Article
Optics
Xingyuan Zhang, Wenqiao Shi, Jianqiang Gu, Longqing Cong, Xieyu Chen, Kemeng Wang, Quan Xu, Jiaguang Han, Weili Zhang
Summary: This study demonstrates multiple bound states in the continuum (BICs) in a terahertz metasurface consisting of metallic split ring resonators (SRRs). The evolution from BICs to quasi-BICs (QBICs) is achieved by varying the gap width of the SRRs. Experimental results show that the leakage behavior of these QBICs is strongly influenced by the intrinsic Ohmic loss in the SRRs, while it is robust to tilted incidence.
Article
Optics
Dejun Liu, Xi Yu, Feng Wu, Shuyuan Xiao, Fumihiro Itoigawa, Shingo Ono
Summary: This study demonstrates a laser-fabricated metallic resonator based on a double-slit array (DSA) at terahertz frequencies, showing sharp resonances with high Q-factors. By breaking the structural symmetry of DSAs, the infinite Q-factor bound states in the continuum (BIC) can be transformed into quasi-BICs, with Q-factors decreasing gradually as asymmetry parameter increases. The influence of imperfections in experimental samples on the transmission properties of DSAs and the effect of metal thickness on the quasi-BICs are also investigated, indicating potential practical applications in electromagnetic wave filtering and biomolecular sensing.
Article
Optics
Laura Pilozzi, Mauro Missori, Claudio Conti
Summary: In this study, the transition from Fano resonances to Bound states in the continuum (BIC) in a one-dimensional photonic crystal slab made of rectangular dielectric rods was investigated at terahertz frequencies. Symmetry-protected, high-Q BIC were found at normal incidence through simulations based on an analytical exact solution of the Maxwell equations. For non-normal incidence, BIC coupled with freely propagating waves and appeared as Fano resonances in the scattering field. The simulations were validated by 3D-printing the photonic crystal slab and comparing THz time-domain spectroscopy measurements.
Article
Nanoscience & Nanotechnology
Tailin Zhang, Xingyuan Zhang, Yun Shen, Yinsheng Xu, Laibin Luo, Jianqiang Gu, Sijia Yang, Jie Xu, Xiaohua Deng
Summary: In this study, a terahertz BIC metasurface structure composed of metal split ring resonators (SRRs) was designed. The leakage process of BIC states to the far field was studied by changing the gap width of SRR based on the symmetric protection principle of superlattice mode. By introducing multiple SRRs and changing their arrangement, three superlattice modes and BIC states were obtained. Experimental observations confirmed the leakage of BIC states into the far field, forming observable quasi-BIC patterns. A feasible method for flexible design and implementation of BIC was verified.
Article
Optics
Wenbin Ma, Chaobiao Zhou
Summary: In this work, we investigate the excited properties of quasi-bound states in the continuum (QBICs) in highly symmetrical silicon nanodisks with double notches on the edges. We find that QBICs exhibit the same optical response under s-polarized and p-polarized light, and the highest coupling efficiency occurs at a polarization angle of 135 degrees. The QBICs are dominated by the magnetic dipole along the z direction, as confirmed by near-field distribution and multipole decomposition. Experimental results show a sharp Fano resonance with a Q-factor of 260, indicating promising applications in enhancing light-matter interaction.
Article
Nanoscience & Nanotechnology
Weronika Glowadzka, Michal Wasiak, Tomasz Czyszanowski
Summary: This study explores the possibility of realizing bound states in the continuum (BICs) in systems with broken symmetry, demonstrating that high-quality factor BICs can be achieved in gratings with broken up-down mirror symmetry. The research also shows potential for creating micro- and nanooptical cavities in standard all-semiconductor technology with Q-factors above 10^4.
Article
Crystallography
Yaolin Hu, Suxia Xie, Chongjun Bai, Weiwei Shen, Jingcheng Yang
Summary: In this study, a chiral quasi-BIC is proposed by breaking the out-of-plane mirror and in-plane C-2 rotation symmetries in a bilayer metallic metasurface, which enables spin-selective terahertz transmittance. Precise tuning of structural parameters allows for anticipated chiroptical performance, and a high surrounding refractive index sensitivity is achieved.
Article
Nanoscience & Nanotechnology
Yi Zhou, Man Luo, Xuyang Zhao, Yuxiang Li, Qi Wang, Zhiran Liu, Junhong Guo, Zhihe Guo, Junjie Liu, Xiang Wu
Summary: Asymmetric metasurfaces supporting quasi-bound states in the continuum (BICs) have high Q-factors and strong light-matter interaction properties, making them attractive for label-free biosensing applications. This study compared several meta-atom geometries to determine the most practical choice for biosensing. The tetramer meta-atom design was found to have higher surface sensitivity and a larger size-to-wavelength ratio, while a greater depth enhanced surface sensitivity. Experimental demonstration of two asymmetric tetramer metasurfaces showed sharp high Q-factor resonances and polarization-insensitive features, with the thicker metasurface exhibiting higher surface sensitivity. These findings open new possibilities for high-performance biosensing and chemical-sensing applications.
Article
Multidisciplinary Sciences
Yuhang Ruan, Yuke Li, Zhengda Hu, Jicheng Wang, Yixiang Wang
Summary: This paper investigates optical bound states in the continuum (BICs) in photonic crystals and periodic structures, which can be used for narrowband transmission filters, lasers, and sensors. The study analyzes the energy bands of a complex structure consisting of a grating and a multilayer substructure to determine the position of the BIC. By using transmission matrix theory, the study examines wave propagation and the change in Q value. The reflectance spectrum exhibits asymmetric line-shapes due to interference between two channels, and quasi-BICs transform into BICs as the asymmetry parameter decreases. The work designs a complex structure with ultrahigh Q factor and strong resonance properties, contributing to the exploration of BIC phenomena.
SCIENTIFIC REPORTS
(2022)
Article
Physics, Multidisciplinary
Adam Overvig, Nanfang Yu, Andrea Alu
Summary: The study introduces quasi-bound states in the continuum (QBICs) born of chiral perturbations, encoding arbitrary elliptical polarization states and enabling geometric phase engineering. Metasurfaces with ultrasharp spectral features are designed as a result, shaping impinging wave fronts with near-unity efficiency. The findings extend Fano resonances beyond their conventional limits, opening opportunities for nanophotonics, classical and quantum optics, and acoustics.
PHYSICAL REVIEW LETTERS
(2021)
Article
Optics
Zhongfu Li, Yuanjiang Xiang, Shixiang Xu, Xiaoyu Dai
Summary: This work proposes a thoughtful all-dielectric columns structure with broken symmetry to achieve ultrasensitive sensing in the terahertz range. Sensitivity to the surrounding media can be achieved by observing quasi-BIC resonances in the transmission/reflection spectrum.
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Yi Zhou, Zhihe Guo, Xuyang Zhao, Feilong Wang, Zhiyuan Yu, Yizhen Chen, Zhiran Liu, Shuyu Zhang, Shulin Sun, Xiang Wu
Summary: A new kind of all-metal metasurfaces has been designed and demonstrated, which can achieve high-Q and high figure of merit resonances based on bound states in the continuum. The devices can exhibit symmetry-protected and Friedrich-Wintgen quasi-BICs features simultaneously, leading to higher Q-factors than those inspired by single quasi-BIC. The utilization of a metal substrate instead of a dielectric one releases the constraint of symmetrical dielectric environment for common metasurfaces. The proof-of-concept experiments demonstrate the high performances of such dual quasi-BIC based plasmonic refractive index sensors.
ADVANCED OPTICAL MATERIALS
(2022)
Article
Optics
Jitao Li, Zhen Yue, Jie Li, Chenglong Zheng, Yating Zhang, Jianquan Yao
Summary: By breaking the in-plane C2 and mirror symmetries of a planar all-silicon THz metasurface, we construct quasi bound states in continuum (quasi-BIC) with high quality factor and ultra-low radiative loss, achieving customizable manipulation of THz chirality in an ultra-narrow bandwidth.
OPTICS AND LASER TECHNOLOGY
(2023)
Article
Optics
Meiqi Li, Qichang Ma, Aiping Luo, Weiyi Hong
Summary: This paper proposes an all-dielectric metasurface composed of a Si layer and three Si rectangular bars with different widths and lengths, which achieves triple high Q-factor and high tunable quasi bound states in the continuum (quasi-BIC) modes with distinct Fano features by breaking the rotational symmetry. By adjusting the asymmetry parameter, the modulation depth, resonant frequency, and linewidth of the sharp triple Fano resonances can be engineered, and the achieved Q-factor can reach 10^7. Moreover, the triple quasi-BIC modes are mainly generated by the toroidal dipole oscillation. The proposed nanostructure has potential applications in nonlinear optics, filters, and multi-channel biosensors.
OPTICS AND LASER TECHNOLOGY
(2022)
Article
Optics
A. S. Lal Krishna, Sruti Menon, Asish Prosad, Varun Raghunathan
Summary: We experimentally demonstrate a novel quasi-bound state in the continuum (BIC) resonance in the mid-infrared wavelength region. By confining the resonant electric field within a low-refractive-index medium, we achieve a slot-mode profile with high mode field confinement. The structure shows a high quality factor and tunable resonant wavelength, making it suitable for applications in sensing and active photonic devices.
PHOTONICS RESEARCH
(2022)
