NEAR-FIELD OPTICAL HEAD

Abstract: There is provided a near-field optical head promoting reliability of a head by improving mechanical strength thereof. An edge portion 23 of a head front end portion 22 is constituted by a side 26 where a bottom face 24 and a side face 25 of the head intersect with each other. The bottom face 24 and the side face 25 intersect with each other substantially orthogonally. When the edge portion 23 is viewed microscopically (nm level), the edge portion 23 is provided with a curved face. A radius of curvature Rt thereof corresponds with a reproducible bit size and the smaller (the sharper) of the radius of curvature Rt, the higher density recording can be carried out. The edge portion 23 can be fabricated at an angle determined by crystal faces when the edge portion 23 is formed by using anisotropic etching of Si.

Description: TECHNICAL FIELD The present invention relates to a near-field optical recording arrangement, further particularly to a near-field optical recording arrangement capable of promoting a resolution and enhancing a mechanical strength by devising a structure of a head, facilitating fabrication thereof and realizing high scattering efficiency of an evanescent field. BACKGROUND OF THE INVENTION At present, there has widely been spread an information reproducing device of a reproduction exclusive type represented by CD as well as CD-ROM. According to the information reproducing device, information recorded on an optical disk is reproduced by using light. For example, in the case of CD, a surface thereof is recorded with pits each having a size of substantially a wavelength of laser beam used in reproduction and a depth of substantially a quarter of the wavelength as recess and projection information and the interference phenomenon of light is utilized for reproducing the information. When a spot of laser beam is illuminated onto the pit, since the depth of the pit is a quarter of the wavelength, a difference of optical paths of reflected light reflected by a bottom face of the pit and reflected light reflected by the surface becomes a half of the wavelength of the illuminated laser beam. Therefore, the provided reflected light becomes weaker than that in the case of irradiating the spot of laser beam onto a surface at other than the pit. In this way, by detecting the intensity of the reflected light, presence or absence of the pit is determined to thereby achieve reproduction of information recorded on the optical disk. In a system of irradiating the above-described laser beam and a system of detecting thereof, a lens optical system used in a conventional optical microscope is used, however, the spot size of the laser beam cannot be made equal to or smaller than a half of the wavelength owing to a diffraction limit of light. Meanwhile, in order to increase an information recording density of the optical disk, the size of the pit must be reduced and a track pitch must be narrowed. Accordingly, when an information recording unit is constituted by a size smaller than the wavelength of the laser beam, a conventional information reproducing apparatus cannot deal therewith. In view of such a problem, in recent years, there has been proposed an optical memory utilizing technologies of a near-field optical microscope. A near-field optical microscope uses a probe having a very small aperture of, for example, a diameter equal to or smaller than the wavelength of illuminated laser beam, for example, about one tenth of the wavelength and observes a very small surface structure and an optical characteristic distribution of a sample by utilizing near-field light (a nonpropagated component in light existed in a region of optical wavelength or less from a surface of a substance: evanescent field). According to such a near-field optical microscope, by irradiating propagated light from a rear face of the sample, the near-field light is generated at the surface of the sample, the very small aperture of the probe and the surface of the sample are made to proximate to each other to a degree of the diameter of the very small aperture of the probe and the near-field light is scattered at the very small aperture by which the near-field light is taken out from the very small aperture as propagated light. The near-field light generated at the surface of the sample is accompanied by an intensity and a phase reflecting the very small structure and the optical characteristic distribution of the surface of the sample and by processing the taken-out propagated light by an optical detector, observation having a resolution which cannot be realized by a conventional optical microscope is made feasible. Further, a system of using an AFM cantilever provided with a sharpening treatment at its front end has frequently been used. There have been described technologies of forming a light transmitting tip at a front end of an AFM cantilever in a literature "Hulst et al., Appl. Phys. Lett. (1993) Vol. 62, p461", a literature "Hulst et al., SPIE (1992) Vol. 1639, p36", Japanese Patent Laid-Open No. 160719/1994 and PCT International Application Publication WO95/03561. Further, there have been described technologies of forming an AFM cantilever by a tip which does not transmit light in a literature "Zenhausern et al., Appl. Phys. Lett. (1994) vol. 65, p1623", a literature "Bachelot et al., Ultramicroscopy (1995) Vol. 61, p111" and Proceedings of Near-field Optics Research Group ("A reflective type near-field optical microscope using a metal probe and observation of a semiconductor sample having a fine structure", Proceedings of the 4th Symposium of Near-field Optics Research Group 1995, p53). By applying the above-described near-field optical technologies to an optical memory, information can be detected from an optical disk constituted by an information recording unit of a wavelength of laser beam or smaller. However, according to the above-described method of forming a very small aperture, formation of the very small aperture is difficult and a size capable of forming the aperture is provided with a limit and accordingly, there poses a problem in which a resolution is difficult to be improved to several tens nm or smaller. Meanwhile, according to the above-described method of using an AFM cantilever, the front end is subjected to the sharpening treatment and therefore, the mechanical strength is weak and there poses a problem in which the reliability is low in using the AFM cantilever as a head. For example, the tip becomes liable to be damaged by the dust on a medium face or vibration of a medium. Further, many steps of a sharpening process is needed in forming the tip and assuming the case of forming the tip at a flying head, there poses a problem in which heights of the flying head and the front end of the tip are difficult to be matched. Further, a surface area of the tip is small and accordingly, there poses a problem in which the scattering efficiency of an evanescent field is lowered. In US patent number 5,199,090, issued on 30th March 1993 and reflecting the preamble of claim 1, a near-field optical head is described, which is disposed on a slider and interfaces with a magneto-optical disk. A waveguide is provided on an end-face of the slider and a photodetector is aligned with the waveguide. A laser outputs a beam of light, which passes through the waveguide, is collimated in a lens and is then focussed by a further lens. Evanescent light leaves the head, to be reflected from a magnetic domain on the disk and picked up as returning light by the detector. US 5,497,359, issued on 5th March 1996, relates to a near-field optical disk data storage system involving a head co-operating with a storage disk. The head comprises a laser light source, a beam splitter and a lens for focussing laser light onto the recording surface of the disk. Returned light is detected in a detector, amplified and used as a data signal and also to generate a tracking-error and focus-error signal. The storage system also includes an air-bearing slider with a hemispherical lens on the back of the slider. The laser and photodetector unit and focus lens are, in one arrangement, both placed directly on the slider. A near-field optical head is also the subject of European patent application 0814468, published on 29th December 1997. This optical head comprises a series of layers performing various functions. The head has at its upper end a laser source and a pair of photodiodes. Light from the laser passes through a collimator, a grating and three grating lenses before leaving as evanescent light, which is reflected by the disk. Japanese patent application 08082633, published on 26th March 1996, concerns a near-field microscope, which employs a waveguide structure for directing light from a laser source onto a specimen table. Hence, the invention has been carried out in view of the above-described and it is an object thereof to provide a near-field optical head capable of improving a resolution and enhancing a mechanical strength, facilitating fabrication thereof and having a high scattering efficiency of an evanescent field. Disclosure of the Invention According to the invention, there is provided a near-field optical recording arrangement as recited in claim 1. Embodiments of the invention are set forth in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an outline perspective view showing a near-field optical head according to Embodiment 1 of the invention. Fig. 2 is an enlarged side view showing a front end portion of the head shown in Fig. 1. Fig. 3 is an enlarged front view showing the front end portion of the head shown in Fig. 1. Fig. 4 is an outline perspective view showing a modified example of the near-field optical head shown in Fig. 1. Fig. 5 is an outline perspective view showing a modified example of the near-field optical head shown in Fig. 1. Fig. 6 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 2 of the invention. Fig. 7 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 3 of the invention. Fig. 8 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 4 of the invention. Fig. 9 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 5 of the invention. Fig. 10 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 6 of the invention. Fig. 11 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 7 of the invention. Fig. 12 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 8 of the invention. BEST MODE FOR CARRYING OUT THE INVENTION A detailed explanation will be given of the invention by referring to the drawings as follows. Further, the invention is not limited by the embodiments. (Embodiment 1) Fig. 1 is an outline perspective view showing a near-field optical head according to Embodiment 1 of the invention. Fig. 2 is an enlarged side view showing a front end portion of the head shown in Fig. 1. The near-field optical head 100 is provided with a constitution including a head 2 in a projected shape disposed opposedly to a disk 1 and a light detecting element 3 arranged above a front end portion of the head. The head 2 is provided with a beam portion 21 and a front end portion 22 thereof is formed in an edge shape. An edge portion 23 of the front end portion 22 is constituted by a side 26 where a bottom face 24 and a side face 25 of the head 2 intersect with each other. The bottom face 24 and the side face 25 intersect substantially orthogonally to each other. When the edge portion 23 is viewed microscopically (nm level), the edge portion 23 is provided with a curved face. A radius of curvature Rt thereof and a reproducible bit size correspond with each other and the smaller (sharper) the radius of curvature Rt, the higher density recording can be carried out. The edge portion 23 can be fabricated by an angle determined by crystal faces when it is formed by using anisotropic etching of Si. Further, also in respect of a material other than Si, a considerable sharpness can be realized by accurately setting etching conditions (regardless of wet etching or dry etching). Further, the edge portion 23 is formed by intersecting two planes and the angle of intersection poses no problem. For example, the edge portion may be formed by intersecting two planes at an angle of 30 degrees or 60 degrees. When a face vertically intersecting with a side produced by the two planes is defined as a section, the edge portion 23 is provided with the same radius of curvature Rt even at any of the section. Meanwhile, when a face including the side produced by the two planes is defined as a section, the radius of curvature is nullified. In contrast thereto, according to the above-described conventional tip, an apex thereof is formed in a semispherical shape when it is microscopically viewed in any of a needle-like shape, a shape of a circular cone and a shape of a pyramid of the tip. Accordingly, when a face including the apex and a center of the spherical body is defined as a section, any of the section is provided with a radius of curvature. The radius of curvature Rt of the edge portion 23 must be equal to or smaller than the shortest bit length formed on the disk 1. When the radius of curvature Rt of the edge portion 23 is smaller than a bit length, presence or absence of a bit 11 can be read with excellent S/N. For example, when the bit length is 100 nm, the radius of curvature Rt of the edge portion 23 must substantially be smaller than about 100 nm. Next, although a width w1 of the edge portion 23 may be larger than a bit width on the disk 1, the width must not overlap a contiguous one of a track 12. Further, although a wide width portion 27 (width W2) in a projected shape may overlap a contiguous one of the track 12, in that case, a length L of the beam portion 21 may be provided to a degree of preventing cross talk from a contiguous one of the track 12. Further, as shown in Fig. 3, the edge portion 23 per se may be provided with a curvature (radius of curvature Rn). In this case, the bottom face 24 is constituted by a curved face and by intersecting the bottom face 24 with the side face 25, the edge portion 23 is formed. Also in such an edge portion 23, a radius of curvature Rt similar to that in Fig. 2 is provided when it is viewed microscopically. The near-field optical head 100 cannot track completely on the bit 11 and accordingly, a deviation in a direction orthogonal to the track is corrected by a feedback control. In this case, when the radius of curvature Rn in the direction orthogonal to the track is to a degree of the bit width, a signal (presence or absence of bit) by the feedback control in the direction orthogonal to the track becomes excessively large to thereby constitute noise and the presence or absence of the bit in the direction of the track cannot be read as a signal. Accordingly, it is preferable to make the noise smaller than the signal of the presence or absence of the bit in the direction of the track by about two orders even when the noise is reduced by a filter from a feedback frequency. Further, in view of the current practical technical level (DVD or the like), the noise level needs to be smaller than the signal level by four orders or more. From the above-described, although the radius of curvature Rn in the direction orthogonal to the track is pertinent to be infinitive, it seems to pose practically no problem when the radius of curvature is about five times as large as the bit width, preferably, fifty times or more as much as the bit width. Referring back to Fig. 2, a distance d between the edge portion 23 and the disk 1 is controlled to be equal to or smaller than the wavelength of light. In controlling the distance d, a so-to-speak flying head of a hard disk drive (HDD) is used and the near-field optical head 100 is flown by air film lubrication. When the fly head technology is used, a flow path in a shape of a wedge film needs to be formed by installing a tapered face at the near-field optical head 100. According to the fly head technology, the distance d can be controlled at around 50 nm. Further, as in the case of an AFM cantilever, the distance may be detected and a feedback control may be carried out by a piezoelectric element or the like. Further, the control may be realized by bringing about a contact state interposing a thin lubrication film (oil or water or the like) of about several nm therebetween or a complete contact state may be brought about. When light 4 is illuminated by an incident angle satisfying a total reflection condition from a light source (illustration is omitted) to a rear face of the disk 1, an evanescent field 41 is generated at the surface of the disk. By inserting the edge portion 23 thereinto, scattered light 42 is generated. The optical intensity of the scattered light 42 is changed by presence or absence of the bit 11. The generated scattered light 42 is received by the light detecting element 3. The light detecting element 3 carries out photoelectric conversion in accordance with the optical intensity of the scattered light 42. Thereby, information on the disk 1 can be reproduced. Further, the front end portion 22 of the head may be formed in a shape of a sword as shown in Fig. 4 other than a shape of a short strip as shown in Fig. 1. Further, it may be formed in a circular shape as shown in Fig. 5. Further, in respect of a state of recording onto the disk 1, the bit may be recorded by using a difference in transmittance or reflectance or may be recorded as recess and projection. Further, the near-field light includes far field light. As mentioned above, according to the near-field optical head 100, in comparison with the conventional tip subjected to a sharpening treatment, the edge portion 23 is excellent in the mechanical strength and accordingly, the reliability of the head is promoted. Next, in forming the tip, many steps of a sharpening process are needed, further, matching of heights of the front end of the tip and a slider is difficult in view of fabrication. In contrast thereto, the edge portion 23 can be formed comparatively easily at a portion of a head slider by an etching treatment and the matching of heights of the edge portion 23 and a bottom face of the slider is dispensed with. Further, an area of scattering the evanescent field 41 of the edge portion 23 is larger than that of the tip and accordingly, the provided intensity of scattered light is made stronger. (Embodiment 2) Fig. 6 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 2 of the invention. The near-field optical head 200 is constructed by a constitution which is more specific than that of the near-field optical head 100 according to Embodiment 1, mentioned above. According to the near-field optical head 200, an edge portion 202 similar to the above-described (refer to Fig. 2) is formed at a bottom face of a head slider 201. A tapered face 203 is provided on a side thereof opposed to the edge portion 202. A flow path in a shape of a wedge film is produced by the tapered face 203 and a disk 204. Further, formation of the edge portion 202 is carried out by an etching treatment. The near-field optical head 200 is supported by a suspension arm (illustration is omitted) and is driven by a voice coil motor (illustration is omitted). Further, a lens 205 for condensing scattered light and a light detecting element 206 are arranged in a skewed upper direction of the head slider 201. When light 207 is illuminated from a light source (illustration is omitted) to a rear face of the disk 204 by an incident angle satisfying the total reflection condition, an evanescent field 208 is generated at the surface of the disk. The head slider 201 is flown obliquely and accordingly, the edge portion 202 approaches the face of the disk and scatters light. The optical intensity of scattered light 209 is changed by-presence or absence of a bit 210. The generated scattered light 209 is condensed by the lens 205. The light detecting element 206 is arranged at a condensing destination and the scattered light 209 is received by the light detecting element 206. The light detecting element 206 carries out photoelectric conversion in accordance with the optical intensity of the scattered light 209. Thereby, information on the disk 204 is reproduced. According to the near-field optical head 200, by carrying out the flying-head technology, the distance between the edge portion 202 and the disk 204 can easily be controlled. Further, only the edge portion 202 is formed at the head slider 201 and accordingly, the near-field optical head 200 is more compact than a general magnetic head and the cost becomes lower. (Embodiment 3) Fig. 7 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 3 of the invention. The near-field optical head 300 is constructed by a constitution which is more specific than that of the near-field optical head 100 according to Embodiment 1, mentioned above. According to the near-field optical head 300, an edge portion 302 similar to the above-described (refer to Fig. 2) is formed at a bottom face of a head slider 301. Further, a stepped portion 303 is formed at a vicinity of the edge portion 302 in the head slider 301. A light detecting element 304 is provided at the stepped portion 303. A tapered face 305 is provided on the side thereof opposed to the edge portion 302. A flow path in a shape of a wedge film is produced by the tapered face 305 and a disk 306. Further, formation of the edge portion 302 is carried out by an etching treatment. The near-field optical head 300 is supported by a suspension arm (illustration is omitted) and is driven by a voice coil motor (illustration is omitted). When light 307 is illuminated from a light source (illustration is omitted) to a rear face of the disk 306 at an incident angle satisfying the total reflection condition, an evanescent field 308 is generated at a surface of the disk. The head slider 301 is flown obliquely and therefore, the edge portion 302 approaches the face of the disk and scatters light. The optical intensity of scattered light 309 is changed by presence or absence of a bit 310. The generated scattered light 309 is received by the light detecting element 304 provided at a vicinity of the edge portion 302 in the head slider 301. The light detecting element 304 carries out photoelectric conversion in accordance with the optical intensity of the scattered light 309. Thereby, information on the disk 306 is reproduced. According to the near-field optical head 300, the light detecting element 304 is provided directly in the head slider 301 and accordingly, the head becomes compact. Further, by providing the light detecting element 304 at the vicinity of the edge portion 302, the light detecting efficiency is improved. (Embodiment 4) Fig. 8 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 4 of the invention. The near-field optical head 400 is constructed by a constitution which is more specific than that of the near-field optical head 100 according to Embodiment 1, mentioned above. An edge portion 402 similar to the above-described (refer to Fig. 2) is formed at a bottom face of a head slider 401. Further, a stepped portion 403 is formed at a vicinity of the edge portion 402 in the head slider 401. A light detecting element 404 is provided at the stepped portion 403. Further, a metal film 405 is formed at a bottom face of the head slider 401. The edge portion 402 is formed by the metal film 405. Because the scattering efficiency of a metal edge is higher than that of an edge of a dielectric member. Further, the metal film may be formed not over the entire bottom face of the head slider 401 but only at the edge portion 402. A tapered face 406 is provided on a side thereof opposed to the edge portion 402. A flow path in a shape of a wedge film is produced by the tapered face 406 and a disk 407. Further, formation of the edge portion 402 is carried out by an etching treatment. The near-field optical head 400 is supported by a suspension arm (illustration is omitted) and is driven by a voice coil motor (illustration is omitted). At a portion where the head slider 401 is not present, light 408 is incident on the disk 407 by the total reflection condition and therefore, all thereof is reflected. At a portion where the head slider 401 is present (other than edge portion) with a distance equal to or smaller than the wavelength from the disk 407, a distance between the head slider 401 and the disk 407 is substantially equal to null and accordingly, the light 408 penetrates the surface of the disk. Transmitted light (illustration is omitted) is reflected by the metal film 405 at the bottom face of the head slider 401. Or, when the metal film 405 is formed partially, light is reflected by a portion with the metal film 405. In this way, by reflecting light by forming the metal film 405 at the bottom face of the head slider 401, stray light entering the light detecting element 404 is reduced. Further, not the reflecting film but an absorbing film may be formed. However, it is not preferable to form the edge portion 402 by an absorbing film. The principle of reproducing information is the same as that in Embodiment 3. That is, the edge portion 402 of the flown head slider 401 is made to enter an evanescent field 409 at the surface of the disk to thereby scatter light. The optical intensity of the scattered light 410 is changed by presence or absence of a bit 411. The generated scattered light 410 is received by the light detecting element 404 provided at a vicinity of the edge portion 402 in the head slider 401. The light detecting element 404 carries out photoelectric conversion in accordance with the optical intensity of the scattered light 410. Thereby, information on the disk 407 is reproduced. (Embodiment 5) Fig. 9 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 5 of the invention. The near-field optical head 500 is constructed by a constitution substantially the same as the near-field optical head 400 according to Embodiment 4, mentioned above, and differs therefrom in that a waveguide path is formed at the light detecting element. According to the near-field optical head 500, an edge portion 502 similar to the above-described (refer to Fig. 2) is formed at a bottom face of a head slider 501. A stepped portion 503 is formed at a vicinity of the edge portion 502 in the head slider 501. A light detecting element 504 and a waveguide path 505 are provided at the stepped portion 503. A metal film 506 is formed at a bottom face of the head slider 501. The edge portion 502 is formed by the metal film 506. Because the scattering efficiency of a metal edge is higher than that of an edge of a dielectric member. Further, the metal film 506 may be formed not over the entire bottom face of the head slider 501 but only at the edge portion 502. A tapered face 507 is provided on a side thereof opposed to the edge portion 502. A flow path in a shape of a wedge film is produced by the tapered face 507 and a disk 508. Further, formation of the edge portion 502 is carried out by an etching treatment. The near-field optical head 500 is supported by a suspension arm (illustration is omitted) and is driven by a voice coil motor (illustration is omitted). When light 509 is illuminated from a light source (illustration is omitted) to a rear face of the disk 508 at an incident angle satisfying the total reflection condition, an evanescent field 510 is generated at a surface of the disk. The head slider 501 is obliquely flown and accordingly, the edge portion 502 approaches the face of the disk and scatters light. The optical intensity of scattered light 511 is changed by presence or absence of a bit 512. The generated scattered light 511 is received by the light detecting element 504 after having passed through the waveguide path 505 provided at a vicinity of the edge portion 502 in the head slider 501. The light detecting element 504 carries out photoelectric conversion in accordance with the optical intensity of the scattered light 511. Thereby, information on the disk 508 is reproduced. According to the near-field optical head 500, the waveguide path 505 is formed on the light detecting element 504 and accordingly, the scattered light 511 from the edge portion 502 can selectively be guided to the light detecting element 504. Thereby, other scattered light does not enter the light detecting element 504 and therefore, an S/N ratio is promoted. Further, a lens may be provided at a front end of the waveguide path 505. Further, the light detecting element 504 is directly provided at the head slider 501 and accordingly, the head becomes compact. Further, by providing the light detecting element 504 at the vicinity of the edge portion 502, the light detecting efficiency is improved. Further, light which has transmitted through the surface of the disk is reflected by the metal film 506 formed at the bottom face of the head slider 501. Therefore, stray light entering the waveguide path 505 is reduced. In addition, scattered light produced by small defect, recess and protrusion or the like other than the bit on the disk 508 or light which has transmitted through the head slider 501 or the like constitutes stray light, however, the waveguide path 505 is provided and accordingly, influence of these stray light is difficult to be effected. (Embodiment 6) Fig. 10 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 6 of the invention. The near-field optical head 600 is constituted not by a system of totally reflecting light at a surface of a disk but by a system of irradiating light from above a head slider. According to the near-field head slider 600, a head slider 601 is constituted by a material having transparency and an edge portion 602 similar to the above-described (refer to Fig. 2) is formed at a bottom face of the head slider 601. Further, a stepped portion 603 is formed at a vicinity of the edge portion 602 in the head slider 601. The stepped portion 603 is provided with a light detecting element 604 and a waveguide path 605. A light source 606 and a lens 607 are arranged on an oblique upper side of the head slider 601. A tapered face 608 is provided on a side thereof opposed to the edge portion 602. A flow path in a shape of a wedge film is produced by the tapered face 608 and a disk 609. Further, formation of the edge portion 602 is carried out by an etching treatment. The near-field optical head 600 is supported by a suspension arm (illustration is omitted) and is driven by a voice coil motor (illustration is omitted). Light 610 from the light source 606 is condensed by the lens 607 and illuminates the edge portion 602 after having passed through the head slider 601. Thereby, an evanescent field 611 is generated at a surface of the edge portion 602. The head slider 601 is flown obliquely and accordingly, the edge portion 602 approaches a face of the disk and scatters light. The optical intensity of the scattered light 612 is changed by presence or absence of a bit 613. Generated scattered light 612 is received by the light detecting element 604 after having passed through the waveguide path 605 provided at a vicinity of the edge portion 602 in the head slider 601. The light detecting element 604 carries out photoelectric conversion in accordance with the optical intensity of the scattered light 612. Thereby, information on the disk 609 is reproduced. According to the near-field optical head 600, the light source 606 is arranged on the same side with the head and therefore, the apparatus can be made compact. (Embodiment 7) Fig. 11 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 7 of the invention. According to the near-field optical head 700, a head slider 701 is constituted by a material having transparency and an edge portion 702 similar to the above-described (refer to Fig. 2) is formed at a bottom face of the head slider 701. Further, a light detecting element 703 and a waveguide path 704 are provided at a vicinity of the edge portion 702 in the head slider 701. A light source 705 and a lens 706 are integrated to the head slider 701. A tapered face 707 is provided at a side thereof opposed to the edge portion 702. A flow path in a shape of a wedge film is produced by the tapered face 707 and a disk 708. Further, formation of the edge portion 702 is carried out by an etching treatment. The near-field optical head 700 is supported by a suspension arm (illustration is omitted) and is driven by a voice coil motor (illustration is omitted). Light 709 from the light source 705 is condensed by the lens 706 and illuminates the edge portion 702 after having transmitted through the head slider 701. Thereby, an evanescent field 710 is generated at a surface of the edge portion 702. The head slider 701 is flown obliquely and accordingly, the edge portion 702 approaches a face of the disk and scatters light. The optical intensity of scattered light 711 is changed by presence or absence of a bit 712. The generated scattered light 711 is received by the light detecting element 703 after having passed through the waveguide path 704 provided at the vicinity of the edge portion 702 in the head slider 701. The light detecting element 703 carries out photoelectric conversion in accordance with the optical intensity of the scattered light 711. Thereby, information on the disk 708 is reproduced. According to the near-field optical head 700, the light source 705 and the lens 706 are integrated to the head slider 701 and therefore, the constitution becomes compact. Further, the constitution is suitable for mass production. (Embodiment 8) Fig. 12 is an outline constitution view showing a structure of a near-field optical head according to Embodiment 8 of the invention. According to the near-field optical head 800, an edge portion 802 similar to the above-described (refer to Fig. 2) is formed at a bottom face of a head slider 801. Further, a light detecting element 803 and a waveguide path 804 are provided at a vicinity of the edge portion 802 in the head slider 801. Further, a light source 805 and a waveguide path 806 are integrated to the head slider 801. A tapered face 807 is provided at a side thereof opposed to the edge portion 802. A flow path in a shape of a wedge film is produced by the tapered face 807 and a disk 808. Further, formation of the edge portion 802 is carried out by an etching treatment. The near-field optical head 800 is supported by a suspension arm (illustration is omitted) and is driven by a voice coil motor (illustration is omitted). Light 809 from the light source 805 illuminates the edge potion 802 after having passed through the waveguide path 806. Thereby, an evanescent field 810 is generated at a surface of the edge portion 802. The head slider 801 is flown obliquely and accordingly, the edge portion 802 approaches a face of the disk and scatters light. The optical intensity of scattered light 811 is changed by presence or absence of a bit 812. The generated scattered light 811 is received by the light detecting element 803 after having passed through the waveguide path 804 provided at the vicinity of the edge portion 802 in the head slider 801. The light detecting element 803 carries out photoelectric conversion in accordance with the optical intensity of the scattered light 811. Thereby, information on the disk 808 is reproduced. According to the near-field optical head 800, only the edge portion 802 can be illuminated by the waveguide path 806 and therefore, stray light entering the light detecting element 803 can be reduced. Further, the light source 805 is integrated to the head slider 801 and therefore, the constitution becomes compact. Further, the constitution is suitable for mass production. Further, a lens may be arranged in front of the guide path 806. Further, although according to the above-described embodiments, an explanation has been given of various means, members as well as structures in a limited way, they can pertinently be modified within a range where the skilled person can design. INDUSTRIAL APPLICABILITY As has been explained, according to the near-field optical head of the invention, the front end portion of the head is formed in a shape of an edge where two planes intersect with each other and therefore, the mechanical strength of the head is enhanced and the reliability of the head is promoted. Further, according to the near-field optical head of the invention, the front end portion of the head is formed in an edge shape in which at least one of the two intersecting faces is constituted by a curved face and a side where two faces intersect is provided with a curvature in a diameter direction of a medium. Preferably, the radius of curvature is set to five times or more of a bit width of the medium. Therefore, a signal in a direction orthogonal to a track does not constitute noise and an S/N ratio sufficient for practical use is provided. Further, according to the near-field optical head of the invention, one of the two faces forming the edge constitutes a bottom face of a slider and accordingly, there is no need of matching heights of a tip and a slider as in the case of forming the tip at the slider. Further, a sharpening process is dispensed with, the edge portion can be formed by etching and therefore, fabrication thereof is facilitated. Further, according to the near-field optical head of the invention, the light detecting element is arranged at an upper portion of the head and accordingly, the head becomes compact. Further, according to the near-field optical head of the invention, the light detecting element is provided at a vicinity of the head in the slider having the head and therefore, the head becomes compact and the light detecting efficiency of scattered light is improved. Further, according to the near-field optical head of the invention, the guide path is provided at a vicinity of the head in the slider having the head, the light detecting element is provided at the waveguide path and therefore, only scattered light from the edge can selectively be guided to the light detecting element and therefore, the S/N ratio is improved. Further, according to the near-field optical head of the invention, the metal film is provided over the entire or at a portion of the bottom face of the slider and the edge portion is formed by the metal film. Light can be reflected at the bottom face of the slider and therefore, stray light can be reduced. Further, the edge is formed by the metal film and accordingly, the scattering efficiency is improved. Further, according to the near-field optical head of the invention, the slider having the head is constituted by a material having transparency, the light source is arranged on the side of the slider relative to a medium and accordingly, the entire apparatus becomes compact. Further, according to the near-field optical head of the invention, the slider having the head is constituted by a material having transparency, the light source is provided at the slider and accordingly, the constitution can be made compact. Further, the constitution is suitable for mass production performance. Further, according to the near-field optical head of the invention, the slider having the head is provided with the light source and the waveguide path for transmitting light of the light source and accordingly, stray light entering the light detecting element can be reduced and therefore, the S/N ratio is improved.

Claims: A near-field optical recording arrangement comprising: a recording medium (1) for the recording of bits of information: and a near-field optical head (2) for reproducing said information recorded on said medium based on an intensity of scattered light of an evanescent field generated when a front end portion (22) of a head is made proximate to the medium at an interval of a distance equal to or smaller than a wavelength of light therebetween and light is illuminated to the medium, the front end portion of the head having the shape of an edge (23) formed by the intersection of two faces (24, 25) of the head, characterised in that the edge is microscopically provided with a first radius of curvature (Rt) lying in a plane orthogonal to said two faces, said radius being equal to or smaller than the shortest bit length of said bits. A near-field optical recording arrangement according to claim 1, wherein the two faces are two planes and the first radius of curvature lies in a plane orthogonal to said two planes. A near-field optical recording arrangement according to claim 1, wherein at least one (24, 25) of said two faces is curved, whereby said edge is provided with a second radius of curvature (Rn) wich is that of said curved face. A near-field optical recording arrangement according to claim 3, wherein the curved face (24) is that which faces the medium. A near-field optical recording arrangement according to claim 3, wherein the curved face (25) is that which lies orthogonal to the medium. The near-field optical recording arrangement according to any one of claims 3 through 5, wherein the second radius of curvature is set to be equal to or greater than five times as much as a width of said bits. The near-field optical recording arrangement according to any one of claims 1 though 6, wherein one of the two faces constitutes a bottom face of a slider. The near-field optical recording arrangement to any one of claims 1 though 7, wherein a light detecting element (504) is arranged at an upper portion of the head. The near-field optical recording arrangement according to claim 7, wherein a light detecting element (3) is provided at a vicinity of the head in the slider. The near-field optical recording arrangement according to claim 7, wherein a waveguide path (505, 605; 704; 804) is provided at a vicinity of the head and a light detecting element (504; 604: 703; 803) is provided at the waveguide path in the slider. The near-field optical recording arrangement according to any one of claims 7 through 10, wherein a metal film is provided over at least a portion of the bottom face of the slider and said edge is formed by the metal film. The near-field optical recording arrangement according to any one of claims 7 through 10, wherein the slider is constituted by a material having transparency and a light source (606; 705; 805) is arranged at a side of the silder opposite to that which faces the medium. The near-field optical according arrangement according to any one of claims I through 10, wherein the slider is constituted by a material having transparency and a light source (705; 805) is provided in the slider. The near-field optical recording arrangement according to claim 13, wherein a waveguide path (806) for transmitting light of the light source (805) is further provided in the slider.

Inventors: CHIBA NORIO, KASAMA NOBUYUKI, MITSUOKA YASUYUKI, NAKAJIMA KUNIO, NIWA TAKASHI, CHIBA, NORIO, KASAMA, NOBUYUKI, MITSUOKA, YASUYUKI, NAKAJIMA, KUNIO, NIWA, TAKASHI
Applicants: SEIKO INSTR INC, SEIKO INSTRUMENTS INC.
Application year: 1999
Main classification: G11B7
IPC codes: G11B7, G01N37, G01N13