In this research, an entirely novel optical sensor for alcohol detection based on quasi-shaped spectroscopy is offered. A quasi shape with a tightly bonded structure in the cladding region and a hexahedron core region makes up the recommended design, which has a remarkable sensitivity of about 91.35%, 92.55%, and 90.40%and low confinement losses (CLs) of 5.44 × 10⁻⁰⁸ dB/m, 6.75 × 10⁻⁰⁸ dB/m, and 5.85 × 10⁻⁰⁸ dB/m for detecting alcohol like ethanol (n = 1.354), butanol (n = 1.3993), and propanol(n = 1.384), at 1 THz. The numerical aperture, the effective area, and the V-parameter have all been identified and assessed. The 0.8THz to 3 THz operational wavelength range is stated. In the COMSOL Multiphysics (Version 5.6) environment, the properties of these suggested alcohol sensors are numerically examined utilizing the FEM (finite element method) with full vectors. In contrast to other efforts, the proposed sensor, which consists of a quasi-lattice PCF with a perfectly matched layer (PML) of a circular air hole shape and TOPAS as the background material, aims to improve sensitivity response. The proposed sensor might be crucial in the alcohol detection process due to its superior sensitivity response, a single mode of operation across the entire operational terahertz range, and shallow confinement loss. So, this PCF can proficiently be pragmatic in many biological sensing and other THz technology domains.