Polymer-Coated Hollow Fiber Optofluidic Laser for Refractive Index Sensing

Optofluidic laser is an emerging method for biochemical sensing. The topic on, which kind of structure is the best to integrate the laser resonator and microfluidic channel, is worth to be explored. Here, we report a hollow optical fiber optofluidic laser based on a dye-doped polymer film. This fiber microstructure is a promising candidate that serves both as a laser microresonator and a compact microfluidic channel. The refractive index of the polymer film is higher than silica so that the whispering gallery mode can be supported. The coating process is explored in detail. The laser spectra and threshold properties of the HOF microlaser are investigated. The dye-doped polymer film can be controlled to be as thin as 1.6 μm and a threshold of below 1 μJ/mm 2 can be reached. Thanks to the strong light-liquid interaction enabled by the polymer coating on the inner interface of HOF, sensitive refractive index detection is demonstrated by monitoring the laser wavelength shift, which has the potential for wavelength division multiplexing. This laser sensor is promising for label-free biochemical detection.