Cavity Dumping by the Second Harmonic Generation in the Mode-Locked Nd:YAG Laser

A method of cavity dumping by the second harmonic generation that allows one to obtain short and intensive pulses of laser radiation in the visible band is considered. It is based on intracavity second harmonic generation in lasers with highly-reflective mirrors for the fundamental frequency radiation. The second harmonic generation is obtained with the type II crystal and is controlled with the use of a polarizer and a voltage-activated electrooptic crystal inside the cavity. The method enables one to retain the laser beam quality and propagation direction after transformation into the second harmonic. The method may be implemented in solid-state laser systems operating in different modes: mode-locking, Q-switching, and CW. Most effective second harmonic generation is realized in the mode-locked lasers with ps-duration output pulses and peak intensity up to GW/cm2. We propose a theoretical model and analysis of the cavity dumping by the second harmonic generation in the mode-locked solid-state lasers that is based on the Herman A. Haus approach. The dynamics of the pulse formation in the mode-locked regime is investigated; the parameters of the output second harmonic pulses and their dependence on the main system characteristics are determined. It is shown that the output pulse peak intensity, length, and energy per unit area depend on the pump power and loss coefficient in the cavity: to obtain pulses with higher intensity, energy and smaller length, the pump power should be increased and losses decreased to the minimal value possible. One can obtain the output pulses with the energies per unit area coming to several mJ/cm2. The output pulse parameters may also depend on the dumping period. The cavity dumping repetition rate may be as high as MHz