Vanadium dioxide (VO₂) is a temperature phase change material that has metallic properties at high temperatures and insulation properties at room temperature. In this article, a novel device has been designed based on the dielectric metasurface consisting of VO₂ and graphene array, which can achieve multiple functions by adjusting temperature and voltage. When the temperature is high (340 K), the device is in the absorption state and its absorptivity can be dynamically controlled by changing the temperature. On the other hand, the device is in the polarization state under room temperature, and the polarization of electromagnetic waves can be dynamically controlled by adjusting the voltage of graphene. This device can achieve a broadband absorber (the maximum absorptance reaches 99.415% at wavelengths ranging from 44 THz to 52 THz) and high polarization conversion efficiency (>99.89%) in the mid-infrared range, which has great advantages over other single-function devices. Our results demonstrate that this multifunctional device may have widespread applications in emitters, sensors, spatial light modulators, IR camouflages, and can be used in thermophotovoltaics and wireless communication.

Multifunctional metasurfaces play an important role in the development of integrated optical paths. However, some of the realizations of current multifunctional metasurface devices depend on polarization selectivity, and others change the polarization state of the outgoing light. Here, based on vanadium dioxide (VO₂) phase change material, a strategy to design a meta-duplex-lens (MDL) is proposed and numerical simulation calculations demonstrate that at low temperature (about 300 K), VO₂ behaves as a dielectric so that the MDL can act as a transmission lens (transmission efficiency of 87.6%). Conversely, when VO₂ enters the metallic state (about 355 K), the MDL has the ability to reflect and polymerize electromagnetic waves and works as a reflection lens (reflection efficiency of 85.1%). The dielectric waveguide and gap-surface plasmon (GSP) theories are used in transmission and reflection directions, respectively. In order to satisfy the coverage of the phase gradient in the range of 2π in both cases, we set the antenna as a nanopillar with a high aspect ratio. It is notable that, via symmetrical antennas acting in concert with VO₂ phase change material, the polarization states of both the incident light and the outgoing light are not changed. This reversible tuning will play a significant role in the fields of imaging, optical storage devices, communication, sensors, etc.

Optical vortex is a structured beam with a spiral phase wavefront. Different orbital angular momentums (OAM) are orthogonal to each other and multiplexed together without crosstalk. Vortex optical communication (VOC) can obtain good bandwidth and channel number. In this paper, we creatively exchanged the order of the spatial light modulator (SLM) and the optical switch, the communication link from "Vortex after Modulation (VAM)" to "Vortex Modulation (VM)", which constitutes a new link structure. Compared with the VAM communication link, the VM link has the advantages of higher transmission rate, better signal quality, lower signal error rate and so on. The results show that the VM link is 0.126 Gbit/s faster than the VAM on a single channel link, and 15.5 Gbit/s faster in 16-QAM 8 OAM beams multiplexing. The error rate of the received signal under the same conditions at the transmitting end has an improvement of 2~4 orders of magnitude. The method is simple, convenient to implement, and has a significant improvement in transmission rate. It can provide a wide range of applications in vortex high-capacity communication.