Associate 1995-96

Shun Lien Chuang

Electrical & Computer Engineering

Modeling of Strained Quantum-Well and Quantum-Wire Lasers

Professor Chuang plans to develop a complete theoretical model and computer programs for the optical gain of strained quantum-well and quantum-wire lasers. More recent experimental results by various groups on novel quantum-wire lasers and II-VI compound semiconductor blue-green lasers, which were successfully demonstrated within the last two years, show that the many-body Coulomb attractions between the electrons and holes on the optical gain play a very important role for the laser operation. Yet little theoretical work has been performed which can be compared with the experimental observations. The difficulty is due to the complicated nature of the many-body interactions in a densely populated semiconductor medium with electrons and holes, which interact via the Coulomb force in the presence of phonons. The complex valence band structure of the semiconductor quantum wells and quantum wires makes the theoretical modeling challenging.  The research goal is to develop a new and complete theoretical model for the excitonic gain, which can be used to compare directly with the experimental observations. Many-body effects such as screening, bandgap renormalization, and modified gain spectrum taking into account strain effects will be evaluated.

A systematic theoretical study of the exciton-photon interaction taking into account exciton-phonon, exciton-exciton, and exciton-free carrier scattering broadening as a function of temperature will be compared with the temperature-dependent optical gain to identify the physical processes for the gain. Professor Chuang's theoretical models will be compared with experimental data from various groups, including his own. His research laboratory at Everitt Lab has the equipment to measure the optical gain spectrum and characterize the semiconductor lasers for the proposed work.

The impact of this research will be the development of a new and complete theoretical model and computer programs for strained quantum-well and quantum-wire lasers. It has the potential to design high-performance semiconductor lasers with ultrahigh-speed modulation and stable temperature operation for coherent optical communications and optical recordings. It will be fundamentally important for optoelectronics research.