Using Thue Morse structure and magnified defect resonance as cancer sensor

This paper examines the properties of quasi-periodic photonic crystals to develop biomedical sensors for oral cancer detection, utilizing parity-time symmetry conditions. A photonic crystal structure based on the Thue-Morse sequence utilizing silicon dioxide (SiO₂) and silicon (Si) is proposed. This structure comprises a defect layer containing healthy or cancerous cell samples inserted in the center between two identical Thue-Morse structures. The main objective is to analyze the transmittance spectra of the proposed system using the transfer matrix method with MATLAB simulation. The effects of various parameters, including period number, defect thickness, and the refractive index of the silicon dioxide complex, were analyzed to optimize sensor sensitivity. Due to the high absorption properties of normal and cancerous cells, the associated confined resonant mode exhibits very low transmittance. To solve this problem, a parity-time symmetry optimization technique was employed in the Terahertz band to selectively amplify the resonant mode. The results show that the gain/loss factor is a critical parameter for amplifying the resonance mode transmittance within the photonic band gap. The optimized sensor exhibited a remarkable resonance peak magnification, achieving a transmittance of 3.16 × 10⁹% with an extremely high sensitivity of 9.0 × 10⁹%/RIU for cancer cell detection. These results demonstrate that the proposed quasi-periodic structure with Parity-time symmetry enables sensitive distinction of pathological tissues, primarily due to its resonant spectral response. This underlines its potential application in the precise optical detection of oral cancer.