Terahertz ultrasensitive dual-core photonic crystal fiber microfluidic sensor for detecting high-absorption analytes

In this paper, we propose an ultrasensitive microfluidic refractive index sensor for detecting high-absorption analyte. The sensor is based on heterogeneous dual-core photonic crystal fiber structure and operates in the terahertz (THz) regime. ZeonexE48R is chosen as the background material. The dual-core structure is composed of the gradient porous core and the microfluidic channel. Simulation results show that before infiltrating a liquid analyte, a highly stable modal birefringence can be obtained around 2.0×10^-2 from 0.5 to 2 THz, along with the effective material losses of less than 0.182/cm for both the x- and y-polarization modes. After infiltration, this device can be employed for accurate refractive index (RI) sensing owing to the cross point selective coupling effect between the two core modes. This sensor offers RI sensitivities of 78.095 THz/RIU and 110.931 THz/RIU within dynamic measurement ranges from 1.41 to 1.429 for x-polarization mode and from 1.435 to 1.449 for y-polarization mode, respectively, and the measurable refractive index range reaches 0.0327. Our research gives a unique insight into the sensing mechanism for detecting high-absorption analyte in the THz band, which has broad application prospects for high-accuracy dynamic sensing in the fields of chemistry, biomedicine, and real-time environmental monitoring.