OPTICAL SWITCHING IN CADMIUM TELLURIDE USING A LIGHT-INDUCED ELECTRODE NONLINEARITY

An optically controlled buildup and erasure of an electric field under the negative electrode in CdTe:In is reviewed both experimentally and theoretically. Below-band-gap impurity-absorbed light (850-920 nm) re sults in the buildup of a region of very high electric field (E approx imately 20 kV/cm) under the negative electrode. Illumination at wavele ngths above or near the band pp (800-840 nm) can erase the high electr ic fields. The writing and erasure of the field follow the illuminatio n pattern and can therefore be used, when combined with the electro-op tic or electroabsorption effects, for one- and two-dimensional infrare d spatial modulators with signal beams in the 900-1500-nm range. Switc hing times are a few hundred nanoseconds at moderate intensity levels (milliwatts per square centimeter). We demonstrate a one-dimensional l atching array with 170 line pairs/cm resolution, submicrosecond respon se, and 12-pJ/pixel switching energy. We also demonstrate a two-dimens ional infrared spatial light modulator, similar to the PRIZ, which use s this effect. The optically controlled electric fields are large enou gh for sizable Franz-Keldysh effects, and we demonstrate these effects in both one- and two-dimensional devices.