Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
1999-05-06
2001-06-05
Epps, Georgia (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S281000
Reexamination Certificate
active
06243193
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a magneto-optical light modulator which modulates transmission of light. In particular, the invention relates to a magneto-optical shutter device, which is capable of switching transmittance in response to a variation in incident light intensity and which may be incorporated into a light computing system, an image forming system, or an optical image processing system.
2. Description of Related Art
In the field of magneto-optical devices, several magneto-optical components including a magnetic film deposited on a grooved surface of a substrate, and an image display device using the components, have been disclosed by the present inventor in Japanese Laid-Open Patent Publication Nos. 10-213785, No. 11-7626, No. 11-8120, and No. 11-14814. However, a magneto-optical modulator that utilizes a magneto-optical component having a magneto-optical effect and that exhibits a dependence on intensity of incident light has not been disclosed.
In the field of light modulators, optical switches or optical shutters, which are able to operate faster than known electric switching devices, are known. Such light modulators include nonlinear optical materials having large nonlinear effect, such as artificially fabricated semiconductors having a superstructure, or specific organic materials, in order to achieve operation under the reduced intensity of light.
When the nonlinear material is employed in an optical switch having a micro-resonator, transmittance of a light flux can be controlled in response to a variation of intensity of the light flux. This is referred to as a “light-to-light gate component” or “all-light gate component”. The light-to-light gate component can operate with a short switching time. For example, a light modulator having a nonlinear material, which has a laminated film-structure in which gallium arsenide (GaAs) semiconductor thin films and aluminum gallium arsenide (AlGaAs) semiconductor thin films are alternatively deposited with a pitch of no more than 10 nm, can operate with a switching time of 0.5 picoseconds.
A variety of devices such as logic devices and memory devices can be fabricated by assembling the light-to-light gate components. For example, a light computing system can be built using such components. Improvements in the switching speeds of the above-mentioned modulators is necessary to achieve a light computing system capable of operating at a high frequency.
Thus, there is a need for a magneto-optical light modulator that utilizes a magneto-optical film to perform high speed switching in response to variations in incident light flux.
SUMMARY OF THE INVENTION
The present invention provides a novel magneto-optical modulator, which can operate in response to variations in incident light intensity and which is capable of operating with a short switching time.
In embodiments of the invention, a magneto-optical light modulator is provided including a first polarizer arranged to receive an incident light flux and to transmit a polarized light flux; a transparent magneto-optical component arranged to receive the polarized light flux and to transmit a rotated polarized light flux; and a second polarizer arranged to receive the rotated polarized light flux. The transparent magneto-optical component includes a substrate with a textured surface substantially parallel to a major surface plane of the substrate. As used herein, the term “major surface plane” refers to a plane generally formed by one of two opposing sides of a substrate that have larger surface areas than other sides of the substrate. The substrate can include two opposing textured surfaces. Each textured surface includes features having a depth in a range of from about 0.1 &mgr;m to about 5 &mgr;m. The features can be substantially uniform in shape and size, and can be spaced periodically on the textured surface. Each feature includes a side surface that is not parallel to the major surface plane. A magneto-optical film between about 5 nm and about 200 nm thick covers at least a portion of the side surfaces.
In other embodiments, the substrate has a textured surface including a plurality of straight grooves spaced periodically in parallel with each other on the surface. Each of the plurality of grooves has a depth in a range of from about 0.1 &mgr;m to about 5 &mgr;m and a width in a range of from about 0.2 &mgr;m to about 2 &mgr;m.
In embodiments of the invention, an axis of the second polarizer, which corresponds to a plane of polarization, is oriented such that a transmittance of light flux by the second polarizer increases with an increase in incident light flux intensity directed at the first polarizer. In other embodiments, an axis of the second polarizer is oriented such that a transmittance of light flux by the second polarizer decreases with an increase in incident light flux intensity directed at the first polarizer.
In still other embodiments, the magneto-optical light modulator includes a light source which can emit a light flux whose intensity is modulated. The light source may emit a light pulse. Also, the modulated incident light flux may be provided by a plurality of light sources.
REFERENCES:
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patent: 5212446 (1993-05-01), Itoh et al.
patent: 5386313 (1995-01-01), Szegedi et al.
patent: 5612813 (1997-03-01), Damman et al.
patent: 5991075 (1999-11-01), Katsuragawa et al.
patent: 6055215 (2000-04-01), Katsuragawa
patent: 6072174 (2000-06-01), Togawa et al.
Epps Georgia
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
Seyrafi Saeed
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