CO2 Laser Tapering of Intrinsic Fabry-Perot Interferometers for Sensing

We present a highly reproducible method of fabricating a tapered intrinsic Fabry-Perot interferometer (IFPI) device with 5~6-μm diameter at the taper waist. A femtosecond laser was applied to inscribe an IFPI with 3-cm cavity length in a single-mode fiber. A CO 2 laser heated tapering process enabled by digitally controlled mirrors and a precision motorized fiber feed system was used to create a stable heating zone with the desired temperature profile for tapering the fiber IFPI cavity. The well-engineered tapering process produced tapered IFPI devices with insertion loss less than 0.3-dB at 1550-nm. A strong evanescent field exposed by the taper section was explored for refractive index sensing. Using swept optical frequency domination reflectometry, the tapered IFPI fiber sensor achieved a minimal refractive index sensing resolution 2×10 -5 . This paper demonstrates an integrated laser fabrication technique to produce tapered fiber optic devices for sensing applications.