Chapter 5 Nonlinear Optical Properties of Multiple Quantum Well Structures for Optical Signal Processing

Abstract

This chapter discusses the nonlinear optical properties of multiple quantum well structures for optical signal processing. Two properties of quantum wells that are relevant for nonlinear optical devices are: first, quantum wells show optical absorption saturation associated with the remarkably distinct room-temperature excitonic resonance. Second, they show a large electricfield dependence of the absorption, both associated with the excitonic transition and also directly with the transition between two-dimensional subbands. All these effects are seen near the optical absorption edge. The work reviewed here is primarily, from recent experiments on GaAs/AlCaAs multiple quantum well structures (MQWS). The chapter discusses the linear absorption in MQWS with a particular emphasis on room-temperature effects. It presents the measurements of nonlinear optical effects in MQWS, including absorption saturation and four-wave mixing. Further, the experimental and theoretical studies of electroabsorption in MQWS are reviewed, and the example of a new category of devices that exploits both the absorption saturation and electroabsorption is discussed.