Ultrafast all-optical switching using a semiconductor optical amplifier

On the basis of numerical experiments, we discuss how a semiconductor optical amplifier in a Sagnac interferometric arrangement can be used for switching 200 fs pulses. The switching principle is based on gain and index saturation dynamics on a sub-picosecond timescale. The model accounts for bi-directional propagation of ultrashort optical pulses through the amplifier as well as free-carrier and two-photon absorption.