Externally pumped high repetition rate femtosecond infrared optical parametric oscillator

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Abstract
The first externally pumped high repetition rate optical parametric oscillator (OPO) 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 μm 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 μm (with KTP) using multiple mirror sets should be possible. This range includes the technologically important regime from 1.0–1.6 μm.