Continuously tunable microdroplet-laser in a microfluidic channel

This paper describes the generation and optical characterization of a series of dye-doped droplet-based optical microcavities with continuously decreasing radius in a microfluidic channel. A flow-focusing nozzle generated the droplets (similar to 21 mu m in radius) using benzyl alcohol as the disperse phase and water as the continuous phase. As these drops moved down the channel, they dissolved, and their size decreased. The emission characteristics from the drops could be matched to the whispering gallery modes from spherical micro-cavities. The wavelength of emission from the drops changed from 700 to 620 nm as the radius of the drops decreased from 21 mu m to 7 mu m. This range of tunability in wavelengths was larger than that reported in previous work on droplet-based cavities. (C)2011 Optical Society of America