  We present the first observation, to our knowledge, of lasing from a
levitated, dye droplet. The levitated droplets are created by computer
controlled pico-liter dispensing into one of the nodes of a standing ultrasonic
wave (100 kHz), where the droplet is trapped. The free hanging droplet forms a
high quality optical resonator. Our 750 nL lasing droplets consist of Rhodamine
6G dissolved in ethylene glycol, at a concentration of 0.02 M. The droplets are
optically pumped at 532 nm light from a pulsed, frequency doubled Nd:YAG laser,
and the dye laser emission is analyzed by a fixed grating spectrometer. With
this setup we have achieved reproducible lasing spectra in the visible
wavelength range from 610 nm to 650 nm. The levitated droplet technique has
previously successfully been applied for a variety of bio-analytical
applications at single cell level. In combination with the lasing droplets, the
capability of this high precision setup has potential applications within
highly sensitive intra-cavity absorbance detection.
