Abstract

The wealth of new phenomena which has been observed in semiconductor heterostructures displaying quantum confinement in a single dimension (quantum wells) has prompted efforts to fabricate structures which provide higher degrees of confinement [1]. Theoretical predictions of a strong reduction in scattering for structures which display confinement in two dimensions (quantum wires), and consequently a large mobility [2], also encouraged the efforts. Optical techniques have proved particularly suited to studying heterostructures [3]. However, definitive observations of many of the expected low dimensional phenomena have been hindered by fabrication difficulties. Nevertheless there has been some success with etched quantum wires, including the observation of a reduction in exciton-exciton scattering [4] and the observation of transient four-wave-mixing (TFWM) [5], which is particularly interesting because of its sensitivity to scattering processes. Although significant work on semiconductor quantum dots imbedded in a glass matrix has been performed, attempts at fabricating them in a semiconductor have faced similar difficulties as quantum wires.

© 1994 Optical Society of America