Tunable dual-band asymmetric transmission and quad-band circular dichroism in graphene-hybridized y- shaped terahertz metamaterial

Abstract We present a y -shaped metasurface structure integrated with dual U-shaped rings. This structure can excite two resonance modes under linearly polarized wave incidence at 0.28 and 0.49 THz, meanwhile the x -and y -polarized AT values reach up to 0.73 and 0.62 at the two resonant frequencies, respectively. As we know, the linearly polarized wave is a degenerate mode and it can be decomposed into LCP and RCP components with equal amplitude and opposite helicity. Herein, when the incident wave is LCP and RCP, the above two resonance modes undergo degeneracy breaking around 0.28 and 0.49 THz, ultimately forming the independent resonances at 0.26 (0.46) and 0.31 (0.50) THz for RCP and LCP, respectively. As a result, quad-band CD effects achieved at the four resonant frequencies, with values of 0.49, 0.46, 0.56 and 0.64, respectively. Dynamic modulation of the amplitude and frequency response of both AT and CD effects are enabled by adjusting the Fermi energy level of the graphene. This design provides a novel approach for developing multifunctional tunable chiral devices, with potential applications in terahertz communications, biosensing, and polarization control technologies.