Dependence of Lasing Modes of Microdroplets on Dye Concentration

We have investigated the dependence of lasing modes of dye-doped microdroplets on dye concentrations. Single droplets were confined in an ion trap and irradiated by a pulsed green laser. Polarization characteristics of both emission spectra and microscopic images were obtained for various dye concentrations. As the concentration decreases, the laser lines shift toward shorter wavelength and the structures of the spectra become more complicated while microscopic spatial images changed drastically. Polarization analyses have revealed that, at the most dilute concentration, only lasing with polarization perpendicular to the radial direction occurs in a droplet.