Resonance parametric excitation of temperature oscillations in levitating aerosol droplets

The threshold conditions of excitation of temperature oscillations in high-Q water aerosol droplets have been studied under the conditions of slow evaporation. Selection rules have been obtained for interacting modes in a droplet. The threshold intensity of excitation of temperature oscillations has been analyzed in comparison with the threshold intensity of stimulated Brillouin and stimulated Raman scattering in a droplet. It is shown that, in the three-mode regime, the temperature oscillations can be excited at a rather low pumping level (about 10 W/cm²). A method is proposed for the remote measurement of the microphysical parameters of a droplet from the periodic temperature shift of eigenfrequencies of a droplet, the threshold intensity of excitation of temperature oscillations, and the thermal Raman frequency.