Raman random lasing — Extremely high conversion efficiency and temperature dependence

Stimulated Raman scattering (SRS) in barium nitrate powder was studied in two temporal modes: excitation by laser pulses of 11 ns and 30 ps from the room temperature to the temperature of liquid nitrogen. For the first time, an increase in the efficiency of SRS conversion by two orders of magnitude was observed when the sample temperature was lowered from room temperature to the temperature of liquid nitrogen. The maximum achieved value of the conversion efficiency was 30 percent. Temporal characteristics of all the SRS components registered in transient mode were measured. The detected effect of the pump energy influence on the delay time of the first Stokes component can be used for measuring the nonlinear parameters of the medium. •SRS conversion efficiency increases at low temperature in random raman media.•SRS energy threshold in transient mode is much lower than in steady-state mode.•The narrowing of the Raman linewidth at temperature of liquid nitrogen was observed.•The pump energy affects the delay time of the first Stokes component.