Quantum coherence and interference effects in doped crystals and semiconductor quantum wells for reduced absorption and lasing without population inversion

This dissertation explores the effects of using one laser field to create quantum coherence and interference in doped crystals and semiconductor quantum wells. In doped crystals, lasing withput population inversion (LWI) is numerically studied both in steady state and in the transient regime to help understand the dynamical behavior of the LWI process by solving the complex coupled density matrix equations. The effects of the large transition linewidths resulting from inhomogeneous broadening in doped crystals are shown to reduce the overall gain. Zeeman-split ground state energy levels coupled by a microwave field in Ruby are shown to exhibit reduced absorption with the microwave on where the effect of the probe laser linewidth is included by taking the convolution of the resulting response with the probe laser lineshape function. The results do agree with experiments.; In double quantum wells, a three subband model in which two tunneling-split subbands are coupled by a dc-field is studied. The importance of the dc-field in establishing the quantum coherence and interference is shown. The coulomb renormalization of electron kinetic energy is included through the Hartree-Fock approximation and the effects of excitonic renormalization are included by using the Ladder and Phase approximations.