Tunable whispering gallery mode emission from a microdroplet in elastomer.

A fluorescent microdroplet was formed in elastomer to facilitate handling and wavelength tuning. A methanol solution of rhodamine 6G was put into a solidifying polysiloxane resin with a needle. Addition of surfactant was effective to stabilize the droplet. Being excited by a laser pulse (532 nm, > 50 microJ/mm(2), 5 ns), the droplet exhibited a whispering gallery mode emission in the 570-610 nm wavelength range. The resonance peaks shifted as the droplet diameter expanded by elastomer deformation.