Pump spectral linewidth influence on stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) and self‐termination behavior of SRS in liquids

Abstract

The threshold, temporal behavior, and conversion efficiency of stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SBS) in three liquids (benzene, hexane, and dimethyl sulfoxide) and two crystals (calcite and barium nitrate) have been investigated under three largely different spectral linewidth conditions. Pumped with 532‐nm and nanosecond duration laser pulses of ≤ 0.01 cm−1 linewidth, only SBS can be generated in all tested liquids with a high nonlinear reflectivity. However when the pump spectral linewidth is ∼0.07 cm−1 or ∼0.8 cm−1, both SBS and SRS can be observed in benzene while only SRS can be generated in dimethyl sulfoxide; in all these cases SRS is the dominant contribution to the stimulated scattering but the efficiency values are drastically decreased due to the self‐termination behavior of SRS in liquids, which arises from the thermal self‐defocusing of both pump beam and SRS beam owing to Stokes‐shift related opto‐heating effect. In contrast, for SRS process in the two crystals, the thermal self‐defocusing influence is negligible benefitting from their much greater thermal conductivity, and a higher conversion efficiency of SRS generation can be retained under all three pump conditions.image

Intramolecular Vibration Energy-Transfer-Driven Cascaded Stimulated Raman Scattering and Four-Wave Mixing in Benzene Series

“…In addition, to examine the temporal behavior of SRS in chlorobenzene, the simultaneous temporal waveforms of the pump laser pulse, transmitted pump pulse, and the forward SRS pulse were measured (Figure S3). The result indicated that the self-terminating behavior of SRS was generated in liquids …”

“…The result indicated that the self-terminating behavior of SRS was generated in liquids. 26 Kerr self-focusing effect is always taking place together with the SRS process. Kerr self-focusing is of major importance for the onset of SRS.…”