Electromagnetically induced transparency in semiconductors

Electromagnetically Induced Transparency (EIT) is a phenomenon in which the presence of a nonradiative coherence leads to destructive quantum interference, causing an otherwise absorbing transition to become transparent. As a spectroscopic tool, EIT can be used to probe for the existence of nonradiative coherences and to study their properties. Furthermore, EIT is of interest because it demonstrates the control of quantum coherence to dramatically change the linear and nonlinear optical properties of the system. Although EIT and related phenomena have been studied extensively in atomic systems, analogous effects have not been previously observed for interband transitions in semiconductors.; This dissertation presents experimental demonstrations of EIT using exciton and biexciton transitions in semiconductor quantum wells. Results are first presented which show that Rabi splitting of exciton and biexciton transitions is possible, though affected by many-body interactions. The ability to induce Rabi splitting is shown to be a prerequisite for establishing EIT in semiconductors. Numerical simulations of the optical Bloch equations indicate that EIT signatures can be observed using transient pump-probe spectroscopic techniques in which the pump is long and the probe is short relative to the dipole decoherence times. Observations of EIT due to three types of nonradiative coherence are presented and discussed: coherence between heavy-hole and light-hole valence bands, exciton spin coherence, and biexcitonic coherence.; In addition to demonstrating EIT in semiconductors, this dissertation discusses how these EIT experiments provide valuable information about the interplay of quantum coherence and many-body correlations in semiconductors. Studying the behaviors of the EIT signatures under various experimental conditions shows how the underlying nonradiative coherences are affected by exciton-exciton interactions. More importantly, the EIT experiments presented here indicate new types of quantum coherences induced by the many-body interactions themselves, a process without analog in noninteracting atomic-like systems. Specifically, this dissertation shows that in addition to bound biexciton states, even unbound two-exciton states can lead to quantum coherence through many-body correlations.