Quantum Analysis of a Microcavity-Tuned Bloch Oscillator for Tunable Spontaneous Emission and Absorption of Terahertz Radiation; Final rept. 31 Aug 2006-30 May 2007

摘要

We investigate the spontaneous emission of radiation for a Bloch electron traversing a single energy miniband of a superlattice in an external homogeneous electric field subjected the influence of resonant microcavity and dephasing from an internal inhomogeneous electric field. The spontaneous emission for the cavity-enhanced Bloch electron probability amplitude becomes damped and frequency shifted due to the perturbing inhomogeneity when treated in a long-time, time-dependent perturbation theory relative to the Bloch- accelerated dynamics in the electrodynamic radiation field. The frequency shift is proportional to the diagonal matrix elements of the Hamiltonian for the perturbing inhomogeneity with respect to the instantaneous Bloch eigenstates, and the damping term is proportional to the off-diagonal matrix elements of the perturbing Hamiltonian with the instantaneous eigenstates summed to the final states as determined in a golden-rule like fashion. The resulting general theory is reduced for the specific cases of an abrupt and smoothly varying potentials but emphasis is given to the case of a 'comb' of Slater-Koster impurities with randomly distributed interface roughness at all lattice sites. From the Slater-Koster case, the relaxation approximation is developed where the damping term is considered to be a constant and the frequency shift is ignored. Analysis of total power shows that dephasing degradation effects are more than compensated for by enhancements derived by microcavity confinement.