The PI's of this proposal have recently demonstrated a record, room temperature optical nonlinearity with picosecond response time in mercury telluride. They propose to continue their study of nonlinear optical processes in semiconductor, with the specific goal of achieving even larger and faster optical nonlinearities for applications such as signal processing and far infrared generation. Their effort will combine theory and experiment. The experiments will involve nonlinear optical mixing with carbon dioxide lasers. The following projects are proposed: 1. Study the effect of band structure tailoring in superlattices. Our theories have shown that electronic processes in superlattices can exhibit large nonlinear optical effects. 2. Explore hybrid optical electrical processes, especially effects near the thresholds of the Gunn instability an impact ionization. An initial experiment has demonstrated optically triggered flip-flop in germanium. 3. Continue our work on zerogap semiconductors, including far infrared generation and optimization of the large optical nonlinearity. 4. Continue studies of nonlinear optical effects due to impurity levels in semiconductors. 5. Use nonlinear optical methods to characterize superlattice structures. Specifically, the characteristic relaxation mechanisms of superlattices will be probed by four-wave mixing experiments.
