FEMTOSECOND OPTICAL PARAMETRIC OSCILLATOR BASED ON PERIODICALLY POLEDLITHIUM-NIOBATE

We describe a femtosecond optical parametric oscillator based on perio dically poled lithium niobate and pumped by a self-mode-locked Ti:sapp hire 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 meas ured and, in the absence of optimized output coupling, signal powers o f 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 s ignal. Dispersion compensation produced near-transform-limited signal pulses of duration 140 fs. Observations regarding temperature tuning a nd pump depletion are also presented. (C) 1998 Optical Society of Amer ica.