Strain-induced spectral tuning of the whispering gallery modes in a cylindrical micro-resonator formed by a polymer optical fiber

Abstract

A mechanical strain assisted technique for spectral tuning of whispering gallery modes (WGM) in a cylindrical micro-resonator formed by a polymer optical fiber (POF) is investigated. WGMs in the POF-based micro-cylinder are excited by evanescent light coupling using a tapered single mode silica fiber. WGMs observed in the transmission spectrum of the silica fiber taper have a high extinction ratio of up to 19 dB and a quality factor (Q-factor) of up to 2.64×104. The application of tensile axial strain (μϵ) in the range from 0 to 1746 μϵ (0.17%) to the POF micro-resonator results in a linear shift of the WGM spectrum with a sensitivity of 0.66 pm/μϵ. Under the influence of the applied strain, the WGMs undergo a blue shift and return to their initial spectral positions after the strain is decreased. The proposed strain tunable POF micro-resonator has potential applications in fiber optic sensing and tunable micro lasers.