Tunable,narrow-band picosecond radiation in the mid-infrared by difference frequency mixing in GaSe and CdSe

We report on the generation of tunable, narrow-band picosecond laser pulses in the mid-IR at 1 kHz repetition rate. An optical parametric oscillator (OPO) seeded optical parametric amplifier (OPA) delivers signal and idler pulses with energies of several hundred microjoule tunable between 1.56 and 3.24 m. Difference frequency mixing of the OPA signal and idler waves permits the generation of mid-IR radiation between 3 and 24 m. The laser system therefore permits full coverage of the wavelength range between 1.6 and 24 m. Conversion efficiencies greater than 50% and pulse energies up to 40 J are obtained with GaSe. PACS 42.65.Re; 42.65.Yj; 42.72.Ai