A Packaged Whispering Gallery Mode Strain Sensor Based on a Polymer-Wire Cylindrical Micro Resonator
We propose a whispering gallery mode (WGM) strain sensor formed by a polymer-wire cylindrical micro resonator for strain measurement applications. WGMs are generated by evanescently coupling light into the polymer-wire resonator from a silica fiber taper fabricated by the micro heater brushing technique. Accurate and repeatable measurements of strains up to one free spectral range shift of the WGMs (corresponding to 0.33% of the polymer-wire elongation, 3250 $\mu\epsilon$) are demonstrated experimentally with the proposed sensor. Practical packaging method for the proposed strain sensor on a glass microscope slide has also been realized making the sensor portable and easy to handle. The robustness of the packaged coupling system is confirmed by vibration tests. The performance of the packaged strain sensor is evaluated and compared with that for an unpackaged sensor.