Characteristics of infrared pulses generated by optical parametric oscillator from LiNbO3 crystal

Abstract

The optical parametric oscillation (OPO) characteristics of LiNbO3, which is normally pumped by using the 1.064-mum laser output from a nanosecond Nd:YAG laser, were investigated. A 5-cm-long LiNbO3 crystal was cut at theta = 47 degrees, and the OPO cavity was formed by using two plain mirrors. The output coupler reflectivity in the 1.40 - 1.60 mum range was 80.0 %. and the back mirror had a reflectivity of 99.5 % in the 1.45 - 1.55 mum range. At a cavity length of 7 cm and a pump pulse energy of 156 mJ (1.7 times above threshold), the optical parametric oscillator generated nanosecond pulses (signal 1.6 mum and idler 3.18 mum) up to 16 mJ. The change in the output energy was studied as the cavity length was varied from 7 cm to 16 cm at a fixed pump pulse energy of 145 mJ. Mie also measured the OPO output energy as a function of the reflectivity of the output coupler.