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Dynamically tunable broadband absorber/reflector based on graphene and VO2 metamaterials.

We propose a difunctional tunable broadband absorber/reflector consisting of a periodic cross-shaped graphene array and a vanadium dioxide (VO2) layer. When VO2 reflects the properties of metal, the proposed dual-function device is used as a reflector; when VO2 reflects the nature of the dielectric, the difunctional device will be used as an absorber. The simulation results indicate that more than 90% absorption bandwidth can be available in the absorber in the frequency range of 56.1-59.0 THz, up to 100%. Moreover, over 80% absorption can be achieved over the frequency range of 88.5 to 90.2 THz. In addition, the bandwidth and absorption of the metamaterial absorber can be dynamically changed because of the Fermi energy level in graphene and the temperature tunability of VO2. The proposed device can be applied to manufacturing infrared spectrophotometers, on-dispersive infrared photometers, and Fourier transform infrared spectrometers. Therefore, it has potential application in the field of environmental monitoring.