Nolvel photonic crystal fiber biosensors for detecting volatile organic compounds in the terahertz region

This paper proposes a photonic crystal fibre (PCF) sensor designed for detecting volatile organic compounds (VOCs), specifically benzene, toluene, and p-xylene, within the terahertz frequency range of 0.6 to 3.0 THz. The sensor features a large circular core holes and two layers of circular air holes arranged in a circular lattice, which enhances light-analyte interaction and optical confinement. The design and numerical analysis were conducted using COMSOL Multiphysics (version 5.6) with the finite element method (FEM) to evaluate key optical properties, including effective refractive index, relative sensitivity, power fraction, confinement loss, effective area, and numerical aperture. The results indicate that at an optimum frequency of 1.0 THz, the proposed sensor achieves high relative sensitivity values of 99.6% for benzene, 99.92% for toluene, and 99.91% for p-xylene, with ultra-low confinement losses in the order of 10^–13 to 10^–14 dB/m. These findings demonstrate the sensor’s potential for highly sensitive VOC detection in industrial and medical applications. Moreover, the simplicity of the PCF structure enhances its feasibility for fabrication and practical implementation.