Design and Theoretical Analysis of High-Sensitive Surface Plasmon Resonance Sensor Based on Au/Ti 3C2Tx-MXene Hybrid Layered D-Shaped Photonic Crystal Fiber

To achieve high-sensitive refractive index (RI) sensing, an Au/Ti 3C2Tx-MXene hybrid layered D-shaped photonic crystal fiber (PCF) based on the surface plasmon resonance (SPR) sensor is proposed theoretically. The cladding of the D-shaped PCF has a hexagonal air-hole arrangement. In addition, the two air holes nearest to the metal layer in the first layer of cladding are reduced to enhance the plasma wave and provide an efficient leakage channel. The two air holes second nearest to the metal layer in the same layer are enlarged to limit the light scattering and guide more energy coupled with the surface plasmon polariton (SPP) mode. A thin layer of the Ti 3C2Tx-MXene and Au film is applied on the surface of the D-shaped PCF to produce plasmon resonances across a wide range of wavelengths. By using the finite-element method, the optical properties of the proposed PCF-SPR sensor are investigated. The results of the numerical analysis show that this sensor has a significant SPR effect, and the resonance loss peaks can be formed at different positions in the wavelength range of 800-2020 nm. The average RI sensitivity reaches 48120 nm/refractive index unit (RIU), and the maximum sensitivity is up to 64600 nm/RIU in the RI range of 1.390-1.415. The RI sensitivity of the Au/Ti 3C2Tx-MXene layered sensor is 2.36 times higher than the sensor with only the Au layer. The proposed structure has unique sensing properties, which can be effectively applied in bio-sensing fields.