High-sensitivity refractive index sensor with tunable detection range based on dual-core resonance effect in gold-coated photonic crystal fibers**Project supported by the National Natural Science Foundation of China (Grant Nos. 61505175 and 61475134) and the Natural Science Foundation of Hebei Province (Grant Nos. F2017203110 and F2017203193).

Abstract

A high-sensitivity refractive index (RI) sensor with wide tunable detection range based on the dual-core resonance of photonic crystal fibers are presented and studied by the finite element method. A cladding air hole coated with gold film is designed as the microfluidic channel for surface plasmon resonance sensing. The channel filled with liquid analyte acts as a defective core. The directional energy coupling between the fiber core and the defective core which determines the sensing performance is greatly influenced by both the RI of the filled liquid and the structural parameters. Numerical results show that the sensitivity of the sensor increases with the increase of the diameter of the analyte channel, and the RI detection range decreases with the increase of this diameter. So we tune the detection range by adjusting the diameter of the analyte channel to meet specific measurement requirements. As the diameter increases from 1.5 m to 2.4 m, the detection range shrinks from 1.45–1.62 to 1.45–1.48, both with the high spectral sensitivity 10 392 nm/RIU and 25 040 nm/RIU, respectively. The sensor with wide adjustable detection range shows great advantages in the field of biochemical, chemistry and environmental detection.