Chiral metasurface for narrowband mid-IR circular dichorism

• Main Author: Dai, Shuqin
• Other Authors: Wang Qijie
• Format: Thesis-Master by Coursework
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/167980
• Institution: Nanyang Technological University

The present study focuses on employing chiral structure to distinguish between right circular polarized (RCP) and left circular polarized (LCP) magnetic waves based on chiral structure’s distinct absorb spectra towards these polarized waves. Prior research in the mid-infrared region has demonstrated wide band circular dichroism (CD) using 3D or multilayered metamaterials. Metamaterials face significant challenges in practical applications due to complex fabrication processes, scalability issues, and high costs. The fabrication of metamaterials requires the development of novel techniques, as well as access to limited materials for the production of intricate structures. In contrast, the present study investigates the chiral structure design of monolayer metasurfaces, which can be readily produced using conventional nanofabrication techniques. The chiral metasurfaces exhibit exceptional Circular Dichroism (CD) with the highest result CD > 0.8 and a narrow line width with quality factor of approximately 1000. This study fills the gap in the limited research on narrow band CD in the mid-infrared (MIR) region. The CD of the chiral structure can be tuned by adjusting the asymmetry parameter, and by varying the period parameter. The results of this study could have significant implications in the field of photonics and spectroscopy. The ability to distinguish between different polarized waves with high accuracy could lead to the development of new optical devices with a broad range of applications. The tunability of the CD through adjustments to the structural parameters of the chiral structure may also facilitate the design of more efficient and adaptable optical devices.