Hao-Miao Zhao, Xinyang Wang, Qi Lin, Xiang Zhai, Guidong Liu
Abstract In this study, we propose a dynamically tunable dual-functional polarization converter utilizing a monolayer cross-shaped borophene metasurface for efficient cross-polarization conversion within optical communication bands. The underlying polarization conversion mechanism, driven by the synergistic interaction between Fabry–Pérot cavity resonance and borophene localized surface plasmon resonance, is thoroughly elucidated. The designed cross-shaped borophene metasurface achieves near-ideal linear-to-linear (LTL) polarization conversion, with a polarization conversion ratio (PCR) exceeding 0.98 across the operating bandwidth and reaching nearly 1.0 at a wavelength of 1380 nm. Dynamic tuning of the resonant wavelength can be achieved by modulating the carrier density of borophene while maintaining a high PCR. The operational wavelength range can be further extended through co-optimization of the dielectric layer thickness. Moreover, the proposed metasurface not only supports x-y cross polarization conversion (CPC) but also enables dual-channel linear-to-circular (LTC) polarization conversion with a polarization extinction ratio (PER) as high as 80 dB. Dynamic switching between LTL and LTC functional modes is also demonstrated. Wavelength multiplexing of these functionalities is also successfully achieved. The device exhibits robust angular stability, maintaining PCR > 0.9 and PER > 40 dB under oblique incidence up to 50°. Owing to its compact configuration and versatile tunability, this design provides a promising platform for developing multifunctional and reconfigurable photonic devices applicable in optical communications, imaging, and sensing systems.