The use of periodically poled KTiOPO<sub>4</sub> as a gain medium in efficient nanosecond optical parametric oscillators pumped by a flash-lamp-pumped Q-switched Nd:YAG laser is demonstrated. Parametric radiation in the 1.8–2.5-μ m spectral region was achieved when the crystal temperature was tuned from 10 to 100°C. A maximum total output energy of 1.8 mJ was obtained at a pump level of 3.5 mJ. Stable operation was achieved, with conversion efficiencies reaching 50%. No gray tracking or laser damage was observed, even for pump intensities of 450MW/cm<sup>2</sup>.
© 1999 Optical Society of America
J. Hellström, V. Pasiskevicius, F. Laurell, and H. Karlsson, "Efficient nanosecond optical parametric oscillators based on periodically poled KTP emitting in the 1.8–2.5-μm spectral region," Opt. Lett. 24, 1233-1235 (1999)