Periodically poled lithium niobate optical parametric amplifiers pumped by high-power passively Q-switched microchip lasers

High-power passively $Q$-switched microchip lasers produce 157-$\mathit{\mu }\mathrm{J}$ pulses of 1-ns duration in a single-frequency, diffraction-limited output beam. The unfocused 1.064-$\mathit{\mu }\mathrm{m}$ output of these devices has been used to drive periodically poled lithium niobate optical parametric amplifiers at wavelengths between 1.4 and 4.3 $\mathit{\mu }\mathrm{m}$. With a peak conversion efficiency of nearly 100%, these devices generate 100-kW, subnanosecond pulses in the mid IR, with a beam quality that is better than two times diffraction limited.