Nanosecond Eye-Safe Laser Generation by KTP- Basedpptical Parametric Oscillator

Abstract

In this work, an eye-safe laser at 1.57 µm wavelength was generated using an extra-cavity type and singly resonant optical parametric oscillator with a return pump beam configuration. It is based on a nonlinear optical crystal, KTP, which is oriented in a non-critical phase matching. Optical parametric oscillator (OPO) was pumped by a Q-switched Nd:YAG laser at 1.064 µm of 40mJ output energy and 30 ns pulse duration. The KTP- based OPO crystal was designed and constructed with a cavity length of 3.8 cm for maximum output energy. Laser pulses at 1.57 μm were obtained with output energies of 1.7 to 12 mJ for pump energies of 6 to 32 mJ. The signal-to-pump energy conversion efficiency up to 37% was achieved from the OPO when the Q-switched Nd:YAG laser is higher than 1 mJ. The overall (signal and idler) conversion efficiency reached 55%.