Optical Microstructures and Their Application to SpontaneousEmission Inhibition and Semiconductor Micro-Lasers (ResearchInitiation Award)

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An experimental research program is proposed to study inhibition of spontaneous emission in semiconductors using micro dielectric structures and to explore various realizations of semiconductor micro-lasers with microscopic ring cavities. The inhibition of spontaneous emission is of great interest because of its potential application to low- threshold lasers. We showed recently theoretically that the spontaneous emission rates of excitons in a semiconductor can be drastically reduced by embedding a thin layer of the semiconductor in low- refractive-index materials. An experimental study of this effect is proposed. The experiment will involve time-resolved measurement of excitonic decay in thin GaAs or InP quantum wells, or Yb-doped semiconductors, surrounded by materials of low refractive indices. Later, similar studies will be extended to wire-like dielectric structures. The microstructures required will be fabricated via a selective- etching technique. The same technique can be used to fabricate semiconductor micro-ring lasers, which were recently demonstrated to have low (optically pumped) thresholds. A good way to obtain output from such lasers, however, has not been achieved. An experiment is proposed to investigate the coupling of such lasers to waveguides as an output coupling method. Various geometries and active layers will be explored to determine the optimal relaization of such lasers.