Dynamic information storage or retrieval – Detail of optical slider per se
Reexamination Certificate
2001-05-07
2004-04-20
Cao, Allen (Department: 2652)
Dynamic information storage or retrieval
Detail of optical slider per se
Reexamination Certificate
active
06724718
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a near-field optical head capable of reproducing and recording high-density information using near-field light. The present invention also relates to a method of manufacturing the near-field optical head.
BACKGROUND INFORMATION
In recent years, a rapid development on both aspects of the hardware and the software is accomplished in the field of the information appliances and the amount of information to deal with keeps on growing drastically therewith. With regard to the information storage apparatus as one of the information appliances (HDD in particular), a rapid shift to high-density recording goes along currently in such a way that the recording capacity per unit area in recording medium increases by 60 percent in annual rate. Therefore, a further miniaturization is desired in the size of one record unit (bit) recorded and reproduced on a recording medium.
For recording or reproducing in a minute region, an apparatus for observing the minute region of a nanometer order on the surface of the sample or an application of the scanning probe microscope represented by scanning tunnel microscope (STM) or an atomic force microscope (AFM) is becoming an object of public attention. SPM scans the probe having a sharpened tip over the surface of the sample, while observing an interaction such as the tunnel current generated between the probe and the surface of the sample or the force between the atoms so as to obtain an image of a certain resolution depending on the tip configuration of the probe.
For performing a high density recording of a recording medium, the method of recording and reproducing with the use of light in comparison with magnetism has an advantage of enabling a high-density recording along the tracking direction (radial direction of the recording medium). Thus, the application of the near-field optical microscope viewing by light is expected as a promising matter especially among SPM.
The near-field optical microscope deals with an interaction produced between the near-field light generated on the surface of an inspection sample and the probe as an observation subject so as to be able to observe the minute region of the sample surface. The principle of the inspection approach is described in detail hereinafter.
The near-field light is generated by irradiating propagating light onto the surface of the inspection sample. Since the near-field light is generated only in a highly adjacent area on the surface of the inspection sample, the sharpened tip of the probe is approached closely to the surface of the inspection sample within a distance equal to or less than &mgr;m so as to scatter the near-field light generated from the tip of the probe. The scattered light is guided through a small aperture of the tip of the probe and processed by a conventional detection process of a transmitted light. Thus, the limitation of the viewing resolution of the conventional optical microscope is broken through and so the observation of a minute region by light becomes possible. Furthermore, a light of great intensity is introduced into the probe toward the inspection sample to generate a near-field light of high energy density in the minute aperture of the probe. By means of this near-field light, a local modification of the construction or the properties of the sample surface is also made possible. As described above, a realization of optical memory recording with high-density is thought to be possible by means of the application of near-field optical microscope.
In the architecture of the optical memory recording apparatus using such a near-field light, the probe is the most important part because it has a minute aperture acting as a recording and reproducing optical head. As an example of a probe having a minute aperture, as for instance described in U.S. Pat. No. 5,294,790, a cantilever-type photoprobe is proposed comprising an aperture penetrating through a silicon substrate by means of semiconductor manufacturing technology of photolithography or the like, an insulation film formed on one side of the surface of the silicon substrate and a cone-shaped light waveguide layer formed on the insulation film in the opposite side of the aperture. In this cantilever-type photoprobe, an optical fiber is interposed into the aperture so that the light can be transmitted through the minute aperture part which is formed by coating a light waveguide layer with a metal film except for the tip portion. Consequently, it is made easy to manufacture the aperture part.
Furthermore, an application of the planar probe without sharpened tip like the above-mentioned probe is proposed (T. Yatsui et al., “Readout capability of a planar apertured probe for optical near-field memory”, NFO-5, 115, Shirahama, Dec. 10, 1998). The planar probe is the one which is provided with an aperture of reverse pyramid structure on silicon substrate by means of anisotropic etching and in particular the vertex of the aperture is perforated with a diameter of several nm to form an aperture part. A plurality of such planar probes can be made simultaneously as a lump on a same substrate by semiconductor manufacturing technology, namely making an array of the planar probes is easy and in particular the planar probe has an advantage of utilizing as a suitable optical head for recording and reproducing the optical memory using near-field light. As an optical head using this planar probe, a head having a planar probe provided on the flying head used in a hard disk drive is proposed (Nikkei Electronics, Mar. 10, 1997 issue). The flying head is conventionally designed to fly by aerodynamic design keeping a spacing of 50-100 nm above the recording medium. With the use of this flying head, keeping the head and the recording medium in an extreme proximity (positional relationship) and forming a minute aperture in the flying head at the recording medium side, it becomes possible to generate near-field light. Therefore, high-density recording and reproduction by light is thought to be possible.
On realizing the optical information memory apparatus using near-field light, the utility value of the apparatus in itself is enhanced if the device in itself is made small and slim. For making the device small and slim, it is considered suitable to adopt a structure in which the light propagated in parallel with the recording medium is turned to a direction perpendicular to the medium and the aperture with the aid of optical components. However, with this structure, the head in itself becomes large and heavy due to the combination of optical components and results in a problem that the positioning accuracy and the response characteristics is deteriorated.
In addition, when a light is launched into the aperture by means of a light waveguide path such as an optical fiber, the intensity of the near-field light emitted from the aperture becomes small resulting in problems that the recording and reproducing rate is decreased and that the reliability of the information recorded and reproduced is deteriorated. As for this problem, since the light emitted from the light emitting edge of the light waveguide path is propagated spreading its width, and so the spot diameter of the light becomes large in accordance with the distance from the emitting edge. Then, the intensity of the light irradiated on the aperture is decreased and so is reduced the intensity of the near-field light for recording and reproducing. As a result, because the ratio of light intensity responsive to the information (S/N), a problem is generated that the recording and reproducing rate or the reliability of the information is deteriorated.
SUMMARY OF THE INVENTION
Therefore, a first near-field optical head according to the present invention comprises a slider supported by a load applying suspension arm for acquiring a flying force by means of a relative motion to a recording medium to make a spacing between the recording medium in accordance with a balance between the load and the flying force, a minute
Ichihara Susumu
Kasama Nobuyuki
Kato Kenji
Mitsuoka Yasuyuki
Niwa Takashi
Adams & Wilks
Cao Allen
Seiko Instruments Inc.
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