A quasi-droplet optofluidic ring resonator laser using a micro-bubble

Optofluidic ring resonator lasers based on micro-bubbles filled with liquid gain medium are demonstrated. Due to the sub-micron wall thickness of the micro-bubble, significant amount of the electric field resides inside the liquid. Consequently, micro-bubbles mimic the droplets in air that have 3-dimensional optical confinement, extremely high Q-factors, and versatility in handling liquids of different refractive index. Furthermore, they enable repetitive interrogation and easy directional laser emission out-coupling without evaporation or size/shape variations. The laser using Rhodamine 6G in methanol is achieved with a threshold of 300 nJ/mm(2) and 5.3 mu J/mm(2) for 1 mM and 10 mu M in concentration, respectively. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3629814]