Switchable terahertz chiral metasurface for linear and circular dichroism

An elaborately designed multifunctional metasurface based on vanadium oxide (VO 2 ) that enables polarization-selective modulation is presented. The metasurface is capable of transitioning between absorption and transmission modes by modulating the two-phase states of VO 2 . When VO 2 acts as a metal state, significant linear dichroism in the absorption mode (LD A ) is achieved with peak absolute values reaching 0.9 at 7.62 THz and 0.84 at 8.96 THz. Alternatively, when illuminated with circular polarized light, the absorption mode exhibits efficient circular dichroism (CD A ) over a broad frequency range from 2.96 THz to 6.32 THz, corresponding to a bandwidth of 3.36 THz. Upon transitioning VO 2 into its dielectric state, the metasurface displays multi-band transmission linear dichroism (LD T ) with a peak absolute value of 0.88. Additionally, it exhibits dual-band transmission circular dichroism (CD T ) with a maximum absolute value of 0.6. The underlying physical mechanism is elucidated through the application of impedance matching theory and analysis of electromagnetic field distribution. Remarkably, through the strategic arrangement of the original unit cells, their rotational variants, and mirror-image counterparts, we highlight the metasurface’s potential in digital imaging display and visualized polarization recognition.