Stimulated Raman scattering of 0.3-ps 515 nm laser pulses in Ca$_3$(VO$_4$)$_2$ and Ca$_{0.27}$Sr$_{0.3}$(VO$_4$)$_2$

The prospects of SRS-active calcium/strontium orthovanadate crystals, (Ca$_3$(VO$_4$)$_2$ and Ca$_{0.27}$Sr$_{0.3}$(VO$_4$)$_2$), or spectral conversion of ultrashort visible-range laser pulses evaluated in a single-pass scheme with pump focusing into the samples. For the 3 $\mu$J incident laser pulses of 0.3 ps duration at wavelength of 515 nm the energy conversion efficiency of up to $\sim$3.5% to the Stokes component shifted in frequency by $\sim$850 cm$^{-1}$ obtained in a 1.3 cm long sample of Ca$_{0.27}$Sr$_{0.3}$(VO$_4$)$_2$ crystal. Simultaneously, in the transmitted radiation spectrum the amplitude of Stokes component reached 1/3 of the amplitude at the pump wavelength. Under the same conditions, SRS in a Ca$_3$(VO$_4$)$_2$ crystal was not detected at all. It was shown that the observed differences can be explained by the attenuation of pump pulse due to difference in two-photon absorption in these crystals.