Broad-bandwidth parametric amplification in the visible: femtosecond experiments and simulations

A general geometric condition, involving group velocities, for large bandwidth parametric amplification with all types of phase-matching and in certain wavelength ranges is derived. This condition has been exploited to produce visible widely tunable sub-20-fs pulses from an optical parametric oscillator and an optical parametric amplifier based on /spl beta/-barium borate (BaB/sub 2/O/sub 4/) pumped in the blue. These results are interpreted in terms of a modified soliton model for the optical parametric oscillator (OPO) and detailed numerical simulations for both devices.