Abstract

The availability of high-quality nonlinear crystals, such as KTP, and high-power, femtosecond Ti:sapphire lasers has led to the recent demonstration of broadly tunable femtosecond KTP-based optical parametric oscillators (OPOs).^1-3 While there is intense interest in extending the wavelength range of these systems toward 4 μm, reported results have focused on operation at wavelengths below 3 μm, although an RTA OPO producing pulses at wavelengths as long as 3.65 μm has recently been described.⁴ The long-wavelength operation of noncritically-phase-matched OPOs is limited by the tuning range of the Ti:sapphire pump laser.³ On the other hand, Poynting-vector walk-off severely limits the effective nonlinear interaction length in critically-phase-matched configurations.^1,2

© 1995 Optical Society of America