Phase-matched difference frequency mixing within the broad spectrum of single 13 fs pulses from a cavity-dumped, mode-locked Ti:sapphire laser in a GaSe crystal allows the generation of femtosecond mid-infrared pulses, continuously tunable in the wavelength range from 7 to 20 μm. Pulse durations down to 95 fs at 9.3 μm are directly measured. Model calculations including 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 the nonlinear process, in agreement with the experiment.
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© 1999 American Institute of Physics.
1999
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