Pseudo Whispering Gallery Mode Optofluidic Lasing Based on Air-Clad Optical Fiber

We report a fiber optofluidic laser based on a commercial air-clad optical fiber (ACF). The ACF with air holes surrounding the silica core supports pseudo whispering gallery mode, which can provide optical feedback for lasing. 1 mm Rhodamine 6G in quinoline (n = 1.63) is withdrawn into the ACF using the capillary action. Due to the high refractive index difference between gain medium and silica, about 83% of light intensity is confined within the liquid gain medium, leading to a low threshold of about 1.1 μJ/mm
²
. The lasing mechanism is investigated by both numerical simulation and experimental demonstration. The laser emission was observed with various refractive index in the range between 1.52 and 1.63. The proposed fiber optofluidic laser is promising for biochemical sensing.