Terahertz spectroscopic based bending effect inspection on hollow-core anti-resonant fiber

In this study, a Hollow-Core Anti-Resonant Fiber (HC-ARF) for gas sensing purposes with ultra-high sensitivity responses and the fiber bending effects on sensing parameters have been investigated. The findings are based on the computer simulations run in COMSOL Multiphysics (version-5.3a) software which implements Finite Element Methods (FEM). The proposed optimized structure contains a large hollow core and six thin-walled capillaries. The proposed HC-ARF-based sensor also shows very low loss profiles. The values of propagation losses (mainly confinement loss) and material absorption loss of the sensor are in the order of 10(-3). The maximum relative sensitivity response is 99.95%. As the fiber core is relatively large, fundamental modes (horizontally polarized mode and vertically polarized mode) and also a few Higher Order Modes (TM01 mode, TE01 mode, HE21 (even) mode, HE21 (odd) mode, etc.) are observed. But the fiber sensor also has a good Higher Order Mode suppression ratio (HOMER) response. Along with short-distance gas sensing, it can be used for long-distance sensing as well as transmission purposes with single-mode propagation. At the end of the article, the bending effects on relative sensitivity and propagation losses have also been demonstrated in detail when the fiber is bent with various bend-radii. It is observed that bending introduces sensitivity drops.