High-Q terahertz chirality enhancement using elliptical hole metasurface

IF 2.2 3区物理与天体物理 Q2 OPTICS Optics Communications Pub Date : 2024-11-02 DOI:10.1016/j.optcom.2024.131268

Hongyan Yang , Hongrui Sun , Yuhang Yang , Quanlin He , Jianqing Li , Gongli Xiao

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Abstract

Circular dichroism (CD) technology has garnered significant attention due to its extensive applications in ultra-sensitive biosensing and spin-selective optical frequency conversion. However, existing terahertz chiral structures are constrained by linewidth, which limits their effectiveness in narrowband signal processing. In this study, we propose the notion of quasi-bound states in the continuum (quasi-BIC) within a planar elliptical hole all-silicon terahertz metasurface that exhibits broken mirror symmetry. This approach achieves a CD value as high as 0.97, with a linewidth below 0.5 GHz and a Quality (Q)-factor reaching up to 10⁷ in the 1.3 THz to 1.55 THz band, thereby enabling ultra-narrowband terahertz chirality. This method significantly enhances the Q-factor of optical resonant systems, reduces linewidth, and achieves strong CD while addressing the trade-off between high Q-factor and high CD observed in existing structures. The theoretical foundations for achieving ultra-narrow linewidth are established through band structure calculations and far-field polarization analysis. Additionally, the Q-factor of quasi-BIC can be flexibly optimized through parameter tuning, rendering it more practical than perfect BIC in real-world applications. This study presents a novel solution for terahertz narrowband chirality and optical filters, potentially advancing technologies in related fields.

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利用椭圆孔元表面增强高 Q 太赫兹手性

圆二色性（CD）技术在超灵敏生物传感和自旋选择性光频转换方面应用广泛，因而备受关注。然而，现有的太赫兹手性结构受到线宽的限制，从而限制了其在窄带信号处理中的有效性。在本研究中，我们提出了在平面椭圆孔全硅太赫兹元表面内的连续体中准束缚态（quasi-BIC）的概念，该平面椭圆孔全硅太赫兹元表面表现出破碎的镜像对称性。这种方法实现了高达 0.97 的 CD 值，线宽低于 0.5 GHz，在 1.3 THz 至 1.55 THz 波段的质量（Q）因子高达 107，从而实现了超窄带太赫兹手性。这种方法大大提高了光学谐振系统的 Q 因子，降低了线宽，并实现了强 CD，同时解决了现有结构中存在的高 Q 因子和高 CD 之间的权衡问题。通过带状结构计算和远场偏振分析，建立了实现超窄线宽的理论基础。此外，准 BIC 的 Q 因子可通过参数调整灵活优化，在实际应用中比完美 BIC 更为实用。这项研究为太赫兹窄带手性和光学滤波器提出了一种新的解决方案，有望推动相关领域技术的发展。© 2024 Optica Publishing Group，根据 Optica Publishing Group Open Access Publishing Agreement 的条款。

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来源期刊

Optics Communications 物理-光学

CiteScore

5.10

自引率

8.30%

发文量

681

审稿时长

38 days

期刊介绍： Optics Communications invites original and timely contributions containing new results in various fields of optics and photonics. The journal considers theoretical and experimental research in areas ranging from the fundamental properties of light to technological applications. Topics covered include classical and quantum optics, optical physics and light-matter interactions, lasers, imaging, guided-wave optics and optical information processing. Manuscripts should offer clear evidence of novelty and significance. Papers concentrating on mathematical and computational issues, with limited connection to optics, are not suitable for publication in the Journal. Similarly, small technical advances, or papers concerned only with engineering applications or issues of materials science fall outside the journal scope.