Terahertz sensor with parity time symmetry for enhanced detection of frozen oral cancer tissues

In this work, we present a defect-engineered one-dimensional photonic crystal (1D-PhC) operating in the terahertz regime, designed on the principle of parity-time (PT) symmetry for highly sensitive detection of frozen oral cancer cells. The proposed sensor is a one-dimensional parity–time-symmetric photonic crystal consisting of repeated silicon dioxide/porous silicon bilayers surrounding a central defect layer on a substrate, where the defect layer serves as the sensing region for frozen oral tissues. The transfer matrix method is employed to investigate the shift in the defect mode characteristics in the transmittance spectrum. By incorporating a complex refractive index distribution that fulfills PT-symmetric conditions, the system acquires non-Hermitian characteristics, resulting in sharp resonances and tunable defect mode responses. The simulation results reveal that the introduction of PT-symmetric gain and loss (Q) layers remarkably enhances the sensitivity compared to conventional PhC-based sensors. The proposed design achieves transmittance-based sensitivity of $$\:2.4\times\:{10}^{11}\:\%/RIU$$ and $$\:1.7\times\:{10}^{10}\:\%/RIU$$ , whereas spectra-based sensitivity of $$\:68.8\:GHz/RIU$$ and $$\:68.8\:GHz/RIU$$ for Q = 10.695 and 7.85, respectively. Along with its high sensitivity, the simplicity and fabrication feasibility of the structure make it a promising platform for real-time, label-free early-stage oral cancer detection.