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 lea ds to the creation of a fast all-optical polarisation switch by using a cir cular polarised excite and a linear polarised probe pulse. It is demonstrat ed that the operation of the switch is dependent on the sense of circular p olarisation of the probe. An optically induced birefringence is identified.