light utilization efficiency.

In the optical head of the present invention,
The waveguide core and the incident core are formed on a lower clad having a refractive index lower than the refractive index of any optical material constituting the waveguide core and the incident core,
Between the lower clad and the waveguide core and the incident core, there is a protective film whose etching property in a predetermined reactive etching is lower than that of the waveguide core and the incident core. ''
Is a preferred form.

  According to this preferred form of the optical head, even when the inclination of the inclined core is processed by etching, the lower clad is protected by the protective film. can do.

  In the optical head of the present invention, it is preferable that the waveguide core has a tapered portion in which the spread of the layer becomes narrower toward the front in the waveguide direction.

  By having such a tapered portion, light propagating in the waveguide core is collected, so that it is possible to reduce the spot size and improve the intensity of the light emitted from the optical head.

  In the optical head according to the aspect of the invention, it is preferable that the inclined core has a convexly curved layer on the side opposite to the incident core side.

  Since the inclined core is curved in this way, light incident from the incident core to the inclined core is reflected by the curved surface and collected. The condensing position can be adjusted by adjusting the magnitude of the curvature of the inclined core, and the spot size can be reduced and the intensity of the emitted light from the optical head can be reduced.

The information storage device of the present invention that achieves the above object provides:
An optical head that receives light, finally guides the incident light along a predetermined waveguide direction, emits the light from the tip, and heats the surface of the recording medium with the light;
A magnetic head for recording information on the recording medium by applying a magnetic field to the surface of the recording medium heated by the optical head,
The optical head is
A waveguide core made of a predetermined optical material, extending in a layered manner along the waveguide direction, and in which light is incident and guides the light in the waveguide direction;
It is made of the same optical material as that constituting the waveguide core, and is connected to the waveguide core on the incident side of light guided to the waveguide core and extends in a layered manner in a direction inclined with respect to the waveguide direction. A tilted core in which light is incident and guides the light to the waveguide core;
A clad film made of an optical material having a refractive index lower than the refractive index of the optical material constituting the inclined core, which overlaps the layer of the inclined core;
Made of an optical material that is in contact with the cladding film and has a refractive index higher than the refractive index of the optical material that constitutes the cladding film, which is thicker than the thickness of the inclined core. And an incident core that is incident on the inclined core.

  According to the information storage device of the present invention, it is possible to irradiate the surface of the recording medium with low-order mode light by the optical head, and it is possible to record information at a high recording density by locally heating the surface of the recording medium. .

  As described above, the optical head of the present invention has a structure in which the mode order in the core is low and can be mounted on a slider and can be manufactured by a lithography technique. The information storage device of the present invention can record information at a high recording density.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 8 is a diagram showing a first embodiment of the information storage device of the present invention.

  FIG. 8 shows the periphery of the head 140 of the information storage device 100 as in FIG. The information storage device 100 shown in FIG. 8 is a heat-assisted recording type information storage device, and the structure of other parts other than the part shown in FIG. 8 is a well-known structure in the information storage device. Since it is the same structure, description is abbreviate | omitted. The basic structure of the information storage device 100 shown in FIG. 8 is the same as the basic structure of the information storage device 1 shown in FIG. 1, and is a disc-shaped information recording medium that rotates in the direction of the arrow shown in the figure. 110, a slider 150 that floats from the surface in the state of being close to the surface of the information recording medium 110, and an arm 120 that extends along the surface of the information recording medium 110 and holds the slider 150 at the tip.

  The slider 150 has a configuration in which a head 140 is mounted on a slider main body 130, and the head 140 includes a reproducing head 141, an optical head 142, and a magnetic head 143. Here, the optical head 142 corresponds to the first embodiment of the optical head of the present invention.

  Although the illustration of the light source of the optical head 142 is omitted here, a semiconductor laser is mounted on the information storage device 100, and the light emitted from the semiconductor laser is an optical waveguide having a thickness of several tens of microns. The structure is guided to the optical head 142.

  Next, the structure of the optical head 142 will be described.

  FIG. 9 is a cross-sectional view of the optical head, and FIG. 10 is a perspective view of the optical head. However, FIG. 9 shows the structure of the optical head mainly on the light incident side, and FIG. 10 mainly shows the core portion of the waveguide constituting the optical head. 9 and 10, the optical head is shown in a direction in which the light guiding direction is the horizontal direction in the drawing, for convenience of illustration. In the following description, the vertical direction in FIG.

  The optical head 142 of this embodiment is formed on the upper shield 204 of the reproducing head 141, and a lower clad 1421 having a low refractive index exists on the upper shield 204, and a protective film 1422 is formed on the lower clad 1421. Is provided. On the protective film 1422, the first core 1423 having an inclined surface and a micron-sized thickness and a high refractive index is present. The inclined surface of the first core 1423 is covered with a thin intermediate clad 1424 having a low refractive index, and the refractive index of the intermediate clad 1424 is smaller than the first core 1423 in a submicron size. A high second core 1425 is provided. The second core 1425 has an inclined portion 1425a along the inclined surface of the first core 1423, and an extended portion 1425b connected to the inclined portion 1425a and extending on the protective film 1422. The extended portion 1425b is As shown in FIG. 10, the taper has a tapered shape. The uppermost portion of the optical head 142 is covered with an upper clad 1426 having a low refractive index.

  The first core 1423 corresponds to an example of the incident core referred to in the present invention, the intermediate cladding 1424 corresponds to an example of the cladding film referred to in the present invention, and the extended portion 1425b of the second core 1425 refers to the conductor referred to in the present invention. It corresponds to an example of a wave core, and the inclined portion 1425a of the second core 1425 corresponds to an example of an inclined core according to the present invention.

As a material of the lower cladding 1421, the intermediate cladding 1424, and the upper cladding 1426, Al ₂ O ₃ or SiO ₂ can be used. As a material of the first core 1423 and the second core 1425, for example, TiO ₂ can be used. it can. Further, the protective film 1422 is for protecting the lower clad when the first core 1423 is processed by etching as will be described later, and a material corresponding to the type of reaction gas used in the etching can be used. Depending on the material, a film thickness of several tens of nm or less is sufficiently effective. For example, in the case of etching using CF ₄ reactive gas, it can be formed of a fluorine-based material such as MgF ₂ .

  The light L3 from the light source is incident on the optical head 142 having such a structure from the left side of the drawing, propagates through the first core 1423, and is irradiated onto the inclined surface of the first core 1423 at a predetermined incident angle θ. . Then, the light in the first core 1423 and the light in the inclined portion 1425a of the second core 1425 are combined by phase matching on the inclined surface, and the light is efficiently introduced into the second core 1425. When the inclination angle α of the inclined surface is a sufficiently large angle that can be adapted to industrial mass production, the light introduced from the inclined surface of the first core 1423 into the second core 1425 becomes higher-order mode light. However, when the higher-order mode light is propagated through the second core 1425 and the propagation direction is changed at the end of the inclined portion 1425a, the light is converted into lower-order mode light and travels through the extended portion 1425b. In this embodiment, the extended portion 1425b of the second core 1425 is tapered in a tapered shape as shown in FIG. 10, and the low-order mode light propagating in the extended portion 1425b is inside the extended portion 1425b due to the tapered shape. The light is condensed while being reflected, and the medium is efficiently irradiated with strong light from the tip 142a of the optical head 142. In the present embodiment, a tapered tapered structure is employed as an example, but even if an elliptical or parabolic tapered structure is employed, light can be condensed.

  FIG. 11 is a diagram showing the electric field strength distribution in the optical head having the structure shown in FIGS. 9 and 10.

Here, the result of calculating the electric field intensity distribution using the FDTD method is shown, and the material of the first core and the second core is TiO _2, and the material of the lower cladding, the intermediate cladding, and the upper cladding is Al ₂ O _3. The protective film was omitted for simplicity of calculation. Further, the thickness of the first core is 10 μm, the thickness of the second core is 0.7 μm, the thickness of the intermediate cladding is 0.1 μm, the inclination angle α of the inclined surface of the first core is 38.5 degrees, the incident light Was calculated as a laser with a wavelength of 660 nm.

  FIG. 11 shows a point P where the electric field strength is strong as a result of the calculation. The third-order mode light L3_1 is once excited in the inclined portion of the second core and bent in the propagation direction in the second core. Thus, the intensity distribution mainly represents that the fundamental mode light L3_2 is excited. In other words, when the optical head structure as shown in the present embodiment is used, light can be efficiently excited into the optical head with low-order mode light even at a sufficiently large inclination angle α such as 38.5 degrees. it can.

Moreover, in the calculation shown here, a structure in which the protective film is omitted is used for the sake of simplicity, but since the smoothness of the lower cladding is maintained when the protective film is present, the lower cladding, the intermediate cladding, As the material of the upper clad, for example, SiO ₂ etched by a reactive gas can be used. As a result, the refractive index difference between the core and the clad increases and the total reflection angle decreases, so that the light propagation efficiency in the core is high, and in particular, the propagation efficiency when the propagation direction is bent in the second core is improved. . Further, when the total reflection angle is reduced, the inclination angle α of the inclined surface can be further increased, so that the workability is improved. Conversely, when Al ₂ O ₃ is used as the material of the lower cladding, the intermediate cladding, and the upper cladding, and TiO ₂ is used as the material of the first core and the second core, the etching property of Al ₂ O ₃ is TiO 2. _Since it is much lower than the etching property of ₂ , it is possible to omit the protective film.

In the calculation shown here, the same material as the other cladding is used as the material of the intermediate cladding, but the refractive index lower than the refractive index of the first core or the second core is used as the intermediate cladding material. When a fluorine-based material such as an MgF ₂ material having a rate is used, etching other than the second core due to the CF ₄ reactive gas can be suppressed.

  Next, a second embodiment of the information storage device of the present invention will be described. The information storage device of the second embodiment is the same device as the information storage device of the first embodiment described above except that the second embodiment of the optical head is mounted. A second embodiment will be described. The optical head of the second embodiment has substantially the same configuration as the optical head of the first embodiment described above except that the shape of the second core is different. The following description will be given focusing on the shape.

  FIG. 12 is a perspective view of the optical head of the second embodiment.

  In FIG. 12, as in FIG. 10, the core portion of the waveguide constituting the optical head is mainly shown.

  In the optical head 242 of the second embodiment, the inclined surface of the first core 2423 is convexly curved toward the tip 242a side of the optical head 242 and is a thin-film intermediate clad (not shown) similar to the first embodiment. ), A second core 2425 is formed along the inclined surface. For this reason, the inclined portion 2425a along the inclined surface of the second core 2425 is also curved convexly toward the tip 242a side. Further, in the optical head 242 of the second embodiment, the extended portion 2425b extending from the end of the inclined portion 2425a has a rectangular shape unlike the first embodiment. Therefore, in the optical head 242 of the second embodiment, there is no light collecting effect due to the shape of the extended portion 2425b, but the inclined surface of the first core 2423 and the inclined portion 2425a of the second core 2425 are curved. The light L4 incident on the optical head 242 is reflected and propagated by the inclined surface or the inclined portion 2425a to be condensed toward the center of the second core 2425. The slope of the inclined surface and the inclined portion 2425a and the length of the extended portion 2425b are designed geometrically so that the light transmitted through the extended portion 2425b is best collected at the end of the extended portion 2425b. Strong light is efficiently emitted from the tip 242a of the optical head 242.

  In the second embodiment, a rectangular shape is adopted as the shape of the extended portion 2425b in order to clearly show the light collecting effect due to the curved surface and the curved portion 2425a. The converging structure as in the embodiment may be used in combination, and both the condensing by the curved surface such as the inclined surface and the condensing by the tapered structure of the extended portion may be used.

  In each of the embodiments described above, the first core is provided below the inclined portion of the second core, and the traveling direction of the light incident on the optical head is substantially the same as the tip direction of the optical head. However, the first core referred to in the present invention may be provided above the inclined portion of the second core, and in an optical head having such a first core, the light enters the optical head. The traveling direction of light is a direction that is greatly inclined with respect to the tip direction of the optical head (in FIG. 9, a direction that enters from above with an angle that is approximately twice the inclination angle α).

  Below, the manufacturing method of the structure of each embodiment mentioned above is demonstrated.

  As described above, the slider 150 of the information storage device 100 shown in FIG. 8 has a configuration in which the head 140 is mounted on the slider main body 130, and the slider 150 having such a configuration is basically manufactured by a lithography technique. The process is well known in the art. That is, (1) a step of preparing a substrate on which a large number of slider bodies 130 are based, (2) a step of creating a large number of reproducing heads 141 on the substrate, and (3) an optical head on each reproducing head 141 142, (4) a step of creating a recording head 143 on each optical head 142, and (5) cutting out each head 140 together with the substrate and processing the substrate portion into the slider main body 130 to move the slider 150. It is a process to complete. Of these steps, the steps other than the step of creating the optical head 142 are the same as those in the prior art, so that further explanation is omitted, and the step of creating the optical head 142 will be described in detail below.

  FIG. 13 to FIG. 24 are process diagrams showing an example of a manufacturing method of the optical head according to the first embodiment. Each process diagram includes a side view (A) and a top view (B). Further, for the convenience of explanation, in each process diagram, only one of the optical heads that are created simultaneously is shown.

  FIG. 13 shows a state where the reproducing head 141 is formed on the substrate 201, and the reproducing head 141 has a structure in which the reproducing element 203 is sandwiched between the lower shield 202 and the upper shield 204. The optical head is formed on the upper shield 204.

As shown in FIG. 14, on the upper shield 204, an SiO ₂ lower clad film 205, an MgF ₂ protective film 206, and an optical head first layer are sequentially formed on the upper shield 204 by an ion plating method or the like. A first core film 207 of TiO ₂ to be processed into one core is formed.

  Next, in order to process the first core film 207 into the shape of the first core 1423 shown in FIG. 9, the shape of the upper surface of the first core 1423 is formed on the first core film 207 as shown in FIG. A resist pattern 208 is formed in an equivalent shape by a stepper device or the like. However, in FIG. 9, the right side of the figure is the tip side of the optical head, whereas in FIG. 15, the left side of the figure is the tip side of the optical head. Therefore, the reproducing element 203 of the reproducing head is formed at a position according to the left side of FIG. 15 and the resist pattern 208 is formed at the right end.

Next, the substrate 201 is set in the RIE apparatus at an angle of 50 to 70 degrees with respect to the reaction electrode, and reactive etching is performed obliquely using the resist pattern 208 as a mask as shown in FIG. As a reactive gas in this reactive etching, here, CF ₄ gas is used as an example. This gas reacts with TiO ₂ , but does not react with the protective film 206 of MgF ₂ , so that the first core film 207 is processed into a trapezoidal shape to form the first core 1423 shown in FIG. The presence of the protective film 206 protects the lower cladding film 205 of SiO ₂ that reacts with CF ₄ gas, and maintains smoothness. After the processing of the first core film 207, the resist pattern 208 is removed, and the trapezoidal first core film 207 (that is, the first core 1423) is exposed as shown in FIG.

Next, as shown in FIG. 18, on the first core film 207 and the protective film 206, an SiO ₂ intermediate clad film 209 serving as an intermediate clad of the optical head, and TiO processed into the second core of the optical head. _{A second} second core film 210 is formed. Then, in order to process the second core film 210 into the shape of the second core 1425 shown in FIG. 10, as shown in FIG. 19, a resist pattern 211 having a tapered shape similar to the shape of the second core 1425 is formed as a stepper device or the like. Is formed on the second core film 210. At this time, the tapered shape of the resist pattern 211 (that is, the shape of the extended portion of the second core) is designed so that light is efficiently collected at a position corresponding to the reproducing element 203, and corresponds to the reproducing element 203. A resist pattern 211 is formed at a predetermined position in the design.

Next, the substrate 201 is set in the RIE apparatus perpendicularly to the reaction electrode, and as shown in FIG. 20, the resist pattern 211 is used as a mask to perform reactive etching with CF ₄ gas perpendicularly. Since the CF ₄ gas reacts with TiO ₂ and SiO ₂ , the intermediate cladding film 209 and the second core film 210 are processed into a tapered shape similar to the resist pattern 211, and the shape of the second core 1425 shown in FIG. As described above, since the smoothness of the lower clad film 205 is maintained by the protective film 206, the angle between the inclined portion and the extended portion of the second core 1425 can be obtained with high accuracy, and between the inclined portion and the extended portion. The efficiency of light propagation and light mode conversion is high.

After the second core film 210 is processed in this manner, the resist pattern 211 is removed to expose the tapered second core film 210 (that is, the second core 1425) as shown in FIG. Then, as shown in FIG. 22, the structure of the above-described first embodiment of the optical head is completed by forming a SiO ₂ upper clad film 212 as the upper clad of the optical head as a whole.

  After the optical head is formed in this manner, a recording head 143 is formed on the upper cladding film 212 of the optical head as shown in FIG. Then, as shown in FIG. 24, the structure of the head 140 shown in FIG. 8 is completed by cutting out at the position of the reproducing element 203 and finishing to an accurate size by polishing.

  FIGS. 25 to 32 are process diagrams showing an example of a method of manufacturing the optical head according to the second embodiment. These process diagrams also include a side view (A) and a top view (B), and are easy to explain. For this reason, in each process drawing, only one of the optical heads produced at the same time is shown.

  Since the manufacturing method example of the optical head according to the second embodiment includes substantially the same steps as those in the manufacturing method example according to the first embodiment described above, the following is different from the manufacturing method example according to the first embodiment. This will be explained with a focus on.

  As shown in FIG. 25, in order to form up to the first core film 207 and process the first core film 207 into the shape of the first core 2423 shown in FIG. A resist pattern 213 is formed on the one core film 207 in a shape equivalent to the shape of the upper surface of the first core 2423. In the second embodiment, since the inclined surface of the first core 2423 is curved, the edge of the resist pattern 213 is rounded.

  Next, the substrate 201 is set in the RIE apparatus at an angle of 50 to 70 degrees with respect to the reaction electrode, and reactive etching is performed obliquely using the resist pattern 213 as a mask as shown in FIG. As a result, the first core film 207 is processed into a trapezoidal shape, and the inclined surface becomes a curved surface to form the first core 2423 shown in FIG. After the processing of the first core film 207, the resist pattern 213 is removed, and the trapezoidal first core film 207 (that is, the first core 2423) is exposed as shown in FIG.

Next, as shown in FIG. 28, on the first core film 207 and the protective film 206, an SiO ₂ intermediate clad film 214 serving as an intermediate clad of the optical head, and TiO processed into the second core of the optical head. _Second second core film 215 is formed. Then, as shown in FIG. 29, a rectangular resist pattern 216 similar to the shape of the second core 2425 is formed on the second core film 215 with a stepper device or the like.

Next, the substrate 201 is set in the RIE apparatus perpendicularly to the reaction electrode, and as shown in FIG. 30, the resist pattern 216 is used as a mask to perform the reactive etching perpendicularly with CF ₄ gas and the intermediate cladding film 214 and the second core. The film 215 is processed into a rectangular shape similar to the resist pattern 216. Thereby, the shape of the 2nd core 2425 shown in FIG. 12 is made.

After the second core film 215 is processed in this way, the resist pattern 216 is removed to expose the rectangular second core film 215 (that is, the second core 2425) as shown in FIG. Then, as shown in FIG. 32, the structure of the optical head 242 of the second embodiment shown in FIG. 12 is completed by forming a SiO ₂ upper clad film 217 as the entire upper clad of the optical head.

  In the third embodiment, in the first and second embodiments, the reproducing head side is flat, the recording core side has an incident core, and the inclined core is inclined to the magnetic head side, as shown in FIG. In addition, even if the recording head side is flat and the reproducing core side has an incident core, and the inclined core is inclined to the reproducing head side, the same effect can be obtained. In the manufacturing method of this embodiment, after the reproduction head 141 is manufactured, the reversal pattern of the first and second embodiments is etched on the reproduction head 141. Then, the lower clad film 205, the second core film 215, the intermediate clad 214, and the first core film 207 are sequentially formed. Then, after the first core is flattened, an upper clad film 217 is formed.

The fourth embodiment is an optical head in which the thickness of the intermediate cladding layer 214 is zero in the first, second, and third embodiments as shown in FIG. 34, and the refractive index of the second core film 215 is the first core. It is larger than the film 207. This manufacturing method can be manufactured by omitting the formation of the intermediate cladding layer in the manufacturing methods of the first, second, and third embodiments. In this embodiment, the first core film 207 of TiO ₂ processed into the first core of the optical head and the Si film 215 processed into the second core film are formed.

  When the first core film 207 and the second core film 215 are made of the same material, the first core film 207 and the second core film 215 become an optical waveguide that changes the core diameter, and can be approximated by making the inclined surface stepped.

It is a figure which shows the information storage apparatus of a heat assist recording system. It is explanatory drawing of an end surface coupling | bonding method. It is explanatory drawing of a prism coupling method. It is explanatory drawing of a grating method. It is explanatory drawing of a taper coupling method. It is a schematic diagram showing the electric field strength distribution of mode light. It is a figure showing electric field strength distribution when using a realistic inclination angle α. It is a figure which shows 1st Embodiment of the information storage device of this invention. It is sectional drawing of the optical head of 1st Embodiment. It is a perspective view of the optical head of 1st Embodiment. It is a figure showing electric field strength distribution in the optical head of the structure shown in FIG. 9 and FIG. It is a perspective view of the optical head of 2nd Embodiment. It is a 1st process drawing showing the example of a manufacturing method of a 1st embodiment. It is a 2nd process drawing showing the example of a manufacturing method of 1st Embodiment. It is a 3rd process drawing showing the example of a manufacturing method of a 1st embodiment. It is a 4th process drawing showing the example of a manufacturing method of a 1st embodiment. It is a 5th process drawing showing the example of a manufacturing method of a 1st embodiment. It is a 6th process drawing showing the example of a manufacturing method of a 1st embodiment. It is a 7th process drawing showing the example of a manufacturing method of a 1st embodiment. It is an 8th process drawing showing the example of a manufacturing method of a 1st embodiment. It is a 9th process drawing showing the example of a manufacturing method of a 1st embodiment. It is a 10th process figure showing the example of a manufacturing method of a 1st embodiment. It is an 11th process drawing showing the example of a manufacturing method of a 1st embodiment. It is a 12th process drawing showing the example of a manufacturing method of a 1st embodiment. It is a 1st process drawing showing the example of a manufacturing method of a 2nd embodiment. It is a 2nd process drawing showing the example of a manufacturing method of 2nd Embodiment. It is a 3rd process drawing showing the example of a manufacturing method of a 2nd embodiment. It is a 4th process drawing showing the example of a manufacturing method of a 2nd embodiment. It is 5th process drawing showing the example of a manufacturing method of 2nd Embodiment. It is a 6th process drawing showing the example of a manufacturing method of a 2nd embodiment. It is a 7th process drawing showing the example of a manufacturing method of a 2nd embodiment. It is an 8th process drawing showing the example of a manufacturing method of a 2nd embodiment. In 1st and 2nd embodiment, it is a figure of 3rd Embodiment which has an incident core in the read head side. In 1st, 2nd and 3rd embodiment, it is a form figure of 4th Embodiment whose thickness of an intermediate | middle cladding is zero.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Information storage device 110 Information recording medium 120 Arm 130 Slider main body 140 Head 141 Playback head 142 Optical head 143 Magnetic head 1421 Lower clad 1422 Protective film 1423 First core 1424 Intermediate clad 1425 Second core 1425a Inclined portion 1425b Extended portion 1426 Upper clad

Claims (7)

An optical head that receives light from the outside, finally guides the incident light along a predetermined waveguide direction, and emits the light from the tip.
A waveguide core made of a predetermined optical material, which extends in a layered manner along the waveguide direction, and in which light is incident and guides the light in the waveguide direction;
It is made of the same optical material as the optical material constituting the waveguide core, and is connected to the waveguide core on the incident side of light guided to the waveguide core and extends in a layered direction in a direction inclined with respect to the waveguide direction. An inclined core that receives light therein and guides the light to the waveguide core;
A clad film made of an optical material having a refractive index lower than the refractive index of the optical material constituting the inclined core, overlapping the inclined core layer;
The clad film is made of an optical material having a refractive index higher than the refractive index of the optical material constituting the clad film, which is in contact with the clad film and is thicker than the inclined core. An optical head comprising an incident core that is incident on the inclined core. The waveguide core and the incident core are formed on a lower clad having a refractive index lower than the refractive index of any optical material constituting the waveguide core and the incident core,
A protective film is provided between the lower clad and the waveguide core and the incident core. The protective film has an etching property in a predetermined reactive etching lower than that of the waveguide core and the incident core. The optical head according to claim 1.   The optical head according to claim 1, wherein the waveguide core has a tapered portion in which the spread of the layer becomes narrower toward the front in the waveguide direction.   3. The optical head according to claim 1, wherein the inclined core has a layer that is convexly convex on the side opposite to the incident core side. 4. An optical head that receives light, finally guides the incident light along a predetermined waveguide direction, emits the light from the tip, and heats the surface of the recording medium with the light;
A magnetic head for recording information on the recording medium by applying a magnetic field to the surface of the recording medium heated by the optical head,
The optical head is
A waveguide core made of a predetermined optical material, which extends in a layered manner along the waveguide direction, and in which light is incident and guides the light in the waveguide direction;
It is made of the same optical material as the optical material constituting the waveguide core, and is connected to the waveguide core on the incident side of light guided to the waveguide core and extends in a layered direction in a direction inclined with respect to the waveguide direction. An inclined core that receives light therein and guides the light to the waveguide core;
A clad film made of an optical material having a refractive index lower than the refractive index of the optical material constituting the inclined core, overlapping the inclined core layer;
The clad film is made of an optical material having a refractive index higher than the refractive index of the optical material constituting the clad film, which is in contact with the clad film and is thicker than the inclined core. An information storage device comprising an incident core that is incident on the inclined core.   3. The optical head according to claim 1, wherein the inclined core is inclined to either the magnetic head or the reproducing head.   3. The optical head according to claim 1, wherein the thickness of the clad film between the inclined core and the incident core is zero.

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