Optical Spectroscopy and Microscopy of a Single Dye-Doped Microdroplet Levitated in an Ion Trap

摘要

Single dye-doped glycerol rnicrodroplets levitated in an electro-dynamical trap were irradiated by a cw or a pulsed green laser, and both emission spectra and microscopic images were simultaneously obtained and compared for various pump intensities. Neither the spectra nor the images of strongly excited droplets resembled those of weekly excited ones. From emission spectra, it was found that the levitated microdroplet acts as a high Q resonator and lasing action occurs above a certain threshold. Below the threshold, the image was nearly uniform, reflecting the fluorescence from almost entire region of the droplet. Above the threshold, however, the images exhibited symmetrically arranged bright spots near the surface of the droplet, which suggests that the lasing action occurs in specific surface azimuthal modes in the droplet.