Optical and thermal finite-difference time-domain model for passively mode-locked surface-emitting lasers

摘要

The dynamics of ultrashort pulses generated by a monolithic passively mode-locked vertical cavity surface-emitting laser containing a multiple quantum well gain region and a single quantum well saturable absorber are studied. We introduce a self-consistent computational model based on the finite-difference time-domain method, which describes the complete dynamics of surface-emitting lasers. The model consists of a set of coupled equations that accounts for the interrelations among the electromagnetic field, material polarization, carrier density, and lattice and plasma temperatures. The material response is incorporated via the effective semiconductor Bloch equations. The thermal effects are included through two coupled equations that relate the lattice and plasma temperatures to the carrier-phonon scattering effects. A comparison of the results obtained with and without the inclusion of thermal effects clearly demonstrates the effects of plasma heating. Finally, we also investigate the interplay between various relaxation rates, namely, the carrier-phonon scattering rate and the rate of heat loss to the ambient heat sink, and their relative influence on the system dynamics.