Abstract

In biased quantum wells, non linear absorption near the band edge can arise from excitonic saturation, and from screening of the bias field by photogenerated carriers (which leads to absorption changes through the quantum-confined Stark effect.^[1] The speed of response of both these phenomena depends on carrier escape rates from the quantum wells. By performing pump-probe experiments on single quantum well waveguide samples, we have been able, first of all to separate these two nonlinear absorption phenomena, and, secondly, to time resolve both electron and hole emission from the wells. Hole emission has previously been very hard to observe, and this new understanding is important for the non linear mechanisms, for design of quantum well switching devices, and for the physics of carrier tunneling in quantum wells.

© 1992 IQEC