High-sensitive and linear temperature sensor based on liquid-filled photonic crystal fiber

This study introduces a temperature sensor based on solid-core photonic crystal fiber that exhibits insensitivity to polarization. The coupling condition between the core and defect modes is investigated by employing the finite element method. To enhance sensitivity, a thermo-sensitive liquid with a refractive index of 1.65 at 25 °C is injected into the second ring air holes, and a polydimethylsiloxane layer is applied around the filled holes. The impact of the polydimethylsiloxane layer and air hole sizes on the sensing performance is thoroughly analyzed. The proposed sensor’s sensing property is evaluated by varying the temperature from 20 to 80 °C, resulting in an average sensitivity of − 3.166 nm/°C. The correlation coefficient is as high as 0.99992 and demonstrates the high linearity of the designed sensor. The full-width at half-maximum and the figure-of-merit are 11 nm and − 0.287/°C, respectively. Furthermore, a resolution of 0.03191 °C and an accuracy of 0.091 /nm show an excellent performance for the proposed device. The sensor’s desirable features include high sensitivity, linearity, symmetrical structure, and equal sensitivity for both X and Y polarizations, making it suitable for practical applications. Furthermore, by adjusting some geometrical factors such as the lattice pitch, diameter of holes, number of rings, and thickness and concentration of materials, the sensor can be optimized for favorable operating conditions.