Terahertz broadband tunable chiral metamirror based on VO2-metal hybrid structure

Aiming at the problems of narrow working bandwidth, low efficiency, and complex structure of existing terahertz chiral absorption, we propose a chiral metamirror composed of C-shaped metal split ring and L-shaped vanadium dioxide (VO2). This chiral metamirror is composed of three layers of structure, a gold substrate at the bottom, the first polyethylene cyclic olefin copolymer (Topas) dielectric layer and VO2-metal hybrid structure as the top. Our theoretical results led us to show that this chiral metamirror has a circular dichroism (CD) value greater than 0.9 at 5.70 to 8.55 THz and has a maximum value of 0.942 at f = 7.18 THz. In addition, by adjusting the conductivity of VO2, the CD value can be continuously adjustable from 0 to 0.942, which means that the proposed chiral metamirror supports the free switching of the CD response between the on and off states, and the CD modulation depth exceeds 0.99 in the range of 3 to 10 THz. Moreover, we discuss the influence of structural parameters and the change of incident angle on the performance of the metamirror. Finally, we believe that the proposed chiral metamirror has important reference value in the terahertz range for constructing chiral light detectors, CD metamirrors, switchable chiral absorbers and spin-related systems. This work will provide a new idea for improving the terahertz chiral metamirror operating bandwidth and promote the development of terahertz broadband tunable chiral optical devices.& COPY; 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

In this study, a chiral subwavelength mirror composed of C-shaped metal split ring and L-shaped vanadium dioxide (VO2) is proposed to address the issues of narrow working bandwidth, low efficiency, and complex structure in existing terahertz chiral absorption. Theoretical results show that the chiral metamirror exhibits a circular dichroism (CD) value greater than 0.9 at 5.70 to 8.55 THz, with a maximum value of 0.942 at f = 7.18 THz. By adjusting the conductivity of VO2, the CD value can be continuously adjustable from 0 to 0.942, allowing for free switching of the CD response between the on and off states. Additionally, the CD modulation depth exceeds 0.99 in the range of 3 to 10 THz. The proposed chiral metamirror has important reference value in the terahertz range for constructing chiral light detectors, CD metamirrors, switchable chiral absorbers, and spin-related systems. This work provides a new idea for improving the terahertz chiral metamirror operating bandwidth and promotes the development of terahertz broadband tunable chiral optical devices.