Semiconductor Cavity QED

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This project builds on the breakthrough observation of accelerated decay (Purcell) of the resonant near-field coupling between two "oscillators" -- one the typical gain of a single semiconductor quantum well (InGaAs) and the other the very strong absorption of an array of metallic (silver) split ring resonators with very large dipole moments. The observation of this coupling is possible because of the giant vacuum field produced by the split ring resonator having a mode volume, V, a thousand times smaller than the minimum V for a photonic crystal slab cavity fabricated in a dielectric (silicon or GaAs). One can predict from the quantum well results that one should even be able to see coupling between such a resonator and a single stationary quantum dot -- the principal goal of this project -- thus opening a new regime for light-matter (resonator-emitter) interaction. Usually, Purcell enhancement (proportional to Q/V) is achieved in a dielectric cavity of very high quality factor, Q. Thus, enhancement occurs only for an emitter lying within the very narrow range of frequencies of the cavity peak. In contrast here, the Q of the split ring resonator is only of order 10; nonetheless, the Purcell enhancement is still large because of the metallic resonator's very tiny mode volume. Consequently, emitters with transitions lying anywhere within the very broad resonance are subjected to a very large vacuum field and have their spontaneous emission accelerated, resulting in overlap of their radiatively broadened spectra.The results of fundamental atomic and semiconductor cavity QED research have had lasting impact on semiconductor laser technology. A specific ongoing example is the development of the vertical-cavity surface-emitting laser (VCSEL) pioneered by a graduate from this group. Single quantum dot cavity QED enables nanoscience to go beyond traditional nonlinear optics and laser physics into a new regime with dynamical processes and active devices now involving quantum dots and photons taken one by one. This research on quantum optics in monolithic solid-state cavities would continue to forge new links between the AMO and nanophotonics communities begun by the observation of strong coupling reported in a highly-cited Nature article.