Spectroscopic Studies with Multiple Quantum Well Materials with Applications to Optical Signal Processing at Room Temperature

摘要

This program investigated the variety of laser induced optical processes in multiple quantum well and other nonlinear waveguide materials. These studies combined both theory and experiment. This work demonstrated the first optically pumped mode-locked A1(0.3)Ga(0.7)As/GaAs multiple quantum well (MQW) laser in external cavity. The MQW structure with a total thickness of 5 micrometers was grown by molecular beam epitaxy on a Si-doped GaAs substrate and was synchronously pumped by a mode-locked Kr+ laser (82) MGz) at 647.1 nm. The MQW laser emitted 10 ps pulses at 8085A with peak powers as high as 6W. The demonstrated MQW laser combines desirable properties of quantum wells with advantages of an external cavity, such as specific band-gap design with high beam quality and the possibility of intracavity tailoring of the laser beam. We also demonstrated the first mode-locked Si-doped bulk GaAs laser tunable over 300A range. Several experiments to measure the third order nonlinear optical susceptibility of MQW and other novel nonlinear materials were successfully completed. The first measurement of the third order nonlinear optical susceptibility of transpolyacetylene by third harmonic generation in thin films is reported. The measured susceptibility is chi (3 omega = omega + omega + omega) = 4 x 10 to the -10th power esu which is comparable to the magnitude of the large nonlinear susceptibilities measured in the polydiacetylenes.