Carrier transport, ultrafast spin dynamics and polarisation switching in InGaAsP multiple quantum wells

Excitonic optical nonlinearities are exploited in room temperature InGaAsP multiple quantum wells to determine the in-well carrier mobilities and spin relaxation processes. The picosecond time scale of the spin relaxation leads to the creation of a fast all-optical polarisation switch by using a circular polarised excite and a linear polarised probe pulse. It is demonstrated that the operation of the switch is dependent on the sense of circular polarisation of the probe. An optically induced birefringence is identified.