Abstract

We develop a detailed theoretical description of passively mode-locked semiconductor lasers [1] based on saturable absorber and compare it with experimental results. Our approach is based on a coarse grained Traveling Wave Model approach [2] and a recently developed analytical time-domain susceptibility of semiconductor quantum wells [3]. Under the approximation of intraband quasi-equilibrium, our model accounts for the dispersion of gain, absorption and refractive index and self-phase modulation. This description is to our knowledge the first time domain model of semiconductor media that does not rely upon the integration of semiconductor Bloch equations [4]. We use this tool to study the dynamics and the mode-locking properties of semiconductor Fabry-Pérot lasers when a saturable absorber is included within the cavity. We present a detailed study of the influence of several key parameters that affect the Mode-Locking regime by performing numerical bifurcation diagrams [5] as well as presenting some physical arguments. A vast ensemble of interesting features are reproduced with our approach. We identify the quantum Stark induced bandgap detuning between the gain and the saturable absorber sections as well as thermal detuning to be some key features governing the onset of mode-locking and of self-pulsation. The sharpness of the saturable absorber band-edge, i.e. the transition from transparent to absorptive behavior, is found to induce large wavelength jumps when the bias current is varied. We compare our predictions with the dynamics of AlGaInAs 1.55-µm strained quantum well laser [6].

© 2011 Optical Society of America