Submicron accuracy fiber taper profiling using whispering gallery modes in a cylindrical fiber micro-resonator

This paper experimentally demonstrates a method for geometrical profiling of thin microfiber tapers with small waist diameters ranging from 10 to 40 μm with submicron accuracy. The method is based on analysis of whispering gallery mode resonances excited in cylindrical fiber resonators as a result of evanescent coupling of light propagating through the fiber taper under test. Measurement results have been verified by optical and SEM microscopic studies. The proposed method can be applied in the fabrication of fiber micro tapers for accurate control of the taper profile and in sensing of biochemical species on the surface of the microfiber.