Optical waveguides – Optical fiber waveguide with cladding
Reexamination Certificate
2000-01-21
2001-03-27
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
Optical fiber waveguide with cladding
C385S117000
Reexamination Certificate
active
06208789
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a scanning-near-field-microscope, a probe utilizing near-field-optics, a method of manufacturing it, and a probe-type memory.
BACKGROUND ART
In recent years, utilizing a SNOM (Scanning-Near-Field-Optical-Microscope) realizing formation of an ultra resolving power image exceeding the limitation of an optical wavelength, researches are made to develop a high-density memory (SNOM-type memory) of 60 Gbit/in
2
−1 Tbit/in
2
passing the limitation of the conventional optical or magnetic recording performance.
To achieve the generation of the ultra resolving power image by near-field-optics, it is necessary to utilize an electromagnetic field called an evanescent field. In the SNOM-type memory, as a method of generating and detecting the evanescent field, an optical fiber probe and a hollow probe made of a dielectric substance are usually used. These probes have an end part at its tip having a length shorter than the wavelength of light that is incident thereon. The light leaves the probe from the end part as the evanescent field. It is known that the resolving power of the probe is almost equal to the length of the end part. The ultra resolving power image can be obtained by utilizing such a probe.
Accordingly, as the probe for use in the SNOM-type memory intended to obtain high-density recording, it is necessary to optically form an aperture so designed that the aperture has a diameter almost equal to a required resolving power. The intensity of the light leaving the tip of the probe is another factor determining a signal quality (S/N) and recording density. Thus, in the probe for use in the high-density memory, it is important to allow the incident light to reach the tip of the probe without the incident light leaking out from the probe.
Research has been hitherto made to prevent light from leaking out from the probe by forming a thin metal film on the outer surface of the probe. The use of a semiconductor laser is most favorable as the light source of the high-density memory. The wavelength of the semiconductor laser is 635 nm, 650 nm, 780 nm, and 830 nm which are more than 600 nm. Therefore, as the thin metal film covering the probe, a material having a high reflectivity for light with a wavelength more than 600 nm is desired. As the thin metal film having a high reflectivity for the light with the wavelength more than 600 nm, gold (Au) and copper (Cu) are described in Japanese Patent Application Laid-Open Publication No.8-94649. It is a well-known fact that Au and Cu indicate a high reflectivity for the light with the wavelength more than 600 nm as described in “New Edition of Table of Physical constants, table 7.1.2.3. P.172” or the like.
However, in an experiment in which the Au film having a high reflectivity is formed and light emitted by an He—Ne laser (632.8 nm) was incident on one end of the probe, the incident light was unable to reach the tip of the probe without the incident light leaking out from the probe. Thus, the intensity of the light at the tip of the probe is remarkably reduced, and the signal quality (S/N) is inferior. Accordingly, the experiment has revealed a problem that the probe is incapable of accomplishing high-density recording.
DISCLOSURE OF INVENTION
As a means for solving the problem, it has been found by the present invention that a probe that will be described below is effective.
It is an object of the present invention to provide a probe comprising a core having a first end part on which light from a light source is incident and a second end part with a diameter smaller than a wavelength of the incident light and a cladding covering the core, wherein a light-intercepting part having a thin nitride film made of at least one nitride selected from titanium nitride, zirconium nitride, and hafnium nitride is formed on a surface of the core at least at the second end part side except the first and second end parts.
The probe shows a high reflectivity for light with a wavelength of longer than 600 nm and prevents light from leaking out therefrom. Accordingly, it is possible to provide the probe that reduces the intensity of the light at the tip thereof in a small degree.
Further, it is an object of the present invention to provide a probe comprising a cylindrical body having a first aperture part on which light from a light source is incident and a second aperture part with a diameter smaller than a wavelength of the incident light, wherein a light-intercepting part having a thin nitride film made of at least one nitride selected from titanium nitride, zirconium nitride, and hafnium nitride is formed on a peripheral surface of the cylindrical body at least at the second aperture part side except the first and second aperture parts.
The probe shows a high reflectivity for the light with the wavelength of longer than 600 nm and prevents the light from leaking out therefrom. Thus, it is possible to provide the probe that reduces the intensity of the light at the tip thereof in a small degree.
Further, according to one embodiment, in a probe a thickness of the thin nitride film is 10 nm or more and 1000 nm or less.
That is, the film of titanium nitride, zirconium nitride, and hafnium nitride indicate a high reflectivity respectively for light with the wavelength of longer than 600 nm and can cover the probe uniformly in the thickness of 10 nm or more. Further, because they have excellent adhesive property, it is possible to cover the probe up to a thickness of 1000 nm without film peel. Moreover, it is preferable to set the thickness of the film of the titanium nitride, the zirconium nitride, and the hafnium nitride to 1000 nm or less to securely obtain a clearance for preventing a recording medium and the probe from colliding with each other.
Further, according to one embodiment, in a probe the light-intercepting part has a thin metal film made of one metal selected from titanium, zirconium and hafnium in contact with the core and the thin nitride film formed on the thin metal film and made of a nitride of the thin metal film.
By forming a two-layer construction having a thin nitride film and a thin metal film selected from at least one of titanium nitride/titanium, zirconium nitride/zirconium and hafnium nitride/hafnium, the stress of the thin nitride film can be relaxed and the adhesive property thereof can be improved. Thus, even when the intensity of incident light is increased, the probe has no film peel and a low degree of reduction in the intensity of the incident light at the tip thereof.
Further, according to one embodiment, in a probe a thickness of the thin nitride film is 10 nm or more and 1000 nm or less; and a thickness of the thin metal film is 10 nm or less.
In the probe, the film of the titanium nitride, the zirconium nitride, and the hafnium nitride indicate a high reflectivity respectively for light with the wavelength of longer than 600 nm and can cover the probe uniformly in the thickness of 10 nm or more. Further, because they have excellent adhesive property, it is possible to cover the probe up to a thickness of 1000 nm without film peel. Moreover, it is preferable to set the thickness thereof to 1000 nm or less to securely obtain a clearance for preventing a recording medium and the probe from colliding with each other. When the thickness of the thin metal film is 10 nm or less, the reflectivity of the light-intercepting part is hardly affected by the thin metal film and the adhesive property of the thin nitride film can be improved.
In a method of manufacturing a probe, according to the present invention, including a light-intercepting part having the thin metal film and the thin nitride film, the thin metal film and the thin nitride film are successively formed without exposing the surface of the metal film to an oxygen gas.
According to the method of manufacturing the probe, by successively forming a two-layer construction having a thin nitride film and a thin metal film selected from at least one of titanium nitride/titanium, zirconium nitride/zirconium and hafnium nitrid
Morrison & Foerster
Palmer Phan T. H.
Sharp Kabushiki Kaisha
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