A high-repetition-rate, singly resonant optical parametric oscillator based on KTiOAsO4 and synchronously pumped by a self-mode-locked Ti:sapphire laser is reported. Under the conditions of pump-tuned noncritical type II phase matching, average near-infrared output powers of 403 mW have been generated at a repetition rate of 81 MHz. With the available mirror set, signal tuning over 1.116-1.281 mu m and idler tuning over 2.260-3.160 mu m are demonstrated for a range of pump wavelengths. Without dispersion compensation, signal (idler) pulses with durations of 1.01-1.03 (1.61-2.91) ps have been obtained for 1.2-ps input pump pulses. (C) 1996 Optical Society of America