▎ 摘　　要

We propose a frequency-tunable and functionality-switchable polarization conversion device in transmission mode by integrating a silicon strip array with a graphene sheet in the mid-infrared region. High cross-polarization transmission, together with the dynamic frequency shift, contributes to a frequency-tunable half-wave plate working from 17.6 to 17.8 THz. Simultaneously, the device can act as a switchable polarizer to selectively generate co-or cross-polarized light by combining the frequency-tunability and a sharp x-shape polarization transmission caused by hybrid Mie resonances. Furthermore, this graphene-based metasurface also realizes continuous 180-degree phase modulation by electrically controlling graphene. The transmitted frequency-tunable and functionality-switchable device with simple-shape inclusions achieves multiple polarization conversions for both linearly and circularly polarized light without refabricating the geometric parameters, which represents a significant advance compared with previously reported counterparts. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement