Surface plasmon resonance (SPR) infrared sensor based on D-shape photonic crystal fibers with ITO coatings

A novel surface plasmon resonance sensor (SPR) based on D-shaped photonic crystal fiber (PCF) is designed for sensing low refractive indexes, and its performance is investigated numerically by the finite element method (FEM). Indium tin oxide (ITO) is chosen as the plasmonic materials to expand the operating wavelength range of the PCF-SPR sensor to the infrared region. Spectral sensitivities of 2000–15000 nm/RIU for refractive indexes of 1.22-1.33 are validated in the wavelength range of 1200–2250 nm,and the maximum amplitude sensitivity up to 442.47 RIU−1 is obtained at 2,010 nm with a high resolution of 6.67×10−6RIU. Therefore, the sensor can effectively monitor subtle variations of low refractive indexes and, has enormous commercial value for biomedical and organic detection and related applications.