Highly transient stimulated Raman scattering on high- and low-frequency phonon resonances of a Sr$_{0.9}$Ba$_{0.1}$MoO$_4$ crystal

An investigation of stimulated Raman scattering (SRS) in a crystal of a Sr$_{0.9}$Ba$_{0.1}$MoO$_4$ cationic solid solution under subpicosecond laser pumping with pulse energy of 20 $\mu$J and duration 0.25–6 ps with a controllable chirp is presented. Highly transient SRS with combined (high- and low-frequency) shifts and a small wavelength spacing not only in Stokes, but also anti-Stokes spectral region is observed due to increasing the integral scattering cross section for the secondary low-frequency Raman mode than for the primary high-frequency Raman mode in comparison with an initial SrMoO$_4$ crystal. Under optimum conditions, the first-order Stokes output pulse energy has reached 2.1 $\mu$J и 2.2 $\mu$J with a supercontinuum part of 9% и 30% for high- and low-frequency shifts respectively. Analysis of spectral and temporal structure of output SRS radiation showed stronger influence of competitive nonlinear phenomena of self- and cross-phase modulation on SRS with the low-frequency shift. With negative chirping of the pump pulse, a sharp compression of the pulse of the first-order Stokes component with a low-frequency shift (up to 2.77 times) occurred with an abnormal shift of its spectral line to the short-wave region in comparison with the first Stokes component with the high-frequency shift.