Coupled optofluidic ring laser for ultrahigh-sensitive sensing.

Ultrahigh sensitivity is achieved in a new active sensor structure: coupled optofluidic ring laser. The sensor consists of one ring laser and one optofluidic tube. The emission intensity of the multimode whispering gallery resonance from the coupled ring laser is strongly modulated. By using the optofluidic tube as the sensing element, and monitoring the envelope shift of the modulated lasing spectrum, we achieved a sensitivity of 5930 nm/RIU, which is two orders of magnitude higher than a conventional ring resonator sensor.