Generation and field-resolved detection of femtosecond electromagnetic pulses tunable up to 41 THz

Bandwidth-limited infrared pulses as short as 50 fs are generated in thin GaSe crystals by phase-matched optical rectification of 10 fs laser pulses. The central frequency of the transients is continuously tunable over a wide interval extending from 41 THz (lambda=7 mu m) to the far-infrared. The electric field of the THz transients is directly monitored via ultrabroadband free-space electro-optic sampling. A simulation of the spectra based on a plane-wave model shows excellent agreement with the experiment. (C) 2000 American Institute of Physics. [S0003-6951(00)05422-X].