High-Efficiency Graphene-Based Terahertz Polarization Converter with Integrated Biological Sensing and Tunable Performance

Despite recent advancements in terahertz metasurface engineering, most polarization converters remain limited in bandwidth, tunability, and multifunctional capability. In this study, we present a graphene-integrated reflective metasurface that addresses prior limitations by achieving ultraefficient broadband linear-to-cross-polarization conversion combined with high-performance sensing capability. The proposed design delivers polarization conversion ratios (PCR) above 90% from 10.408 THz to 21.524 THz, offering an exceptional bandwidth of 11.116 THz with a polarization conversion average of 98.13%. Within the sub-band of 10.716–21.314 THz, the PCR remains above 96% with an improved average of 98.37%. Additionally, the design exhibits PCR exceeding 98% over 6.244 THz across segmented frequency windows, peaking at an average of 99.13%, and reaches maximum values beyond 99.99% at specific resonances. The design sustains excellent performance under oblique excitation by retaining polarization conversion averages of 95.34% and 96.13% at 30° incidence across the respective broadband and high-efficiency windows. Tunability is achieved through dynamic control of the graphene Fermi level that enables real-time spectral reconfiguration. The device proves a high sensitivity to minute variations in chemical and biological samples. It successfully identifies key disease signatures such as malaria, breast cancer, cervical cancer, and glucose anomalies with a maximum sensitivity of 3.40 THz/RIU. This convergence of broadband polarization conversion, dynamic reconfigurability, and high sensing functionality establishes the proposed design as a high-potential candidate for integrated terahertz systems.