ELECTROOPTIC IMAGING OF THE INTERNAL FIELDS IN A GAAS PHOTOCONDUCTIVE SWITCH

A technique has been developed that allows single-shot measurement of the electric field over an extended area. A LiTaO3 crystal, covering the entire active area of the GaAs photoconductive switch, coupled the surface field with the polarization of an optical probe pulse. When imaged onto a two-dimensional detector array, this system produced snapshots of the surface field profile with 200-ps time resolution and 3-mu-m spatial resolution. The technique was used to monitor the collapse of the electric field in the GaAs as it was switched with a lambda = 1.06 mu-m optical pulse. The switching speed and generation of field enhancements were found to be dependent on the illumination configuration and the electric field. In particular, the switching efficiency was found to decrease with increasing field.