Suppression of self-induced thermal lensing in stimulated Raman scattering of liquids

Abstract

Stimulated Raman scattering (SRS), due to the interaction of intense laser beams with Raman active media, provides an effective operational mode for frequency conversion, downgraded (primarily in liquids) by self-induced thermal lensing (TL). Here, a unique setup, including a pump laser beam [green (532 nm), 10 Hz, 5 ns] passing through a rotating cell, filled with a saturated aqueous solution of sodium nitrate ( N a N O 3 ) was tested, for conversion to a yellow (564 nm) beam. This distinct geometry allowed each pump pulse to pass through a “fresh” solution, practically eliminating TL. A sharp enhancement in SRS generation ( ∼ 20 % ) and observation of unexpanded beams’ cross sections at the cell exit verified TL removal. The results and the obtained physical insight from the N a N O 3 model system point to the promise of this approach for suppression of impeding TL in frequency conversion by SRS in liquids.