Abstract

We have observed that near bandgap illumination (λ ~ 0.8-0.95 µm) of a CdTe:In crystal under an applied voltage alters the uniform electric field distribution and resuits in a high electric field region near the negative electrode. Although a similar effect has been reported for BSO, GaAs, and other photorefractive crystals, the behavior in CdTe differs in several aspects. We have measured the time evolution, voltage, and the intensity dependence of the magnitude and the width of the high field region. This effect is used in a transverse electrooptic modulator where a near IR (0.8-0.95-µm) beam from a GaAs laser or an incoherent source, shone through a transparent ITO electrode, modifies the electric fields, and hence the birefringence below the electrode. The polarization state of a longer wavelength signal beam is altered and accordingly routed by a polarizing prism. We have observed a very high sensitivity to the control beam (I_control ~ 10 µW/cm²) and have been able to demonstrate low loss (–0.5 dB corrected by the reflection losses), high contrast (>10:1), and routing of a signal beam (λ~ 1.5 µm). We have measured a latch-type switching time of 40 µs at higher intensities with a long dark decay time. Factors concerning the integration of this device into an array are being examined and are reported on.

© 1989 Optical Society of America