Cavity dumping by the second harmonic generation in the Q-switched Nd : YAG laser

Abstract

This paper presents the cavity dumping method by the second harmonic generation in a neodymium laser operating in the Q-switched mode. Theoretical modeling of the laser generation in dynamics is performed. The main characteristics of the output pulses and their dependence on the pump power and coefficient of losses are calculated. The proposed method can be implemented in the laser with a second harmonic crystal inside the cavity and an electro-optical crystal, which is operated by a step voltage pulse. The switching pulse length is defined by the time needed to achieve the maximum giant pulse intensity in the cavity, and is in the order of 0.1–1.0 ms depending on the pump power. Moreover, the voltage pulse jitter should not exceed several nanoseconds. In such case the second harmonic pulses with nanosecond duration and peak intensity of 10 –100 MW/cm2 are generated at the laser output. The output pulses duration is defined only by the cavity length under the conditions of a small response time of the electro-optical crystal compared to the cavity round-trip time. To achieve the maximal peak intensity, one should decrease the coefficient of inactive losses to the possible minimum and increase the pump power.