Broadly tunable high repetition rate femtosecond optical parametric oscillator

Abstract

We report a new source of femtosecond light pulses which is broadly tunable in the infrared. A singly resonant optical parametric oscillator based on a thin crystal of KTiOPO₄ is pumped by intracavity femtosecond pulses at 620 nm from a standard colliding‐pulse passively mode‐locked dye laser. Oscillation results in stable, continuous outputs of femtosecond pulses at 10⁸ Hz repetition rate and milliwatt average power levels in both signal and idler beams. Here we demonstrate tuning from 820 to 920 nm and 1.90 to 2.54 μm with a single set of mirrors. With multiple sets of mirrors, continuously tunable outputs from ∼0.72 to ∼4.5 μm should be possible, making this a uniquely versatile femtosecond laser source.