Graphene-enhanced non-Hermitian Thue–Morse metamaterial sensor exploiting exceptional point for cancer biomarker detection

We present a one-dimensional photonic crystal biosensor based on a Thue–Morse quasi-periodic structure incorporating parity–time (PT) symmetry and exceptional point (EP) engineering for enhanced cancer detection. By integrating alternating porous silicon gain–loss layers with graphene nanolayers, the proposed design achieves strong optical confinement and pronounced resonance sharpening near EP conditions. A systematic parametric study identified the optimal graphene chemical potential and relaxation time as 0.408 eV and 0.5 ps, respectively, leading to a maximum sensitivity of 1054 nm/RIU and a minimum detection limit of 9.875 × 10 − 4 RIU. Moreover, the analysis reveals that increasing the number of graphene layers results in a progressive enhancement in sensitivity accompanied by a reduction in the optimal porosity percentage, highlighting the strong influence of graphene-induced field confinement on device performance. These results surpass those of conventional one-dimensional biosensors, demonstrating the combined advantages of PT symmetry and graphene-assisted field enhancement. Fabrication tolerance analysis confirmed the structural robustness, underscoring its potential for practical implementation. Overall, the findings establish PT-symmetric Thue–Morse photonic crystals as a versatile platform for ultra-sensitive, label-free biomedical sensing, paving the way for next-generation optical diagnostic technologies.