Quantum Optical Studies of Semiconductors.
Final rept. 15 Jan 93-14 Apr 96,
MICHIGAN UNIV ANN ARBOR DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
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There have been two primary objectives during the current program 1 The development and application of nonlinear laser spectroscopy to the study of excitation dynamics near the band edge of semiconductor heterostructures 2 The understanding of pump noise suppression for production of number squeezed states of the laser field from quantum well lasers for application to low noise experiments. Our progress in the study of GaAs structures has relied on an approach employing both high resolution frequency domain and picosecondfemtosecond coherent nonlinear spectroscopy. We have obtained new understanding of the dynamics and energy level structure associated with excitons particularly as these properties are affected by disorder and magnetic fields. Our work in bulk GaAs shows that the nonlinear response at moderate densities is due to dynamic exciton-exciton interactions which lead to a nonlinear response proportional to the effective exciton-exciton collision cross section. These experiments have been paralleled with new understanding regarding the role of quantum coherences in the optical properties of these systems. Our studies of noise reduction below the standard quantum limit have resulted in our achieving 95 of the theoretically predicted limit for number state squeezing in a quantum well laser 4.5 dB below shot noise, 5.9 dB corrected to the facet. We have also made a preliminary demonstration of an application to semiconductor spectroscopy in the study of the Urbach tail in a GaAs multiple quantum well structure.
- Solid State Physics