Controlled circular dichroism with graphene-based metamaterial for terahertz wave

Abstract This article explores the design and analysis of a metal-graphene hybrid metamaterial structure tailored for tunable circular dichroism (CD) effects in the terahertz (THz) frequency regime. Chiral metamaterials have garnered considerable interest in photonics due to their versatile applications, including sensing, polarization manipulation, and chiral imaging. The proposed metamaterial unit cell features four meta-atoms with C4 rotational symmetry, composed of gold on a polyimide substrate. By strategically integrating the graphene sheets above the gold patterns, selective control over the absorption efficiency for the incident wave of left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) light is achieved. The study demonstrates that adjusting graphene chemical potential enables precise modulation of CD from 0.80 to 0.10 across a wide THz frequency spectrum. Furthermore, the article investigates the structure optical response for incident angles ranging up to 75°, revealing stable CD behavior up to 30° and intriguing dual-band effects beyond 50°. These findings underscore the potential of the proposed metamaterial for practical applications in photonics, sensing, and chiral imaging, offering tunable control over the CD effects in the THz regime.