Multiple Quantum Well Electrically/Optically Addressed Spatial Light Modulator
Patent, Filed 30 Sep 97, patented 1 Dec 98
DEPARTMENT OF THE NAVY WASHINGTON DC
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A multiple quantum well spatial light modulator combines both optically addressed and electrically addressed portions on a single wafer. The electrically and optically addressed portions may be physically distinct or combined. To fabricate the modulator, a portion of an optically addressed multiple quantum well spatial light modulator is configured as an electrically addressed portion by pixellating that portion of the multiple quantum well wafer. The frequency of the applied voltage to the electrically addressed portion is increased such that the voltage switches faster than both the dark and illuminated screening time. The electrically and optically addressed portions may be combined or positioned side-by-side. The spatial light modulator has applications in a wide variety of low-cost, high performance pattern recognition systems. In one system, a first infrared beam impinges the electrically addressed portion of the modulator and picks up the pattern electrically written thereon i.e., the template image. A second infrared beam impinges the optically addressed portion of the modulator and picks up the pattern written thereon by a white light writing beam i.e., sample image. The first and second infrared beams then pass through a lens, where the beams are Fourier transformed in the plane of an optically addressed spatial light modulator OASLM. The correlation hologram formed on the OASLM is read out by a third infrared beam and detected using a photodiode array. In a second system, the lens and OASLM are replaced with a parabolic reflector which reflects the first and second infrared beams onto the optically addressed portion of the modulator.
- Electrooptical and Optoelectronic Devices