Short-Pulse Effects in Fir Optical Saturation - Shallow Donors in Silicon

Optical saturation experiments are widely used to determine the lifetime T1 of photoexcited states. Unfortunately, such experiments require the simultaneous knowledge of the phase relaxation time T2 and an absolute calibration of the light intensity I in the sample, rendering the analysis of such experiments hazardous. The present contribution illustrates how this problem can be solved by using free electron lasers like FELIX yielding trains of short pulses instead of quasi-cw radiation