Terahertz image encryption based on chiral metasurface

• This research proposes a chiral metasurface operating in the 0–1 THz range, which exhibits high circular dichroism and enables selective absorption of left- and right-handed circularly polarized waves, demonstrating potential applications in image encryption technology. • The chiral metasurface exhibits symmetric absorption characteristics with its mirror-image structure. The original structure achieves a CD value of 0.80 at the resonant frequency of 0.447 THz, while the mirror-image structure yields a CD value of −0.80 at the same frequency. Furthermore, the performance of this structure has been validated through experimental measurements. • By introducing the multiple interference model and the exceptional point theory, we thoroughly analyzed and academically validated the mechanism behind the selective absorption characteristics exhibited by the chiral metasurface, thus demonstrating the reliability of the design. • This research proposes an image-encryption metasurface constructed based on unit cells with various geometric parameters of the chiral metasurface. It enables distinct image outputs under incident waves with different polarization states, demonstrating its potential for applications in the field of image encryption. Images, as prevalent carriers of information, are widely applied in daily life and production. With the development of information technology, concerns over information security have risen, leading to the emergence of image encryption techniques. Metasurfaces demonstrate exceptional electromagnetic wave manipulation capabilities, establishing their potential as encryption platforms for image security. In this work, a chiral metasurface that exhibits completely opposite absorption characteristics for circularly polarized waves in its original and mirror-image configurations is experimentally demonstrated. Then, both the multiple interference model and exceptional point are used for theoretical analysis of the chiral metasurface. Finally, the polarized-dependent metasurface encryption image is designed to achieve different terahertz images based on the chiral structures.