Different temporal behavior for the forward- and backward-circulating radiation within a microdroplet

Spatially resolved nonlinear scattering of a train of picosecond pulses from ethanol microdroplets is investigated. Different time behavior is observed for light with the same and the opposite sense of circulation as the input-coupled light. The forward-circulating light exhibits a smooth, delayed pulse-to-pulse growth, attributed to increased input coupling with time induced by the laser pulses. The backward-circulating light has an irregular time behavior, attributed to near-backward stimulated Brillouin scattering. Increased scattering as a result of CO(2) (compared with He) dissolved gas is demonstrated by an intensity decrease of the spatially precessed radiation on a cavity resonance.