This paper presents an analysis on a hexagonal cladding with a rotated-hexa core in photonic crystal fiber (H-PCF) based optical sensor formation with simultaneously minimal confinement loss and higher sensitivity for chemical sensing functions. The numerical assessment of the designed structure is achieved with the procedure of finite element method (FEM) and perfectly matched layers (PML) boundary condition in the comsol multiphysics software tool. As per FEM numerical analysis, the proposed PCF sensor presents the extreme relative sensitivity at 81.46%, 82.26% and 79.22% for three chemicals at 1 terahertz (THz) such as Ethanol (n = 1.354), Benzene (n = 1.366) and Water (n = 1.330), respectively. Moreover, at 1 terahertz (THz) the low confinement losses are 5.85 × 10−08, 6.07 × 10−08 and 5.84 × 10−08 dB/m for similar three chemicals. The effective area, the effective mode index and the total power fraction are also elaborately explained. Furthermore, we hope that our proposed structure can be operated intensely in the field of biomedical, bio-sensing experiments and industrial applications in terahertz (THz) waveguide technology.