A novel ultra-low refractive index photonic crystal fiber sensor based on surface plasmon resonance

Abstract

Since many biopharmaceuticals have low refractive indexes, the demand for corresponding low refractive index photonic crystal fiber surface plasmon resonance (PCF-SPR) sensors increasing rapidly. In this paper, a novel ultra-low refractive indexes PCF sensor based on SPR is proposed. The sensor structure is simple photonic crystal fiber without grinding. The gold pillars are filled in the y-direction pores. The effect of gold pillars of different shapes, positions and sizes on sensitivity is discussed. The effect of two pores size and pitch are also investigated. The sensitivity increases with the dimension of two pores. However, the sensitivity increases first and then decreases with cycle. As a result, the sensor can monitor the analyte refractive index in 1.21–1.49. The maximum x-polarization sensitivity is 5200 nm/RIU, and the maximum y-polarization sensitivity is 4700 nm/RIU in near-infrared wavelength region. Moreover, the corresponding y-polarization and x-polarization linear fits are 0.9999 and 0.9998, respectively. The proposed ultra-low RI PCF-SPR sensor also works well with wide range refractive indexes.