Polymer whispering gallery mode sensor for simultaneous measurements of temperature and refractive index

This work presents a Polymethyl Methacrylate (PMMA) whispering gallery mode (WGM) resonator for simultaneous measurements of refractive index and temperature. A single PMMA resonator coupled with a silica waveguide was used to build the sensor and offered multimodal WGM resonance. The coupling gaps and coupling states for the resonator’s modes, along with their minimum transmission/extinction ratios (ER), were investigated. Heatmap barcodes combined with cross-correlation analysis provided insights into the sensor’s performance for single measurands. Lastly, the sensor was analyzed as a dual-analyte sensor. The refractive index sensitivity reached 86 nm/RIU and 60 nm/RIU for the two modes. The temperature responses were 0.131 nm/^∘C and 0.122 nm/^∘C. The characteristic matrix demonstrates the sensor’s potential for simultaneous temperature and refractive index sensing.