Femtosecond optical parametric oscillator based on periodically poled lithium niobate

We describe a femtosecond optical parametric oscillator based on periodically poled lithium niobate and pumped by a self-mode-locked Ti:sapphire laser. Signal and idler outputs almost continuously tunable from 975 nm to 4.55 mu m were generated by a combination of grating tuning and cavity-length tuning, and an explanation of the tuning properties is given in terms of the gain bandwidth. A threshold of 45 mW was measured and, in the absence of optimized output coupling, signal powers of 90 mW and idler powers of 70 mW were obtained, with 140 mW of green light at 540 nm generated by phase-matched frequency doubling of the signal. Dispersion compensation produced near-transform-limited signal pulses of duration 140 fs. Observations regarding temperature tuning and pump depletion are also presented. (C) 1998 Optical Society of America.