Travelling-wave 1.57-μm optical parametric oscillator driven by a pulsed multimode Nd<sup>3+</sup>:YAG laser
<i>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 Nd</i><sup><i> 3+</i></sup><i>:YAG laser. KTP crystals were used as the OPO nonlinear medium.</i><sup><i> </i></sup><i>At pump energies up to</i><sup><i> </i></sup><i>100 mJ, decreasing the diameter d of the Nd</i><sup><i> 3+</i></sup><i>: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 the KTP crystals total length of 40 mm, the efficiency of the pump conversion to the signal wave pulse reaches 36.5 %. Based on the travelling-wave OPO, a compact, highly effective, eye-safe laser source radiating pulses of up to 35 mJ in energy, 11 ns 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.</i>