Photonic fibre crystal sensor with a D-shape based on surface plasma resonance containing microfluidic channels for detection of a wide range of refractive indexes

A gold-coated D-shape photonic crystal fibre sensor based on surface plasmon resonance (PCF-SPR) is designed with microfluidic channels and numerically investigated for detection of a wide range of refractive indexes. The D-type structure and microfluidic channels improve the performance of the sensor by reducing the distance between the core and channel and increasing the coupling strength of the fundamental and plasmonic modes. By optimizing the structural parameters, the PCF-SPR sensor can realize a broad range of detection for low RIs changing from 1.23 to 1.36. The maximum spectral sensitivity of 18,000 nm/RIU and optimal resolution of 5.56 × 10⁻⁶ RIU are observed for RIs between 1.35 and 1.36. The sensor is capable of detecting analytes with RIs below 1.36 and has great potential in medical diagnosis, drug development, food safety, and water testing.