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.