A surface plasmon resonance sensor based on concave-shaped photonic crystal fiber for low refractive index detection

A concave-shaped photonic crystal fiber (PCF) combined with square-channel using indium tin oxide (ITO) for surface plasmon resonance (SPR) sensing is proposed. By means of finite element method (FEM) to multiple parameter optimization of structure, the operation wavelength spans from 1270 nm to 1692 nm covering low-loss communication band when a dynamic refractive index (RI) in a range of 1.19 to 1.29, and meanwhile the sensor displays the maximum wavelength sensitivity of 1700-10700 nm/RIU. This is so far the minimum RI detection sensor in the known reported D-shaped PCF-SPR sensors. It reveals the remarkable ability of our sensor to detect the 10−6 scaled smallest RI changes in solutions of medical oxygen, liquid CO2, and fluorine-containing organics, which extremely expands the application of existing PCF-SPR sensors for medical testing, unknown biomolecules and organic chemistry detections.