Stability and Tolerance to Optical Feedback of Quantum Dot Lasers

This report results from a contract tasking Universite Libre de Bruxelles as follows Quantum dot QD lasers have attracted a lot of attention because of their low threshold currents, low line width enhancement factors, and temperature insensitivity. Although the self-assembled dots have provided an enormous stimulus to work in this field, there remain a number of critical issues involving their growth and formation greater uniformity of size, controllable achievement of higher quantum dot density, and closer dot-to-dot interaction range will further improve laser performance. Better understanding of carrier confinement dynamics and capture times, and better evaluation of loss mechanisms, will further improve device characteristics. Because of the large variety of QD lasers currently tested in laboratories, there are several obstacles in the characterization and modeling of these devices that need to be overcome. A delay-differential equation model of a passively mode-locked quantum-dot laser originally proposed by Vladimirov and Turaev has been used recently by AFRLRYDP to simulate asymmetric pulse intensities which have been observed experimentally. The model equations for the passively mode-locked QD laser include delay and exponential nonlinearities and are too complicated for analytical studies. This has motivated very recently investigations of simpler experimental set-ups as turn-on experiments, the optically injected laser or the laser subject to a delayed optical feedback. In collaboration with N. Usechak and V. Kovanis at AFRLRYDP and the experimental group of L.F. Lester University of New Mexico, we propose a multi-disciplinary approach of the stability of QD lasers subject to optical feedback. The group of T. Erneux at the Universite Libre de Bruxelles ULB will be responsible for the modeling and analysis of rate equation models. Numerical simulations will be shared by the Brussels and AFRL groups.