Optical: systems and elements – Optical modulator – Light wave temporal modulation
Patent
1993-12-16
1996-05-28
Epps, Georgia Y.
Optical: systems and elements
Optical modulator
Light wave temporal modulation
G02F 103
Patent
active
055217435
ABSTRACT:
A photon-counting spatial light modulator that has an avalanche photodiode structure and is designed to operate in Geiger mode is sensitive to a single photon of light. An avalanche photodiode having an applied electric field is excited by an optical wave comprising one or more photons whose energies exceed the band-gap energy of the photodiode material. This localized electrical excitation alters the refractive index of the material through various effects, most notably the transient thermo-optic effect and the photorefractive effect. A second optical wave is incident during or shortly after the electrical excitation, and comprises photons whose energy is less than or nearly equal to the band-gap energy. This second optical wave is then used to read out the avalanche-induced variation in refractive index. This read out is most effective when the avalanche photodiode structure has partially reflective front and back surfaces and therefore forms a Fizeau interferometer in which the variation in refractive index causes localized variations in reflectivity.
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Bennett Glenn T.
Holmes Richard B.
Bey Dawn-Marie
Epps Georgia Y.
Field Harry B.
Kahm Steven E.
Montanye George A.
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