Tunable Picosecond Pulse Generation by Optical Parametric Oscillator

An optical parametric oscillator has been constructed in which a temperature-controlled LiNbO 3 crystal in a resonant cavity is pumped by the second harmonic of a mode-locked glass:Nd laser. It produces broadly tunable (λ: 0.62–3.5 µm), intense (peak power 10 MW), ultrashort pulses (pulse width ∼ 60 ps) with a narrow spectral width (Δλ∼0.1 nm in the red region) and a small beam divergence (Δθ<1 m rad). The tunable range has been extended up to 0.31 µm by efficient frequecy doubling of the signal in an RDP crystal. The usefulness of this coherent light source in the picosecond optical spectroscopy has been demonstrated.