Picosecond transient optical phenomena in a-Si:H

Abstract With the advent of ultrafast lasers, powerful techniques have become available for directly studying extremely fast relaxation processes in solid rather than learning about them indirectly from steady state experiments. In this paper we review the application of the “pump and probe” technique to study electronic relaxations in a-Si:H. The method is based on producing an excited state in the material by the “pump” pulse and measuring the photoinduced changes in transmission ΔT and reflection ΔR by the “probe” pulse which is delayed by a known time interval with respect to the pump pulse. From these measurements we obtain information about the time dependence of the optical constants and consequently about the decay of the excited state.