D-Shaped Photonic Crystal Fiber Plasmonic Sensor Based on Au-Ta₂O₅ Composite Micro-grating

A novel D-type photonic crystal fiber optical plasma sensor (PCF-SPR) based on a composite micro-grating of Au and tantalum pentoxide (Ta₂O₅) is proposed. The simulation and corresponding numerical characterization were performed using COMSOL Multiphysic software. In order to obtain a simple and practically feasible structure, the Au plasma material and the sensing medium were placed outside the optical fiber. A thin layer of Ta₂O₅ is used as a coating to protect the gold layer. This composite micro-grating PCF sensor has a maximum sensitivity of 25,000 nm/RIU and sensor unit with a detection resolution of 4.0 × 10⁻⁶/RIU in the near infrared in the refractive index range of 1.34 ~ 1.41. Dependences of loss spectrum on the PCF parameters (air hole diameter and lattice constant) and the grating structure (grating thickness and width) are systematically analyzed. This sensor with grating structure is a more sensitive sensor for broad IR detection, suitable for biosensors, chemical detection, and food safety.