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 mum. Difference frequency mixing of the OPA signal and idler waves permits the generation of mid-IR radiation between 3 and 24 mum. The laser system therefore permits full coverage of the wavelength range between 1.6 and 24 mum. Conversion efficiencies greater than 50% and pulse energies up to 40 muJ are obtained with GaSe.