Lasing droplets in a microfabricated channel.

Lasing from spherical microdroplets ejected into a liquid medium with a lower refractive index is observed in a microchannel. A microfabricated device that combines droplet production and excitation/detection has been utilized. Droplets of 50 microm diameter containing a fluorescent dye were first detected and then excited through multimode fibers after their production at a T-junction. Images show intense lasing emission around the droplet rim. Spectra from the droplets exhibit morphology-dependent resonances that are redshifted relative to the bulk fluorescence emission from the dyes. The dependence of resonant peak intensities on the pump beam power is nonlinear.