Ultrasensitive label-free coupled optofluidic ring laser sensor.

A coupled optofluidic ring laser sensor is fabricated, and its ultrasensitive bulk refractive index and surface mass sensing properties are demonstrated. The sensor consists of a cylindrical ring laser and a thin-walled optofluidic capillary ring resonator. Coupling of the whispering gallery mode in the two resonators generates a largely magnified sensitivity due to the Vernier effect. A sensitivity of 2510 nm/RIU and magnification factor of 355 are achieved experimentally in aqueous solution, which corresponds to a noise equivalent detection limit of 1.6×10(-5) RIU for bulk RI detection. The new sensor configuration provides a convenient way to achieve ultrasensitive biological and chemical sensing.