Harnessing PT Symmetry in 1D Defective Photonic Crystals for Enhanced Sensing

In this work, a one-dimensional defective photonic crystal (1D DPhC) is proposed for THz sensing applications. The sensor comprises alternating SiO ₂ and Si dielectric layers. Defective layers are placed at the centre of the periodic structure, forming a cavity sandwiched between SiO ₂ layers on both sides. The cavity within the defective layers is infiltrated with aqueous polyethylene glycol at various concentrations. The transfer matrix method is employed to investigate the transmission of the proposed sensor. The performance of the proposed THz sensor is evaluated using multiple metrics, including sensitivity, figure of merit, Q-factor, and detection limit. Additionally, the efficacy of the proposed THz sensor is enhanced by integrating a parity-time (PT) symmetric structure into DPhC. The detailed numerical results corroborate the conclusion that the 1D DPhC constructed on a PT-symmetric structure exhibits improved sensing performance compared with the traditional 1D DPhC. The study also examines how the geometrical factors, namely the thickness and periodicity of the defective layer, influence sensor metrics. The proposed THz sensor, utilising a PT-symmetric design, offers outstanding detection capabilities.