Controlled shaping of ultrafast electric field transients in the mid-infrared spectral range

We experimentally demonstrate amplitude and phase shaping of femtosecond mi d-infrared pulses in a range centered about 14 mu m. Single pulses with a t ailored optical phase and phase-locked double pulses are generated by phase -matched difference-frequency mixing in a GaSe crystal of near-infrared pul ses shaped with a liquid-crystal modulator. The electric field transients a re directly measured by free-space electro-optic sampling, yielding pulse d urations of 200-300 fs. Our data are in good agreement with a model that de scribes phase-matched optical rectification. (C) 2000 Optical Society of Am erica.