Broadband Cross-Polarization Conversion in a Graphene-Assisted Metasurface for Chemical Detection

A graphene-integrated reflective design is proposed that breaks the bandwidth, tunability, and single-function limits of typical terahertz polarization converters. The structure achieves linear-to-cross conversion above 90% from 9.823 to 17.844 THz with an 8.021-THz span and a mean polarization conversion of 98.93%. Within 10.08–17.71 THz, polarization conversion ratio (PCR) remains above 95% with a 99.25% average while segmented windows totaling 7.2 THz exceed 98% with 99.40% average and peak values surpass 99.99% at multiple resonances. Performance is stable under oblique incidence retaining band-averaged PCRs of 98.21% and 98.49% at 24°. Real-time reconfiguration is aided through electrical control of the graphene Fermi level requiring no geometric change. As a sensor, the design resolves small refractive-index shifts with a maximum sensitivity of 2.20 THz/RIU and differentiates representative chemical analytes through consistent frequency shifts. The combined attributes of ultraefficient broadband conversion, strong angular tolerance, electrical tunability, and high sensing accuracy establish this design as a compact and fabrication-friendly candidate for integrated terahertz polarization control and chemical sensing.