Formation of 1- to 2-ns high-energy OPO/OPA pulses

Summary form only given. The main goal of the scheme presented is to combine the possibilities of generating short tunable pulses (1-2 ns) within the 1.8 to 2 /spl mu/m range with narrow frequency bandwidth and achievement of high energy (/spl sim/100-150 mJ). To fulfil this task, several stimulated Brillouin scattering (SBS) cells were used to prepare two pulses with different pulse widths. The first pulse of 150 mJ, 25 ns duration was used to excite the OPO. Afterwards, this pulse was converted into two pulses, a long pulse and a short pulse. The long pulse was formed due to reflection from a mirror SBS cell placed near the OPO. It provided simultaneous illumination of the nonlinear crystal inside the OPO cavity via both counter-propagated pumps. Such illumination allowed for the generation of one longitudinal OPO mode and generated a more stable frequency spectrum. The short pulse was formed due to reflection from a mirror SBS cell placed away from the OPO and subsequent compression in another SBS cell. The second pump was used to amplify the signal in the OPA. A 1.5-ns pulse with 800 mJ energy for pumping the OPA was generated by reflecting the pulse from a mirror SBS cell. This mirror cuts the front of the master oscillator pulse, and this is why the subsequent amplification in the laser amplifier leads to pulse compression. Quantum efficiency of the conversion reached 40%. The level of energy achieved together with pulse width provides the highest power of tunable radiation in the mid-IR range. It presents new opportunities for frequency conversion. In particular, 100-MW OPO/OPA pulses can be successfully used for the excitation of SRS in the far IR.