Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
1999-05-21
2001-02-06
Epps, Georgia (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S318000, C359S320000, C359S251000, C359S254000
Reexamination Certificate
active
06185031
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an optical switching method and an optical switching apparatus.
Usually, the refractive index of light which relies upon the fact that incoming light to a certain substance goes out at a predetermined angle is inherent to the substance.
Various proposals have conventionally been made to use an external electric field to control the refractive index of light which is an inherent value of a substance to control the advancing direction of the outgoing light.
For example, in a “Thin film switch array” of Japanese Patent Laid-Open No. Sho 52-111739, a predetermined electric field is applied to a crystal substrate made of lithium niobate and having Ti diffused herein to lower the refractive index of the substrate to perform switching of the light path of reflected light of a predetermined wavelength. Also in a “Thin film optical switch” of Japanese Patent Laid-Open No. Sho 50-115547, a predetermined electric field is applied to a substrate made of Sr
0.75
Ba
0.25
Nb
2
O
6
to vary the refractive index of the substrate to perform switching of the light path of reflected light of a predetermined wavelength.
Another technique has been proposed wherein, if a voltage is applied to an organic material composed of an ultraviolet ray setting resin in which very fine particles of liquid crystal are dispersed and closed up, then the refractive index of light by the material varies, thereby varying the advancing direction of the outgoing light. This technique relies upon the fact that the direction in which liquid crystal molecules are arranged is varied by the voltage applied to the material.
It is also known that similar effects can be obtained where a photo-polymer having liquid crystal molecules on side chains, that is, ferroelectric liquid crystal (for example, the UCL-001 by Dai-Nippon Ink Industries, Co. Ltd.), is used.
However, in the method described above wherein a voltage is applied to an organic material composed of an ultraviolet ray setting resin in which very fine particles of liquid crystal are dispersed and closed up to vary the refractive index of light, the response time of the refractive index variation is less than 10 microseconds, that is, approximately several microseconds, and the response time of the refractive index variation where ferroelectric liquid crystal is used is approximately 10 to 40 microseconds.
The variation of the refractive index of light by a substance can be utilized for switching of a flow of a signal in an optical communication network or for information transmission in a liquid crystal display. In order to perform such switching or transmission operation rapidly, it is demanded to reduce the response time of the refractive index variation.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an optical switching method and an optical switching apparatus by which the response time of a variation in refractive index of light can be further reduced.
In order to attain the object described above, according to an aspect of the present invention, there is provided an optical switching method, comprising the steps of controlling an electric field to be applied to a light passing element made of a substance containing conjugated system electrons to vary the condition of electrons of the substance of the light passing element to vary the refractive index of the light passing element, controlling the outgoing direction of light introduced into the light passing element thereby to deflect the outgoing light from the light passing element, and introducing the deflected outgoing light so as to be irradiated upon a selected control object element (a light detector) to control the control object element.
According to another aspect of the present invention, there is provided an optical switching apparatus, comprising a light passing element made of a substance containing conjugated system electrons, electric field application means (a pair of electrodes) for applying an electric field to the light passing element, and a plurality of control object elements (a light detector) for being controlled by light irradiated thereupon, the electric field application means controlling the intensity and/or the direction of the electric field to be applied to the light passing element to vary the condition of electrons of the substance of the light passing element to vary the refractive index of the light passing element to deflect the outgoing direction of the light introduced into the light passing element so that the outgoing light of the light passing element is irradiated upon a selected one of the control object elements to control the control object element.
According to a further aspect of the present invention, there is provided an optical switching apparatus, comprising a light passing element made of a substance containing conjugated system electrons, electric field application means for applying an electric field to the light passing element, a plurality of control object elements for being controlled by light irradiated thereupon, and an optical modulation apparatus for modulating the intensity of the light to be introduced into the controlled object element, the electric field application means controlling at least one of the intensity and the direction of the electric field to be applied to the light passing element to vary the condition of electrons of the substance of the light passing element to vary the refractive index of the light passing element to deflect the outgoing direction of the light introduced into the light passing element so that the outgoing light of the light passing element is irradiated upon a selected one of the control object elements to control the control object element.
With the optical switching method and the optical switching apparatus, by simply applying an electric field to the light passing element and controlling the intensity and/or the direction of the electric field, a variation of the condition of electrons of the light passing element can be achieved rapidly. Consequently, the response time of the variation in refractive index of the light passing element can be further reduced when compared with the prior art described hereinabove. Further, the outgoing direction of light can be deflected rapidly to perform switching of irradiation of light upon the selected control object element, and consequently, control of the control object element can be performed rapidly.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements denoted by like reference symbols.
REFERENCES:
patent: 4879479 (1989-11-01), Frazier et al.
patent: 5157541 (1992-10-01), Schildkraut et al.
patent: 5290485 (1994-03-01), Gotoh et al.
Shingu Masataka
Sugimoto Tohru
Yamoto Hisayoshi
Epps Georgia
Kananen Ronald P.
Lucas Michael A.
Rader Fishman & Grauer
Sony Corporation
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