Long-wave infrared picosecond parametric amplifier based on Raman shifter technology.

A new method for a long-wave infrared (LWIR), picosecond difference frequency generation (DFG) source using one near-infrared laser and a Raman shifter is experimentally tested and characterized. The signal seed for DFG is a Stokes pulse generated via transient stimulated Raman scattering in a nonlinear medium with a Raman frequency in the 2-20 µm range. A study of the dynamics of the transient Raman regime in liquid C6D6 has shown that the efficiency of Stokes production can be increased and the central wavelength can be controlled by chirping the pump pulse in order to compensate for chirping caused by self-phase modulation. High energy, ≥3 µJ, picosecond pulses at 10.6 µm have been generated in a GaSe crystal pumped by 1 mJ pulses of 1060 nm light from a Nd:glass laser.