Broadband phase-matched difference frequency mixing of femtosecond pulses in GaSe: Experiment and theory

Phase-matched difference frequency mixing within the broad spectrum of sing le 13 fs pulses from a cavity-dumped, mode-locked Ti:sapphire laser in a Ga Se crystal allows the generation of femtosecond mid-infrared pulses, contin uously tunable in the wavelength range from 7 to 20 mu m. Pulse durations d own to 95 fs at 9.3 mu m are directly measured. Model calculations includin g the full dispersion of GaSe show that the chirp of the pump pulses allows to change both the pulse duration and conversion efficiency obtained in th e nonlinear process, in agreement with the experiment. (C) 1999 American In stitute of Physics. [S0003-6951(99)02334-7].