We present a highly efficient ring-cavity all-solid-state BaWO Raman laser generating at both the long-shift (ν=925  cm) and short-shift (ν=332  cm) Raman lines under external picosecond synchronous pumping at the wavelength of 1063 nm. Very high slope efficiencies and output pulse energies of 68.8% and 103 nJ at the ν-shifted Stokes wavelength of 1179 nm, and 38.6% and 53 nJ at the (ν+ν)-shifted Stokes wavelength of 1227 nm have been achieved. Self-mode locking of the (ν+ν)-shifted Stokes field under intracavity pumping by the ν-shifted Stokes field allowed to realize 12-fold shortening of the 1227 nm radiation pulse down to 3 ps close to the shorter dephasing time of the ν Raman line at the output pulse peak power 1.5 times higher than the pump peak power.

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Comparative investigation of characteristics of spontaneous and stimulated Raman scattering (SRS) in different alkali-earth tungstate and molybdate crystals at both high and low frequency anionic group vibrations is presented. It has been found that, among these crystals, the SrMoO4 and SrWO4 crystals are the most perspective for SRS generation on both stretching and bending modes of internal anionic group vibrations with the strongest SRS pulse shortening under synchronous laser pumping because of not only highly intense stretching mode Raman line for efficient primary extra cavity long-shifted SRS conversion but also the widest bending mode Raman line for the strongest SRS pulse shortening down to the inverse width of the widest Raman line (~1 ps) at secondary intracavity short-shifted SRS conversion. The strongest 26-fold pump pulse shortening down to 1.4 ps at the Stokes component with the combined Raman shift in the synchronously pumped extra cavity SrMoO4 and SrWO4 Raman lasers has been demonstrated. It was found that synchronously pumped cascade SRS with combined Raman shift is more efficient in the SrWO4 crystal because the bending mode Raman line is more intense relative to the stretching mode Raman line than that in SrMoO4.

For the first time to our knowledge, the operation of a synchronously pumped ultrafast Raman laser that uses a PbMoO4 crystal as the active medium has been demonstrated. We achieved efficient Raman conversion in PbMoO4 from pumping 1063 nm into 1171 and 1217 nm, respectively, at single and combined frequency shifts on stretching and bending Raman modes. The output pulse energy (up to 160 nJ) and peak power (up to 11 kW) of the output picosecond radiation is the highest among all-solid-state synchronously pumped Raman lasers published to date. The strongest pulse shortening at 1217 nm down to 1.4 ps was obtained that is close to the bending mode dephasing time.

The first femtosecond crystalline Raman laser pumped by a picosecond laser is demonstrated. The method consisted of a synchronously pumped cascade SRS process. This process is started with extracavity Raman conversion from pump radiation into the long-shifted Stokes component and continues with secondary intracavity Raman conversion from the long-shifted Stokes component into the Stokes component with combined long and short Raman shift. This secondary conversion shows strong pulse shortening down to the inverse width of the widest short-shift Raman line. We report characteristics of the all-solid-state extracavity Raman laser based on the 16 mm long a-cut GdVO 4 crystal under synchronous pumping by the 1063 nm 36 picosecond 150 MHz Nd:GdVO 4 laser. Cascade two-wavelength Raman generation in the external high-Q ring cavity has been obtained not only at the usual wavelength of 1174 nm corresponding to the long-shifted first Stokes component, but also at the unusual wavelength of 1228 nm having the combined long and short Raman shift. The individual pulse energy of the 1228 nm radiation was up to 10 nJ and slope efficiency of 5%. Significant shortening of the 36 ps pump pulse down to 860 fs at 1228 nm has been demonstrated without using any compressor.