Raman lasing near 630 nm from stationary glycerol-water microdroplets on a superhydrophobic surface.

Abstract

We demonstrate, for the first time to our knowledge, Raman lasing from stationary microdroplets on a superhydrophobic surface. In the experiments, glycerol–water microdroplets with radii in the $11–15\mu \mathrm{m}$ range were pumped at $532\mathrm{nm}$ with a pulsed, frequency-doubled Nd:YAG laser. Two distinct operation regimes of the microdroplets were observed: cavity-enhanced Raman scattering and Raman lasing. In the latter case, the Raman lasing signal was higher than the background by more than $30\mathrm{dB}$. Investigation of the Raman spectra of various glycerol–water mixtures indicates that lasing occurs within the glycerol Raman band. Raman lasing was not sustained; rather, oscillation would occur in temporally separated bursts. Increasing the rate of convective cooling by nitrogen purging improved the lasing performance and reduced the average interburst separation from $2.3\text{to}0.4\mathrm{s}$.