Dual-Modal Ionic Polymer Optical Waveguide Grating Sensor for Temperature and Humidity Detection

In this work, a long-period grating (LPG) sensor for dual-modal detection applications using a metal-printing poly(ionic liquid)s (PILs) waveguide is proposed. High-sensitivity temperature and humidity monitoring based on free ionic dynamic mechanism are achieved by an optical-sensing module. The ionic thermal-optic (ITO) and ionic humid-optic (IHO) coefficients of featured PILs waveguide film are obtained as -9.3 × 10⁻⁴/K and -3.1 × 10⁻⁴/% RH, respectively. Both the top humidity sensing and bottom temperature sensing characteristics of the LPG sensor are realized, with a sensitivity of 650 nm/K and resolution of 0.01 K for temperature detection and a sensitivity of 1.05 nm/% RH and resolution of 1% RH for humidity detection, respectively. This optical sensing technique through photonic integrated circuits provides a potential prospect for on-chip multimodal parameter detection.