Instabilities Of Actively Mode-Locked Homogeneously Broadened Lasers Induced By Self-Phase Modulation

Phase-locking of a multimode laser results in the emission of a train of short pulses of constant shape1. This can be achieved by modulating the cavity losses at a frequency matched to the transit time in the resonator. The short pulse circulating in a pulsed laser can be compressed2 by inserting a Kerr medium in the laser cavity, provided self-phase modulation in the Kerr medium is properly adjusted to the dispersion of the gain medium. Self-phase modulation is also known1 to degrade the short pulse shape in several mode-locked solid state lasers.