Characteristics of lasing spectrum from dye-doped ethanol micro-spherical shell

A monodisperse stream of ethanol solution droplet was produced by a vibrating orifice particle generator. Carbon dioxide was dissolved in ethanol solution containing Rhodamine 6G at high pressure (5 atm). Because the liquid is forced through the orifice at high pressure and immediately exposed to the lower atmospheric pressure (1 atm), the droplet solution is effectively supersaturated with gas and bubbles spontaneously. A Q-switched Nd:YAG laser (532 nm) and a CW-Ar laser (514nm) was used as the pumping source in each. A photo-diode array in the image plane of a spectrometer detects the lasing spectrum of light emitted normal to the stream of ethanol droplets. The signals from PDA were displayed on the oscilloscope. Lasing spectrum in hollow droplets shows modes of single order, but lasing spectrum in homogeneous droplet shows modes of double order.