Analysis of laser pulse chirping in mode-locked vertical cavity surface-emitting lasers

Mode-locked vertical cavity lasers have a large cross-sectional area and consequently a large saturation energy and large peak powers. The authors analyze excess optical bandwidth generation in these lasers and find that self-phase modulation due to optical pumping and gain saturation is the dominant factor in inducing laser pulse chirping. The large magnitude of the chirp makes intracavity prism-pair compensation difficult. Adjustment of the cavity length has a major impact on the pulse chirping, as observed experimentally. Proper adjustment can result in a large linear frequency chirp which can be compensated using external pulse compression techniques.>