Tunable Control of Mie Resonances Based on Hybrid VO2 and Dielectric Metamaterial

Polarization-controlled varifocal metalens with a phase change material GSST in mid-infrared

Detection of aldehyde carbonyl radiation plays an essential role in guaranteeing the safety of fried food. However, the radiation of low-content aldehyde carbonyl is always weak and includes polarized light. Focusing the weak radiation with polarization-sensitive configurations provides an efficient way to improve the signal-to-noise ratio of detection. The advent of dynamic metasurfaces based on phase-change materials (PCMs) have demonstrated superiorities over their traditional counterparts in tunability and miniaturization. In this paper, we propose two reflected varifocal metasurfaces, which combine Ge₂Sb₂Se₄Te₁ (GSST) with two materials that have close optical constants with amorphous and crystalline GSST. The first one realizes a four-spot focal system with linearly-polarized incidence based on polarization multiplexing. It adds a new polarization degree of freedom compared with traditional varifocal metasurfaces. Compared with traditional spatial-multiplexing method, our second metasurface enables the independent control of the polarization and phase profiles of circularly-polarized light. Remarkably, it reduces energy loss and crosstalk. We believe the novel scenarios of combing GSST with similar materials provide a new direction for tunable metasurfaces based on PCMs.

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.