Stimulated emission and amplification of radiation under conditions of stimulated Raman scattering in crystals

An experimental study was made of the generation of Stokes radiation in focused beams under conditions of stimulated Raman scattering (STRS) in calcite and barium nitrate crystals. A high efficiency (~0.8) of conversion of the pump energy into the Stokes radiation energy was achieved for the opposed STRS and it was found that this was due to four-photon parametric processes. The quality of wavefront reversal of spatially homogeneous and inhomogeneous beams was determined in a wide range of energies and divergences of the pump radiation and also in a wide range of the focal lengths of the lenses employed in the process. Further amplification of radiation was achieved in an STRS amplifier made of barium nitrate and operating in the intensity averaging regime. Under saturation conditions the efficiency of conversion of the pump energy into the Stokes radiation energy was ~0.8 and the small-signal gain was ~ 1.3 × 10³.