Dye-doped polymer-coated optical fiber optofluidic laser for refractive index sensing

In this work, we reported an organic dye-doped polymer-coated optical fiber optofluidic laser (FOFL) that supports whispering gallery mode (WGM) laser emission. The dye-doped polymer was coated on the outer surface of single-mode fibers (SMFs) using a simple method to fabricate a uniform and consistent solid gain film. By using coated fibers as optical microcavities for lasers, a low lasing threshold of about 0.65 μJ/mm² was demonstrated. The stability of laser peak wavelengths under different conditions was studied, proving a certain anti-interference ability of the polymer coating. Based on the strong liquid-light interactions brought by the gain film, the application of the polymer-coated fiber laser in refractive index sensing was demonstrated by measuring shifts in laser peak wavelengths, with an obtained sensitivity of about 597.19 nm/refractive index unit (RIU). The presented FOFL design method is expected to be further developed and applied to the designs for FOFL biochemical sensors based on resonance wavelength shifts.