A temperature-tunable chirality-selective meta-absorber for electromagnetic encrypted imaging

Metamaterial-based technologies offer opportunities to realize spin-selective encryption platforms for key encoding, yet the flexibility and controllability of encrypted imaging are not satisfactory well enough. In this paper, we propose a temperature tunable chirality-selective meta-absorber based on the thermal phase change material of vanadium dioxide (VO2). The meta-absorber has the functionality of spin-selective absorption in high temperature, which enables perfect absorption at resonant frequency for one spin state of light, and a little loss for the other, resulting in a significant absorption circular dichroism (CD). The CD can be actively manipulated by ambient temperature (i.e., conductivity of VO2). Importantly, spin-encoded near-field imaging of letters and quick response codes are achieved using the CD effect of VO2 resonators and their enantiomers. The image contrast decreases with the reduction of ambient temperature and disappears at room temperature, which enables thermal-control electromagnetic encrypted imaging and hiding. This work provides a route for the development of tunable chiroptical systems, information encryption technologies, and temperature-control imaging devices.