Theoretical study of colliding pulse passively mode-locked semiconductor ring lasers with an intracavity Mach–Zehnder modulator

In this paper, we theoretically study the impact of an intracavity filter based on a Mach-Zehnder interferometer (MZI) on the pulses emitted by InGaAsP/InP passively mode-locked quantum well ring lasers. The filter allows to control the net gain curvature in the device, hereby providing for control over the modes that participate in the dynamics. Simulations of a traveling-wave model indicate that the pulsewidth can be controlled and reduced down to 500 fs. We present and verify a simple algorithm, which can be used for calculating the optimum values of the MZI parameters. The optimum parameters are then used in the study of an MZI passive-mode-locked laser under various operating conditions