JP4515244B2 - Near-field optical head - Google Patents

Description

  The present invention relates to an optical head that records and reproduces information at a high density exceeding the diffraction limit of light, or a near-field optical probe that inspects the state of a sample surface with high resolution.

  In recent years, in order to cope with a rapid increase in information such as images, moving images, and music in the information-oriented society, information recording / reproducing apparatuses have been increased in capacity and size. In an information recording / reproducing apparatus using light, since the recording density depends on the light wavelength, the density has been increased by using light having a short wavelength. As a method for realizing the recording density independent of the wavelength, a recording / reproducing principle using near-field light has attracted attention. In addition, an apparatus for inspecting a recording medium or its master is required to have high performance, and an apparatus for inspecting a medium on which information is recorded at a high density at high speed is required. The probe of the medium inspection apparatus reproduces the actual information reproduction by evaluating the medium surface by the same principle as the head of the recording / reproducing apparatus, or more precise by evaluating the medium surface by the principle of the scanning probe microscope. There are things to be inspected or a combination of both.

  The recording / reproducing apparatus using the near-field optical head has the same basic configuration as the conventional magnetic disk apparatus, and uses a near-field optical head instead of the magnetic head. In such a near-field optical head, light emitted from an optical fiber or an optical waveguide is changed in direction by reflection on a reflection surface and condensed through a lens to irradiate light to an optical minute aperture (Patent Document) 1). This will be described in more detail with reference to FIGS.

  FIG. 10 is a sectional view of a typical structure of a near-field optical head 1000 according to the prior art. The near-field optical head 1000 has a structure in which a light reflecting substrate 1001 and a near-field optical element substrate 1002 are bonded, and an optical fiber 103 is sandwiched and fixed between the two substrates. The light reflecting substrate 1001 is made of Si and has a V groove 1003 and a mirror surface 1004. Both the V-groove 1003 and the mirror surface 1004 are formed by Si anisotropic crystal etching and have a surface having an angle of about 55 ° from the substrate surface. The optical fiber 103 is fixed to the V groove 1003 and bonded.

  The near-field optical element substrate 1002 is made of glass, has a microlens 1005 on the upper surface, an air floating surface 1006 and a conical tip 1007 on the lower surface. The conical tip 1007 is covered with a light-shielding film (not shown), but the light-shielding film is removed only in a minute region of the tip end 1008. Light from a laser (not shown) is introduced into the near-field optical head 1000 by the optical fiber 103, emitted from the end face of the optical fiber 103 as emitted light 1011, reflected by the mirror surface 1004, and then collected by the microlens 1005. The cone tip 1007 is irradiated inside. A part of the light energy is distributed as near-field light 1012 in the vicinity of the tip tip 1008 where the light shielding film is removed. The near-field light 1012 interacts with a data mark on the surface of a recording medium (not shown), and the scattered light generated as a result is detected, thereby enabling high-density information recording / reproduction.

  FIG. 11 is a view showing the bottom surface side of the light reflecting substrate 1001 described above, that is, the side bonded to the near-field optical element substrate 1002. A V-groove 1003 is formed in the light reflecting substrate 1001, and the optical fiber 103 is bonded and fixed thereto. The end of the V groove 1003 is a mirror surface 1004. Adhesion between the optical fiber 103 and the V-groove 1003 is by an adhesive. Typically, an adhesive is applied to the optical fiber 103 and is bonded by being inserted into the V-groove 1003.

Since the near-field optical head manufactured in this way is small and has high light efficiency, high-density recording and reproduction can be performed by scanning close to the surface of the recording medium. In addition, the probe of the medium inspection apparatus is also capable of high-speed scanning because it floats close to the rotating medium and can inspect a wide area of the medium surface in a short time.
International Patent Publication No. 00/28536 pamphlet (pages 41-46, 1-6, 8, 21, 24-30, 41-45)

  However, in the near-field optical head according to the related art described above, when the optical fiber 103 is bonded and fixed to the light reflecting substrate 1001, an adhesive is applied to the optical fiber 103 and then fixed to the V groove 1003 of the light reflecting substrate 1001. Therefore, the adhesive flows out to the mirror surface 1004 and stains the surface of the mirror surface 1004. The mirror surface 1004 must reflect the light from the optical fiber 103 with high efficiency, but the reflection is disturbed due to contamination by the adhesive, and the near-field optical element substrate 1002 cannot be irradiated with light with high efficiency. There was a problem.

In order to prevent this problem, there may be a method of tilting the light reflecting substrate 1001 so that the adhesive does not reach the mirror surface 1004 when the optical fiber 103 is bonded to the light reflecting substrate 1001. However, in order to ensure stable adhesion by uniformly applying the adhesive to the entire side surface of the optical fiber 103, it is desirable that the light reflecting substrate 1001 be adhered while being held horizontally. Further, as another method for preventing this problem, there is a method of preventing the adhesive from reaching the mirror surface 1004 by using less adhesive.
However, it is necessary for the adhesive to securely bond the optical fiber 103 and the V-groove 1003, and a sufficient amount for fixing the adhesive surface of the cylindrical optical fiber 103 and the V-groove 1003 whose side surface is flat. It is desirable to use an adhesive. It is necessary to fix the optical fiber 103 and the light reflecting substrate 1001 with an accuracy of less than a micron, and even if a slight deviation occurs, the optical efficiency of the head is greatly deteriorated. For a near-field optical head with high light efficiency and good S / N ratio, the optical fiber 103 and the light reflecting substrate 1001 must be firmly fixed, and the adhesive should not adhere to the mirror surface 1004. . The near-field optical head according to the prior art cannot satisfy both conditions at the same time.

According to a first aspect of the present invention for solving the above-described problems, a substrate having a first groove, an optical fiber that is bonded to the first groove with an adhesive and introduces light propagated from a light source, and faces a recording medium And a near-field light generating element that converts the propagation light whose path has been changed through a reflection surface into near-field light, and interacts with the recording medium surface via the near-field light. In the near-field optical head for recording information on the recording medium or reproducing information recorded on the recording medium, the substrate intersects with the first groove and becomes a relief groove for the adhesive. The near-field optical head is characterized by further having a groove.
The second aspect of the present invention is the first aspect, wherein the depth of the second groove is the same as the depth of the first groove, or the depth of the first groove. The near-field optical head is characterized by deepness.

    According to a third aspect of the present invention, in the first or second aspect, the substrate includes a first substrate on which the reflective surface is formed, and a second substrate that includes the near-field light generating element. The near-field optical head has the first groove and the second groove on the first substrate surface.

    According to a fourth aspect of the present invention, there is provided the near-field optical head according to the third aspect, wherein one end of the first groove opposite to the light source has the reflecting surface. .

    According to a fifth aspect of the present invention, in the third or fourth aspect, the first substrate is made of Si, and the first groove and the second groove are crystalline anisotropic of the Si. The near-field optical head is a V-shaped groove formed by reactive etching.

    In addition, according to a sixth aspect of the present invention, in any one of the third to fifth aspects, the second substrate has a convex protrusion that fits into the second groove. It is in the near-field optical head.

    According to a seventh aspect of the present invention, in any one of the third to sixth aspects, a lens that condenses the propagating light reflected by the reflecting surface on the near-field light generating element is the second lens. The near-field optical head is provided in a substrate.

    According to an eighth aspect of the present invention, in the first or second aspect, the optical fiber generates the near-field light by changing a path of the propagation light at one end opposite to the light source. A near-field optical head having the reflective surface leading to an element.

    According to a ninth aspect of the present invention, in the eighth aspect, the substrate is made of Si, and the first groove and the second groove are formed by crystal anisotropic etching of the Si. The near-field optical head is characterized by being a V-shaped groove.

    According to a tenth aspect of the present invention, in the eighth or ninth aspect, the substrate has a lens for condensing the propagating light reflected by the reflecting surface on the near-field light generating element. It is in the characteristic near-field optical head.

    The eleventh aspect of the present invention is characterized in that, in any one of the first to tenth aspects, the near-field light generating element has an optical aperture smaller than the wavelength of the propagating light. Located in the near-field optical head.

    The twelfth aspect of the present invention is the reflection surface according to any one of the first to eleventh aspects, wherein the depth of the first groove is a boundary between the intersection with the second groove. The near-field optical head is characterized in that the side differs from the light source side.

    The thirteenth aspect of the present invention is the near-field optical head according to any one of the first to twelfth aspects, wherein the second groove reaches the side surface of the substrate. .

  According to the present invention, a sufficient amount of adhesive for bonding the optical fiber and the near-field optical head is used for adhesion, and the near-field optical head is held horizontally so that the adhesive is uniformly applied to the entire side surface of the optical fiber. The mirror surface can be bonded in a spread state, and since the excess adhesive flows out into the adhesive escape groove and does not reach the mirror surface, the mirror surface is guaranteed to have a high reflectance. Thereby, a near-field optical head having high mechanical strength and high light efficiency can be realized.

Further, according to the present invention, both the fixing groove for fixing the optical fiber and the adhesive escape groove can be manufactured with high shape accuracy. In addition, the structure is suitable for mass production at low cost, and a low-cost near-field optical head can be realized with stable high performance.
Further, according to the present invention, since the resolution is determined not by the wavelength of propagating light but by the size of the optical aperture, a near-field optical head having a resolution exceeding the diffraction limit of light can be realized.
Further, according to the present invention, the light from the optical fiber can be reflected toward the near-field optical element substrate, and a near-field optical head having a high recording density with a small size and a low flying height can be realized.

  In addition, according to the present invention, the optical fiber stops at the intersection of the fixing groove and the adhesive escape groove, and alignment in the front-rear direction of the optical fiber is not required, so that high assembly accuracy can be realized at low cost.

  Further, according to the present invention, it is possible to realize stable adhesion to the near-field optical element substrate without causing excess adhesive to flow out to the side surface of the light reflecting substrate and contaminating the upper surface of the light reflecting substrate.

  Further, according to the present invention, the near-field optical element substrate and the light reflecting substrate can be easily assembled with high positional accuracy, and a high-performance and low-cost near-field optical head can be realized.

  In addition, according to the present invention, the near-field optical head can be manufactured from a single substrate, and the head becomes small, so that it has a high S / N ratio by reducing the flying height from the surface of the recording medium. A high recording density head can be realized.

The best mode for carrying out the present invention will be described below with reference to the drawings.
(Embodiment 1)
FIG. 1 shows an outline of an information reproducing apparatus using a near-field optical head according to Embodiment 1 of the present invention. The information reproducing apparatus according to the present embodiment has a basic configuration similar to that of a conventional magnetic disk apparatus, and a near-field optical head 106 having an optical minute aperture (not shown) for generating near-field light is connected to a recording medium 107. In order to rotate the recording medium 107 at a high speed in a state close to several tens of nanometers on the surface and the near-field optical head 106 always floats in a fixed relative arrangement with the recording medium 107, the flexure 105 is placed at the tip of the suspension arm 104. Is formed. The suspension arm 104 is movable in the radial direction of the recording medium 107 by a voice coil motor (not shown). Here, the near-field optical head 106 is disposed so that the optical minute aperture faces the recording medium 107.

  The light propagation part that guides the light beam from the laser 101 to the vicinity of the flexure 105 includes an optical fiber 103 fixed to the lens 102 and the suspension arm 104.

  Although the optical fiber 103 is used here, an optical waveguide or aerial light propagation may be used. Further, if necessary, the laser 101 can be subjected to intensity modulation by the circuit system 108. In order to make the outline easy to understand, the suspension arm 104, the flexure 105, and the near-field optical head 106 are shown in an exploded form, but in actuality, they are connected and fixed as necessary.

  The cross section of the near-field optical head 106 is the same as that of the near-field optical head according to the prior art described with reference to FIG. 10, and two substrates or components are bonded so as to sandwich the optical fiber. Of these two parts, the part farther from the recording medium 107 is called a light reflecting portion.

  FIG. 2 shows a perspective view of the light reflecting portion 200 in the near-field optical head 106 according to Embodiment 1 of the present invention. The light reflecting unit 200 includes a light reflecting substrate 201 and an optical fiber 103. The light reflecting substrate 201 is formed with a fixing groove 202 and an adhesive escape groove 204 intersecting with the fixing groove 202. The end of the fixing groove 202 is a mirror surface 203. The optical fiber 103 is bonded and fixed to the fixing groove 202. The light reflecting substrate 201 is made of Si, and both the fixing groove 202 and the adhesive escape groove 204 are formed by crystal anisotropic etching of Si.

  3A and 3B are a top view and a cross-sectional view of the light reflecting substrate 201, respectively. The adhesive escape groove 204 is formed deeper than the fixed groove 202. The adhesive application unit 205 is a surface on which the adhesive applied to the side surface of the optical fiber 103 adheres the optical fiber 103 and the side surface of the fixing groove 202. Of the adhesive applied to the optical fiber 103, it is diffused by flowing through the fixed groove 202 except that it is consumed for bonding the optical fiber 103 and the fixed groove 202, and a part of the adhesive groove 202 intersects with the adhesive escape groove 204. Reach the department. Since the adhesive escape groove 204 is dug deeper than the fixed groove 202, the adhesive flows into the adhesive escape groove 204 from the intersection and advances in the direction of the mirror surface 203 at the end of the fixed groove 202. Absent.

Thereby, even when the optical fiber 103 to which an unnecessary amount of adhesive is applied is bonded, the excess adhesive escapes into the adhesive escape groove 204, so that there is no possibility that the mirror surface 203 is soiled. The optical fiber 103 and the fixing groove 202 are bonded with sufficient strength, and the mirror surface 203 can always maintain a high light reflectance. It is not necessary to strictly control the amount of adhesive in order to ensure sufficient strength of adhesion, and it may be applied slightly more than the required amount. Since both the fixing groove 202 and the adhesive escape groove 204 are formed by crystal anisotropic etching of Si, the fixing groove 202 and the adhesive escape groove 204 have high shape accuracy and can be manufactured at low cost. A near-field optical head having sufficient mechanical strength and high light efficiency can be stably manufactured at low cost.
(Embodiment 2)
4A and 4B are a top view and a cross-sectional view, respectively, of the light reflecting substrate of the near-field optical head according to Embodiment 2 of the present invention. The light reflecting substrate is formed with a fixing groove 301 and an adhesive escape groove 304 intersecting with the fixing groove 301. A portion 302 of the fixing groove 301 ahead of the intersection with the adhesive escape groove 304 is a shallower groove than the front portion of the intersection, and the end portion is a mirror surface 303. FIG. 5 shows a perspective view of the light reflecting substrate. Although the optical fiber 103 is fixed to the fixing groove 301, the portion 302 ahead of the intersection of both grooves is a shallower groove than the fixing groove 301. It is fixed so as to abut against the side surface 305.

The near-field optical head having such a structure does not adhere to the mirror surface 303 when excess adhesive flows into the adhesive escape groove 304. Since the light from the optical fiber 103 is reflected by a mirror surface with extremely high flatness, there is little light loss and the near-field optical element substrate is irradiated with high light efficiency. Thereby, a near-field optical head with high light efficiency is realized. Further, when the optical fiber 103 is bonded and fixed to the fixing groove 301, the tip abuts against the side surface 305 of the adhesive escape groove 304, so that the fixing position accuracy in the optical axis direction is determined by the both groove forming accuracy. Thereby, the process of bonding and fixing the optical fiber 103 and the light reflecting substrate 300 can be easily performed with high accuracy. (Embodiment 3)
FIG. 6 is a perspective view of the light reflecting substrate 400 of the near-field optical head according to Embodiment 3 of the present invention. The light reflection substrate 400 is formed with a fixing groove 401, an adhesive escape groove 402 intersecting with the fixing groove 401, and an adhesive escape groove extension 403 intersecting with the adhesive groove. The optical fiber 103 is bonded and fixed to the fixing groove 401. The portion of the fixing groove 401 ahead of the intersection with the adhesive escape groove 402 may be the same depth as the front portion as in the first embodiment, or may be shallow as in the second embodiment. . The feature of this embodiment is that it has an adhesive escape V-groove extension 403 in addition to the structure of the first or second embodiment. With such a structure, the volume for receiving excess adhesive becomes larger, the allowable amount of adhesive in the assembly process becomes larger, and control becomes easier.
(Embodiment 4)
FIG. 7 is a perspective view of the light reflecting substrate 500 of the near-field optical head according to Embodiment 4 of the present invention. The light reflecting substrate 500 is formed with a fixing groove 501, an adhesive escape groove 502 intersecting with the fixing groove 501, and an adhesive escape groove extension 503 intersecting therewith. The optical fiber 103 is bonded and fixed to the fixing groove 501. The difference between the present embodiment and the third embodiment is that the adhesive escape groove extension 503 reaches the side surface 504 of the light reflecting substrate 500. With such a structure, excess adhesive can flow out from the adhesive escape V-groove extension to the side surface of the light reflecting substrate. Thus, even if a large amount of adhesive is applied to the optical fiber 103, it does not overflow on the upper surface of the light reflecting substrate 500, and does not hinder the adhesion to the near-field optical element substrate (not shown).
(Embodiment 5)
FIG. 8 is a perspective view of the light reflection substrate 400 and the near-field optical element substrate 700 of the near-field optical head according to Embodiment 5 of the present invention. Since the light reflecting substrate 400 is the same as that implemented in the third embodiment, the description thereof is omitted. A feature of this embodiment is that the near-field optical element substrate 700 has a protrusion 701. The protrusion 701 is fitted into the adhesive escape V-groove extension of the light reflecting substrate 400 and is fixedly bonded. With such a structure, alignment at the time of assembly becomes easier, and the manufacturing cost is reduced. Further, since the adhesion area between the light reflection substrate 400 and the near-field optical element substrate 700 is increased, the adhesion force is increased and a near-field optical head having a high mechanical strength is obtained.
(Embodiment 6)
FIG. 9 shows a near-field optical head 600 according to Embodiment 6 of the present invention. The near-field optical element substrate 60 has a fixing groove 603, an adhesive escape groove 604, and a microlens 607. The microlens 607 is formed in a region recessed from the surface of the near-field optical element substrate 601. The tip surface 605 of the optical fiber 602 is polished obliquely at an angle of 45 degrees with respect to the optical axis. The feature of this embodiment is that there is no light reflecting substrate, and the near-field optical head 600 is composed of only the near-field optical element substrate 601 and the optical fiber 602. Such a structure is possible because the front end surface 605 of the optical fiber 602 is polished obliquely.
The optical fiber 602 is fixed to the fixing groove 603 using an adhesive. However, if too much adhesive is applied, excess adhesive flows into the adhesive escape groove 604. Thereby, it can prevent that an adhesive agent adheres to the optical fiber front end surface 605 and the micro lens 607. The optical fiber front end surface 605 and the microlens 607 always have high light transmission efficiency, and the optical fiber 602 coated with a sufficient adhesive is firmly fixed to the fixing groove 603.

  Such a small near-field optical head can fly finely with respect to the surface of the recording medium, and the interaction via the near-field light becomes more localized and strong. A recording / reproducing head having a / N ratio is realized. In the present embodiment, the near-field optical element substrate 600 is made of glass. However, the near-field optical element substrate 600 can also be made of a Si substrate. In this case, the fixing groove 603 and the adhesive are used as in the first embodiment. The escape groove 604 can be a V groove formed by crystal anisotropic etching of Si. Light from an unillustrated light source uses a wavelength in the infrared region that transmits Si, thereby realizing a small and thin near-field optical head composed of a single substrate.

1 shows an outline of an information reproducing apparatus using a near-field optical head according to Embodiment 1 of the present invention. The perspective view of the light reflection part 200 among the near-field optical heads 106 which concern on Embodiment 1 of this invention is shown. A top view (a) and a cross-sectional view (b) of the light reflecting substrate 201 are shown. The top view (a) and sectional drawing (b) of the light reflection board | substrate of the near-field optical head which concerns on Embodiment 2 of this invention are shown. The perspective view of a light reflection board is shown. The perspective view of the light reflection board | substrate 400 of the near-field optical head which concerns on Embodiment 3 of this invention is shown. The perspective view of the light reflection board | substrate 500 of the near-field optical head which concerns on Embodiment 4 of this invention is shown. The perspective view of the light reflection board | substrate 400 of the near-field optical head which concerns on Embodiment 5 of this invention, and the near-field optical element board | substrate 700 is shown. 9 shows a near-field optical head 600 according to Embodiment 6 of the present invention. A sectional view of a typical structure of a near-field optical head 1000 according to the prior art is shown. The bottom surface side of the light reflection board | substrate 1001 by a prior art is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Laser 102 Lens 103 Optical fiber 104 Suspension arm 105 Flexure 106 Near-field optical head 107 Recording medium 108 Circuit system
DESCRIPTION OF SYMBOLS 200 Light reflection part 201 Light reflection board 202 Fixing groove 203 Mirror surface 204 Adhesive escape groove 205 Adhesive application part 301 Fixing groove 302 A part ahead of the intersection of the fixation groove 301 with the adhesive escape groove 304 303 Mirror surface 304 Adhesive escape groove 305 Side surface of adhesive escape groove 304 306 End face of optical fiber 103 400 Light reflecting substrate 401 Fixed groove 402 Adhesive escape groove 403 Adhesive escape groove extension 500 Light reflecting substrate 501 Fixed groove 502 Adhesive escape groove 503 Adhesive escape groove extension 504 Side surface of light reflecting substrate 500 600 Near-field optical head 601 Near-field optical element substrate 602 Optical fiber 603 Fixed groove 604 Adhesive escape groove 605 Optical fiber tip surface 607 Micro lens 700 Near-field optical element substrate 701 Protrusion 1000 Near-field light by conventional technology Head 1001 Light reflection substrate 1002 Near-field optical element substrate 1003 V groove 1004 Mirror surface 1005 Micro lens 1006 Air floating surface 1007 Conical tip 1008 Tip tip 1011 Emission light 1012 Near-field light

Claims (8)

A first substrate having a first groove comprising an adhesive portion for applying an adhesive and a reflective surface;
An optical fiber that is bonded to the bonding portion and introduces light propagated from a light source;
A second substrate provided with a near-field light generating element that is provided facing a recording medium and converts the propagating light whose optical path has been changed through the reflecting surface into near-field light,
In a near-field optical head that records information on the recording medium or reproduces information recorded on the recording medium by interacting with the surface of the recording medium via the near-field light,
The first substrate intersects with the first groove, is provided between the adhesive portion and the reflective surface and spaced from the reflective surface, and serves as a relief groove for the adhesive. A groove, and a third groove that intersects the second groove and is provided in a direction parallel to the first groove,
The near-field optical head, wherein the second substrate has a convex protrusion that fits into the third groove.   2. The near-field optical head according to claim 1, wherein the depth of the second groove is the same as the depth of the first groove or deeper than the depth of the first groove.   The near-field optical head according to claim 1, wherein one end of the first groove opposite to the light source has the reflective surface.   4. The first substrate is made of Si, and the first groove and the second groove are V-shaped grooves formed by crystal anisotropic etching of Si. The near-field optical head described in 1.   5. The near-field optical head according to claim 3, further comprising a lens in the second substrate for condensing the propagation light reflected by the reflecting surface on the near-field light generating element. . The near-field light-generating element, the near-field optical head according to any one of claims 1 to 5, wherein a small optical aperture than the wavelength of the propagation light. The depth of the said 1st groove | channel is the shallower than the said light source side, The said reflective surface side is shallower than the said 2nd groove | channel, The any one of Claims 1-6 characterized by the above-mentioned. The near-field optical head described in 1. It said third groove, near-field optical head according to any one of claims 1 to 7, and the first groove extends direction of the substrate, characterized in that it reaches a plane perpendicular.

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