Six-Fold D-shaped Surface Plasmon Resonance based Photonic Crystal Fibre Sensor

Abstract

In this work, we design a 6-fold D-shaped photonic crystal fibre based surface plasmon resonance sensor in detail. The sensing performance of a standard 6-fold hexagonal Dshaped PCF-SPR sensor on a large analyte refractive index range from 1.33 to 1.48 was numerically investigated. The numerical results obtained from the finite element method simulations reveal the coupling relations between fundamental core mode and three surface plasmonic modes which have different electric filed distributions for analytes with different refractive index (RI). Two different types of SPRs, namely, `dielectric like' resonance with low-loss peak and `plasmon like' resonance with highloss peak, are also found through a critical analysis on the electric field distribution evolutions of the fibre modes. In order to reduce the negative influence from the subpeak of the secondary SPR on the sensor's dynamic sensing range (DSR), we found that
by adjusting the liquid analyte layer/analyte binding layer thickness from thick layer (1500 nm) to thin layer (500 nm), the DSR can be extended by a ratio of 44.4% from 1.33-1.41 to 1.33-1.45 at the cost of a reduced maximum sensitivity from 7900 nm/RIU to 5300 nm/RIU. Owning to the simple structure design of the proposed sensor, we envisage that this highly sensitive D-shaped PCF-SPR sensor could be developed as a versatile and competitive instrument with a large and flexible refractive index detection range.