[en] A method involving the generation of charge carriers by nuclear particles (α-particles or γ-rays) and measuring the charge collection efficiency or counting rate while simultaneously exciting with monochromatic light has been used for the study of deep traps in CdTe intended for semiconductor detectors. The electric field distribution may be determined by looking at the shape of the pulse. A way of directly observing the electric field was to utilize the electro-optic effect of CdTe, which has the zincblende structure, by viewing the optical transmission between crossed polarizers as a function of applied bias and time. These techniques have been applied to CdTe but can be applied to other materials. (U.S.)