Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
2002-08-22
2004-09-14
Mulvaney, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064400, C428S702000, C430S270110
Reexamination Certificate
active
06790502
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel optically functional element, its production method and various applications using the same. In particular, the present invention relates to an optically functional element applicable to an optical switch with a large change in refractive index with temperature, temperature sensor and optical information recording medium, along with a production method for the same.
BACKGROUND ART
Optically functional materials, of which optical characteristics such as transmittance and refractive index change by exterior field such as light, temperature and electric field, have been used as elements such as optical switch, optical modulator, light amplifier, wavelength selective element, optical soliton element, optical information recording medium, temperature sensor and electro-optical element.
Examples of materials with a transmittance changeable by exterior field include such as photochromism, thermochromism and electrochromism materials. In these materials, transmittance can be changed reversibly by an application of light, temperature and electrical field, respectively, correspondingly to their intensity, and thus they are used as optical switch, temperature sensor, masking layer for optical information recording medium and the like by shielding transmitted light or controlling spot diameter of transmitted light. As examples of these materials, the following are known: Organic photochromism materials such as derivatives of triphenylmethan, azobenzene and spiropyran disclosed in JP-A-7-20600, organic or inorganic thermochromism materials such as N-salicylideneaniline, AgHgI
4
and Cu
2
HgI
4
, along with materials in which these materials are dispersed in dielectric materials having different refractive indices.
On the other hand, as examples of materials with refractive index changeable by exterior field, second or third order non-linear optical materials are known, of which refractive indices change at a part applied with laser or electric field. As second order non-linear optical materials, the following are known: Organic materials such as nitropyridine derivatives and methylnitroaniline (MNA) and inorganic dielectric materials such as KNbO
3
and LiNbO
3
, which have been used as optical switch, electro-optical element and the like. Third order non-linear optical materials include glass dispersed with semiconductor fine particles such as CuCl and CdS, which have been used as optical switch of light waveguide type wavelength selection element and light pulse generating element (See “Handbook of Optical Materials”: published by Realize Co., Ltd., 1992).
In addition, as materials with refractive index changeable with temperature, zinc based semiconductor materials such as ZnS and ZnSe and finely powdered PbS are known. Providing that amount of change in refractive index with temperature, &Dgr;n
T
, is expressed by the following formula:
Δ
n
T
=
&LeftBracketingBar;
Δ
n
Δ
T
&RightBracketingBar;
wherein,
&Dgr;n is amount of change in refractive index; and
&Dgr;T is amount of change in temperature
these materials have been reported to have &Dgr;n
T
from about 5.95×10
−5
/° C. to about 1.47×10
−4
/° C. (See Physics Report, Vol. 46, No. 12, December 1997).
Further, as non-linear optical materials, the following are known: Those using Co
3
O
4
and CoO as targets disclosed in JP-A-10-340482, amorphous metal oxides containing fine particles of Fe, Ni and Co disclosed in JP-A-5-224262 and substrates on which thin films of oxides of one or more elements of V, Cr, Mn, Fe, Ni, Co and Cu are formed as disclosed in JP-A-7-248516.
Since temperature sensor or device performing optical switching with temperature mainly works based on thermochromism switching as described above, amount of transmitted light varies. Therefore, they have not been suitable for a communication device in which such change gives unfavorable effects. Presently known devices made of materials whose refractive index changes with temperature have small change in refractive index and have been difficult to get sufficient change as switching or temperature sensor. Furthermore, these materials have response rate of refractive index with temperature in ms level, which is still slow in communication or light recording fields and thus have not been suitable to these applications.
Examples in the references of the above described “Physics Report” also required to be used as a dispersion in solvent due to powder form, which has made it difficult to be used as a thin film.
Furthermore, in optical switching also, these elements have had difficulty in characteristics control so as to have energy sufficient to raise change in refractive index or transmittance in these elements and to give incident laser light for stable output. The above patents do not disclose change in refractive index responsive to temperature, crystal particle size and crystal structure of oxide thin films.
Objectives of the present invention are to provide an optically functional element having large change in refractive index responsive to temperature change, its production methods and various applications using the same.
DISCLOSURE OF THE INVENTION
In an optically functional element with optically functional thin film on a substrate, the present invention is characterized in comprising at least one of the following: Said thin film consists of oxides and is composed of columnar crystal having average diameter of not larger than 13 nm, preferably not larger than 7 nm, said thin film consists of oxides and a change in average refractive index of 633 nm laser light from room temperature to 300° C. is not less than 2×10
−4
/° C., said thin film consists of oxides and is composed of columnar crystal inclined against said substrate surface, said thin film mainly consists of oxides of one or more types of Co and Fe having spinel structure and is composed of columnar crystal, and at least one type of Co and Fe of said thin film mainly consists of M
3
O
4
oxides including not less than one oxide of Si, Ti, Al, Te, alkaline metals and alkaline earth metals and is composed of columnar crystal.
The present invention is further characterized in a production method for an optically functional element to form optically functional thin film consisting of oxides on a substrate, wherein said thin film is formed by sputtering under reduced pressure of inert gas atmosphere having 3-15% by volume of oxygen.
The present invention is characterized in an optical switch equipped with a light receiver to receive light introduced from light source and an optically functional element having optically functional thin film to alter light pass of said light, wherein said optically functional element is consisted of the above described optically functional element.
The present invention is characterized in a temperature sensor equipped with a light receiver to receive light introduced from light source and an optically functional element having optically functional thin film to alter light pass of said light, characterized in that said optically functional element is consisted of the above described optically functional element.
The present invention is characterized in a substrate with information formed by pits and recording medium of optical information to provide output of said information by reflection light from light reflection film formed on said substrate, wherein said reflection film has, at its incident side of light, an optically functional thin film having refractive index changeable depending on incident light intensity and said thin film is consisted of the above described thin film.
An optically functional thin film formed in an optically functional element of the present invention, is formed on a substrate directly or via other layers, which is composed of fine particles with average particle diameter of not larger than 13 nm observed at film surface and its refractive index changes in response to own temperature change.
Hosaka Sumio
Kirino Fumiyoshi
Koyama Eiji
Naito Takashi
Nakazawa Tetsuo
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