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

A Packaged Whispering Gallery Mode Strain Sensor Based on a Polymer-Wire Cylindrical Micro Resonator

“…Broadband light from a super luminescent diode (SLD) was launched into the fabricated tapered single mode silica optical fiber, which was placed in contact with the polymer MR similarly to the setup described in [18], and the resulting WGM spectrum was recorded at the output of the taper using an optical spectrum analyzer (OSA) with a 10 pm spectral resolution. Periodic narrow resonance peaks with a quality factor of circa ~ 10 3 and average free spectral range (FSR) of 2.35 nm are observed in the wavelength range from 1500 to 1520 nm.…”

“…where Peff is the effective strain-optic coefficient [5,18,20]. The total WGM resonance wavelength shift can be expressed as…”

“…The Poisson's ratio and the effective strain-optic coefficient of PMMA are 0.35-0.45 and 0.099 (±0.0009) respectively [5,18,23,25]. Figure 3 shows the Theoretically calculated and experimentally measured wavelength shift as a function of axial strain for a selected WGM dip.…”

“…It should be noted, that fabrication of such a wire is significantly simpler in comparison with the commercial POF drawing process, since the MR does not require formation of the fiber core. Similar to the previous work [18], the WGMs in the MR were evanescently excited using a tapered silica optical fiber. In the following sections of this paper, we present the results of the characterization of the strain sensor performance.…”

“…Recently we reported a study of a strain-induced spectral tunability of WGMs excited in a coating-stripped POF cylindrical MR [18], fabricated from a short section of commercially available POF with the outer diameter of 490 μm. That study demonstrated that such resonators are potentially very suitable as highly sensitive strain sensors due to the good stability and repeatability of their performance and also due to the excellent elastic properties of the polymer materials, leading to a large dynamic range for strain sensing.…”