ABSTRACT
This chapter describes the use of ultrashort-pulse lasers to study in-well and cross-well transport in multiple quantum well (MQW) semiconductors via excitonic optical nonlinearities. Both absorptive and refractive optical nonlinearities resulting from the optical generation of carriers can be employed to detect carrier dynamics on time scales well beyond the capabilities of electronics. Excitons have played an important role in carrier transport studies of MQW semiconductors. This quantum-confined Stark effect (QCSE) is unique to quantum wells, because of the prominent room temperature excitonic absorption structures and due to the fact that wells prevent rapid ionisation of the excitons in an electric field. Pump probe measurements monitored both exciton saturation and the dynamical QCSE in order to unravel the dynamics of the various carrier types. Carrier diffusion and mobilities have been studied in bulk and quantum well semiconductors using the transient grating technique in a number of different configurations.
