Generation and complete electric-field characterization of intense ultrashort tunable far-infrared laser pulses

Intense rapidly tunable picosecond laser pulses have been generated in the far infrared from 30 to 250 mu m, a range not well covered by other sources. The transform-limited, diffraction-limited pulses have energies of up to 17 mu J, peak powers of more than 1 MW, a length of only 18 optical periods, and focused intensities of 0.1 GW/cm(2). Measurements of both the optical field amplitude and the phase have been performed at 150 mu m with a rapid-scanning cross-correlation technique probing the field-induced birefringence in ZnTe with a 10-fs Ti:sapphire laser. The far-infrared laser opens up the exciting possibility of performing nonlinear experiments in a relatively unexplored spectral range.