Refractive index sensor for sensing high refractive index bioliquids at the THz frequency

Abstract

In this paper, a highly sensitive and low loss refractive index (RI) biosensor for high RI bio-analytes detection, such as for cholesterol, nicotine, and bacillus bacteria, is proposed. A novel, to the best of our knowledge, decagonal structure with porous core photonic crystal fiber (PC-PCF) is introduced. The porous core consists of a rectangular sensing hole. The analytes to be sensed are considered in liquid form and infiltrated into the sensing holes, which makes the sensing process simpler and more straightforward. Cladding of the PC-PCF consists of multilayer circular air holes arranged in a decagonal pattern. For durability and stability of the sensor, TOPAS is used as the fiber material. A perfectly matched layer is used for boundary conditions. The correlation among optical power, material, and structural properties is analyzed by the finite element method. The sensing performance of the designed sensor is observed at THz frequency (1.4–3.8 THz). The results under high RI of the analytes (1.52–1.55) are as follows: maximum sensitivity of 98.31% for x polarization and 98.26% for y polarization, very low confinement loss of 1.5 × 10 − 14 d B / m , narrow effective mode area of 1.92 × 10 − 7 m 2 , minimum effective material loss of 0.000164 c m − 1 , and very low waveguide dispersion of 0.002 ± 0.05 ps/THz/cm. In addition, the effect of variation of structural parameters on sensor performance is also analyzed. The proposed PC-PCF-based biosensor can be very useful for sensing higher RI biochemical analytes.