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Phase-matched second-harmonic generation is obtained in various LiInS(2) crystals by use of the tunable picosecond output of the free-electron laser for infrared experiments (FELIX) as the pump source in the mid-IR range from 2.75 to 6.0 microm. Deviations from the phase-matching curve calculated from Boyd's refractive-index data are observed. Furthermore, the optical damage threshold of the crystals has been measured to be 1.1. J/cm(2)(>6 GW/cm(2)) at the 5-microm wavelength. LiInS(2) holds great promise for parametric interaction in the 1-13-microm range.

Subpicosecond synchronization between a mirror-dispersion-controlled 10-fs Ti:sapphire laser and the Free-Electron Laser for Infrared Experiments has been achieved. The measured intensity cross correlation between the two lasers is consistent with a jitter of only 400 fs rms. The wide and continuous tunability of the free-electron laser (FEL; 4.2-300mum) combined with ultrashort pulse duration of six optical cycles and high pulse energy of several tens of microjoules makes a series of two-color experiments possible in a previously inaccessible wavelength range. We demonstrate these capabilities by performing a two-color pump-probe experiment to study carrier cooling in GaAs. A FEL tuned from 8 to 17mum is used as the pump, and a synchronized Ti:sapphire laser pulse serves as the probe.