Double-D-type high-sensitivity photonic crystal fiber-optic sensor based on water pollution detection

A highly sensitive photonic crystal fiber-optic sensor of the double-D type is proposed in this paper for the sensitive detection of contaminants in water. The sensor is made up of a double-D-type photonic crystal fiber with six large air holes symmetrically distributed in the outer layer and four large air holes in the core. To activate the surface plasmon resonance effect, gold nanofilms are uniformly coated into the U-shaped microchannels located at the top and bottom of the core region. The sensor is capable of detecting minute fluctuations in the refractive index (RI) of water that are induced by pollutants, such as hydrogen peroxide (H 2 O 2 ) and nitric acid (HNO 3 ) at varying concentrations. The finite element method was employed to conduct a modal analysis of the structure to enhance the RI sensitivity by examining the geometric parameters. The simulation results indicate that the sensor operates at a maximum wavelength sensitivity of 11,200 nm/RIU, an optimum resolution of 8.93×10 −6 RIU, and a maximum quality factor of 79.3RIU −1 within the refractive index range of 1.33–1.365. Consequently, the sensor offers a detection method for water pollutants that is highly sensitive.