Ultra-Low Loss D-Type Photonic Crystal Fiber Sensor Based on Surface Plasmon Resonance

A D-type photonic crystal fiber (PCF) sensor with ultra-low loss is presented in this paper. The sensor is capable of detecting analytes in the refractive index (RI) range of 1.36 to 1.42. When the RI of the analyte is 1.36, the maximum loss of the sensor in the x-polarized direction is only 23.25 dB/m. A maximum wavelength sensitivity of 8000 nm/RIU is obtained as the analyte has a RI of 1.42, and the sensor has an average wavelength sensitivity of 4678 nm/RIU in the x-polarization direction. The design of the sensor is implemented by coating the side-polished surface of the PCF with a gold film. For the high-sensitivity sensor, the deposition of gold can provide excellent optical performance while maintaining an ultra-low loss. In general, the designed D-type PCF sensor based on side-polished flat gold layer has great potential in various sensing applications due to its ultra-low loss, high sensitivity, and stable properties.