Use of a pulsed laser to study properties of CdZnTe pixel detectors

We have investigated the utility of employing a short (<4 ns) pulsed laser with wavelength tunable between 600-950 nm as a tool for studying and characterizing CdZnTe detectors. By using a single mode optical fiber and simple optics, we can focus the beam to a spot size of less than 10 μm and generate the number of the excess carriers equivalent to a several MeV gamma-ray either at the surface or deep inside the sample. The advantages of this technique over use of a collimated X-ray or alpha particle source are strong induced signal, precise pointing, and triggering capability. As examples of using this technique, we present the results of measurements of the drift velocity, electron lifetime, and electric field line distribution inside CZT pixel detectors.