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. [ABSTRACT FROM AUTHOR]