Travelling-wave 1.57-Μm Optical Parametric Oscillator Driven by a Pulsed Multimode Nd 3+ :YAG Laser

The generation properties of an optical parametric oscillator (OPO) with a three-mirror ring resonator have been investigated under conditions of a pulsed pump by multimode radiation from a Nd3+:YAG laser. KTP crystals were used as the OPO nonlinear medium. At pump energies up to 100 mJ, decreasing the diameter d of the Nd3+:YAG laser beam causes a decrease in OPO radiation divergence and an increase in the generation efficiency at λ = 1.571 µm despite a decrease in the differential efficiency. At d = 2.25 mm and a KTP crystal total length of 40 mm, the efficiency of the pump conversion to the signal-wave pulse reaches 36.5%. Based on the traveling-wave OPO, a compact, highly effective, eye-safe laser source radiating pulses of up to 35 mJ in energy, 11 nsec in duration, and 10 Hz in repetition rate at electrical pump energy of ≤ 8 J is developed. At the 86.5% level of the total pulse energy, the source-beam divergence does not exceed seven diffraction limits.