Self-Defocusing of Mode-Locked Nd:YAG Laser Radiation in GaAs, CdSe and InP

Abstract
Defocusing in GaAs, CdSe and InP of 25 ps pulse trains from an active-passive mode-locked flashlamp pumped Nd:YAG laser at 1.064 µm is investigated. The distortion of the train envelope and of the spatial beam profile induced by charge carriers created by two-photon absorption are observed at light intensities of 50-100 MW/cm2 for GaAs and CdSe and 25 MW/cm2 for InP. This different behavior is indicative of the different response of InP which is found to be not useful for passive negative feedback of mode-locked Nd:YAG lasers.