EXTERNALLY PUMPED HIGH REPETITION RATE FEMTOSECOND INFRARED OPTICAL PARAMETRIC OSCILLATOR

The first externally pumped optical parametric oscillator which produces tunable femtosecond pulses in the near-infrared is demonstrated. The singly resonant oscillator with a KTiOPO4 (KTP) nonlinear crystal is synchronously pumped by 150-fs pulses at 645 nm from a mode-locked dye laser. With a pump power of 280 mW, stable 220-fs pulses at a 76-MHz repetition rate, tunable from 1.20 to 1.34-mu-m with a single set of mirrors, are achieved. The internal power conversion efficiency is 13% and the average infrared power is as large as 30 mW, for the signal beam only. Femtosecond pulses tunable over the wavelength range from 0.9-4.5-mu-m (with KTP) using multiple mirror sets should be possible. This range includes the technologically important regime from 1.0-1.6-mu-m.