Efficient nanosecond optical parametric oscillators based on periodically poled KTP emitting in the 1.8-2.5-μm spectral region

The use of periodically poled KTiOPO4 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-mu m spectral region was achieved when the crystal temperature was tuned from 10 to 100 degrees 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 hacking or laser damage was observed, even for pump intensities of 450 MW/cm(2). (C) 1999 Optical Society of America.