Generation of subpicosecond infrared pulses tunable between 5.2 mu m and 18 mu m at a repetition rate of 76 MHz

Infrared (IR) pulses are generated via difference frequency mixing of the signal and idler output of an optical parametric oscillator (OPO), pumped by a Ti:sapphire laser at a repetition rate of 76 MHz. AgGaS2 (2 mm thick) and GaSe (1 mm thick) crystals are applied as nonlinear media. GaSe has a larger tuning range and is more efficient in the whole spectral range than AgGaS2. The average IR power reaches up to 2.0 mW at 8.5 mu m, when the GaSe crystal is used, and up to 1.3 mW at the same wavelength when AgGaS2 is applied for the frequency conversion.