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Nanophotonics, Metamaterials, and Plasmonics|76 Article(s)
Bending-switchable terahertz metamaterial with a single layer based on laser-induced graphene
Abdul Jalal, Yan Dong, Bowen Deng, Muhammad Qasim, Mojtaba Moghaddasi, Ubaid Ur Rahman Qureshi, Zongyuan Wang, Xudong Wu, Chenjie Xiong, and Bin Hu
We propose a fast-printable and function-switchable metamaterial based on laser-induced graphene for terahertz (THz) wave modulation in the reflection mode. The design can modulate the linear polarization of the incoming wave fronts to its cross-polarization from 0.27 to 0.41 THz and linear polarization to circular polarization from 0.48 to 0.62 THz. The function of the device can also be switched from a polarization converter to an absorber by bending it with an angle of 57°. Experimental results showed a good agreement with those of the simulation. The proposed polarization converter may find its application in THz polarization control systems and sensing. We propose a fast-printable and function-switchable metamaterial based on laser-induced graphene for terahertz (THz) wave modulation in the reflection mode. The design can modulate the linear polarization of the incoming wave fronts to its cross-polarization from 0.27 to 0.41 THz and linear polarization to circular polarization from 0.48 to 0.62 THz. The function of the device can also be switched from a polarization converter to an absorber by bending it with an angle of 57°. Experimental results showed a good agreement with those of the simulation. The proposed polarization converter may find its application in THz polarization control systems and sensing.
Chinese Optics Letters
- Publication Date: Apr. 16, 2025
- Vol. 23, Issue 4, 043603 (2025)
Evolution of multipeak spectral features in SERS reveals atomic-scale structural fluctuations in plasmonic nanocavities
Wenjin Zhou, Lei Xi, Min Yang, Guofeng Zhang, Chengbing Qin, Jianyong Hu, Yao Zhang, Ruiyun Chen, Liantuan Xiao, and Suotang Jia
In this study, we investigate the intensity and spectral fluctuations in surface-enhanced Raman scattering (SERS) signals from individual plasmonic nanocavities. Extremely long-duration blinking components lasting up to minutes are observed in the SERS intensity fluctuation at room temperature, which can be characterized by successive and random appearance and eventual disappearance of multiple vibrational modes at different frequencies. Theoretical simulations show that multiple hotspots acting on different molecular sites are required to explain these multipeak features, suggesting that the source of long-duration blinking events is multiple atomic-scale protrusions interacting simultaneously with different sites of individual molecules or each with a different molecule. In this study, we investigate the intensity and spectral fluctuations in surface-enhanced Raman scattering (SERS) signals from individual plasmonic nanocavities. Extremely long-duration blinking components lasting up to minutes are observed in the SERS intensity fluctuation at room temperature, which can be characterized by successive and random appearance and eventual disappearance of multiple vibrational modes at different frequencies. Theoretical simulations show that multiple hotspots acting on different molecular sites are required to explain these multipeak features, suggesting that the source of long-duration blinking events is multiple atomic-scale protrusions interacting simultaneously with different sites of individual molecules or each with a different molecule.
Chinese Optics Letters
- Publication Date: Apr. 10, 2025
- Vol. 23, Issue 4, 043602 (2025)
Coherent coupling in a WS2/graphene van der Waals heterostructure integrated with an Au nanoantenna
Liping Hou, Qifa Wang, Huan Luo, Chenyang Li, Xuetao Gan, Fajun Xiao, and Jianlin Zhao
Coherent interactions between excitons strongly coupled to plasmons are vital for quantum information devices. For practical applications, suppressing the incoherent dissipation pathways in the hybrid system is essential. Here, we report on a strong plasmon–exciton coupling in a monolayer WS2/graphene van der Waals heterostructure (WS2/Gr vdWhs) integrated with an Au nanocube (Au NC). The presence of graphene effectively suppresses the nonradiative decay pathway of neutral excitons in the vdWhs, resulting in a narrower photoluminescence (PL) linewidth. The further integration of the WS2/Gr vdWhs with the Au NC enables coherent interaction between the in-plane exciton and a tilted plasmonic dipole, delivering a Rabi splitting energy of 120 meV and an incoherent coupling strength of 1 meV. Our findings possess the potential to facilitate the advancement of quantum nanophotonic devices. Coherent interactions between excitons strongly coupled to plasmons are vital for quantum information devices. For practical applications, suppressing the incoherent dissipation pathways in the hybrid system is essential. Here, we report on a strong plasmon–exciton coupling in a monolayer WS2/graphene van der Waals heterostructure (WS2/Gr vdWhs) integrated with an Au nanocube (Au NC). The presence of graphene effectively suppresses the nonradiative decay pathway of neutral excitons in the vdWhs, resulting in a narrower photoluminescence (PL) linewidth. The further integration of the WS2/Gr vdWhs with the Au NC enables coherent interaction between the in-plane exciton and a tilted plasmonic dipole, delivering a Rabi splitting energy of 120 meV and an incoherent coupling strength of 1 meV. Our findings possess the potential to facilitate the advancement of quantum nanophotonic devices.
Chinese Optics Letters
- Publication Date: Apr. 09, 2025
- Vol. 23, Issue 4, 043601 (2025)
Fabrication of sub-diffraction limit high-aspect-ratio nanostructures via laser direct writing|On the Cover
Guoliang Chen, Houan Teng, Jian Chen, and Qiwen Zhan
High-aspect-ratio structures with heights or depths significantly exceeding their lateral dimensions hold broad application potential across various fields. The production of these structures is challenging, requiring meticulous control over materials, scale, and precision. We introduce an economical and efficient approach for fabricating high-aspect-ratio nanostructures using a two-photon polymerization process. This approach achieves feature sizes of around 37 nm with an aspect ratio of 10:1 using commercial photoresists. Offering advantages over traditional techniques, our approach simplifies operation and enhances design flexibility, facilitating the creation of smaller, more complex, and high-aspect-ratio structures. The capabilities of this approach are demonstrated by producing arrays of three-dimensional microstructures that exhibit sub-micron scales, extensive periodicity, and pronounced aspect ratios. These developments open new possibilities for applications in biomedical, precision engineering, and optical microdevice manufacturing. High-aspect-ratio structures with heights or depths significantly exceeding their lateral dimensions hold broad application potential across various fields. The production of these structures is challenging, requiring meticulous control over materials, scale, and precision. We introduce an economical and efficient approach for fabricating high-aspect-ratio nanostructures using a two-photon polymerization process. This approach achieves feature sizes of around 37 nm with an aspect ratio of 10:1 using commercial photoresists. Offering advantages over traditional techniques, our approach simplifies operation and enhances design flexibility, facilitating the creation of smaller, more complex, and high-aspect-ratio structures. The capabilities of this approach are demonstrated by producing arrays of three-dimensional microstructures that exhibit sub-micron scales, extensive periodicity, and pronounced aspect ratios. These developments open new possibilities for applications in biomedical, precision engineering, and optical microdevice manufacturing.
Chinese Optics Letters
- Publication Date: Mar. 18, 2025
- Vol. 23, Issue 3, 033602 (2025)
Laser frequency stabilization with a metasurface chip through atomic spectral manipulation
Chen Qing, Lishuang Feng, and Dengke Zhang
Atomic spectroscopy serves as the basis for quantum precision measurements, where frequency-stabilized lasers are crucial for obtaining accurate atomic spectra. This work introduces a compact laser frequency stabilization system that employs a multifunctional metasurface to adjust the polarization, amplitude, and propagation direction of incident light. By combining with a Rb atomic vapor cell, the system achieves a tunable sub-Doppler spectrum for laser frequency stabilization. The experimental result demonstrates that a laser frequency stability of 3 × 10-11 is attained from 1 to 200 s at 780 nm with the input power at 20 µW. The devices hold significant potential for compactness, integration, and mass production, making them highly suitable for quantum measurement applications. Atomic spectroscopy serves as the basis for quantum precision measurements, where frequency-stabilized lasers are crucial for obtaining accurate atomic spectra. This work introduces a compact laser frequency stabilization system that employs a multifunctional metasurface to adjust the polarization, amplitude, and propagation direction of incident light. By combining with a Rb atomic vapor cell, the system achieves a tunable sub-Doppler spectrum for laser frequency stabilization. The experimental result demonstrates that a laser frequency stability of 3 × 10-11 is attained from 1 to 200 s at 780 nm with the input power at 20 µW. The devices hold significant potential for compactness, integration, and mass production, making them highly suitable for quantum measurement applications.
Chinese Optics Letters
- Publication Date: Mar. 12, 2025
- Vol. 23, Issue 3, 033601 (2025)
Exploring coupling flip mechanisms via plasmon-induced transparency in active metamaterials
Zhiqiang Wu, Jingxiang Gao, Qingxiu Yang, Jiahao Chi, Guifang Wang, Songlin Zhuang, and Qingqing Cheng
Comparing the coupling strength with both the mean and the product of the square roots of the respective damping rates for the bright and dark modes is a crucial metric in the study of plasmon-induced transparency (PIT). The flip in the ratio determines whether the coupling state between the structural units is strong or weak and also applies to the group delay. Our study explores two primary coupling channels within PIT structures: the inter-resonator distance (d) between the split-ring resonators (SRRs) and the cut wire (CW) and the spacing (g) between the SRRs. In the simulations, photosensitive silicon is embedded in the openings of the dark mode SRR resonator, actively modulating the dispersion characteristics and the coupling strength. Furthermore, we methodically examine the influence of these coupling channels on the transition between the coupling states, as well as on the maximal group delay in the PIT effect. Theoretically, leveraging the parameter fitting via the Lorentz coupling resonator model identifies the dominant parameters governing coupling state flips and differential regulation mechanisms. Our findings contribute to a deeper understanding of PIT phenomena and offer insights into optimizing PIT structures for diverse applications. Comparing the coupling strength with both the mean and the product of the square roots of the respective damping rates for the bright and dark modes is a crucial metric in the study of plasmon-induced transparency (PIT). The flip in the ratio determines whether the coupling state between the structural units is strong or weak and also applies to the group delay. Our study explores two primary coupling channels within PIT structures: the inter-resonator distance (d) between the split-ring resonators (SRRs) and the cut wire (CW) and the spacing (g) between the SRRs. In the simulations, photosensitive silicon is embedded in the openings of the dark mode SRR resonator, actively modulating the dispersion characteristics and the coupling strength. Furthermore, we methodically examine the influence of these coupling channels on the transition between the coupling states, as well as on the maximal group delay in the PIT effect. Theoretically, leveraging the parameter fitting via the Lorentz coupling resonator model identifies the dominant parameters governing coupling state flips and differential regulation mechanisms. Our findings contribute to a deeper understanding of PIT phenomena and offer insights into optimizing PIT structures for diverse applications.
Chinese Optics Letters
- Publication Date: Mar. 05, 2025
- Vol. 23, Issue 2, 023606 (2025)
Terahertz metalenses for needle beam generation through coherent polarization multiplexing
Shengnan Guan, Jierong Cheng, Haifeng Xu, Fan Li, and Shengjiang Chang
Lenses with desired depth of focus have crucial applications in imaging systems. However, there is little theoretical guidance to extend the depth of focus beyond numerical optimization. The on-demand construction of the Jones matrix using the composite metasurface brings a powerful tool for polarization-multiplexed functionalities. Here, based on polarization-multiplexed focusing in four linear polarization channels, we propose a straightforward method to extend the depth of focus based on the coherent superposition of each linear polarization channel. The metalens shows long and uniform needle beam focusing with a depth of focus of 46λ in circularly polarized excitation in the experiment, which offers a promising tool to tailor the terahertz focal spot for imaging applications. Lenses with desired depth of focus have crucial applications in imaging systems. However, there is little theoretical guidance to extend the depth of focus beyond numerical optimization. The on-demand construction of the Jones matrix using the composite metasurface brings a powerful tool for polarization-multiplexed functionalities. Here, based on polarization-multiplexed focusing in four linear polarization channels, we propose a straightforward method to extend the depth of focus based on the coherent superposition of each linear polarization channel. The metalens shows long and uniform needle beam focusing with a depth of focus of 46λ in circularly polarized excitation in the experiment, which offers a promising tool to tailor the terahertz focal spot for imaging applications.
Chinese Optics Letters
- Publication Date: Mar. 05, 2025
- Vol. 23, Issue 2, 023605 (2025)
Terahertz biosensor supported by quasi-bound states in the continuum for lung cancer cell sensing
Fan Yang, Shuocheng She, Jitao Li, Zhen Yue, Qianyun Zhang, Yating Zhang, Xin Ding, and Jianquan Yao
We design a terahertz (THz) biosensor supported by quasi-bound states in the continuum (QBICs) for lung cancer cell sensing. By destroying the in-plane symmetry of the bound state in the continuum (BIC), a QBIC with a high Q-factor is obtained. The designed biosensor exhibits excellent refractive index performance with a sensitivity of 354 GHZ/RIU. Unlike traditional detection schemes that require sample drying, a microfluidic liquid sample pool is utilized to detect different concentrations of lung cancer cells. As the cell concentration increases, the resonance frequency and intensity of the measured spectrum show significant changes. The designed sensor allows non-invasive real-time detection of living lung cancer cells, providing a potentially effective tool for early diagnosis and treatment of lung cancer. We design a terahertz (THz) biosensor supported by quasi-bound states in the continuum (QBICs) for lung cancer cell sensing. By destroying the in-plane symmetry of the bound state in the continuum (BIC), a QBIC with a high Q-factor is obtained. The designed biosensor exhibits excellent refractive index performance with a sensitivity of 354 GHZ/RIU. Unlike traditional detection schemes that require sample drying, a microfluidic liquid sample pool is utilized to detect different concentrations of lung cancer cells. As the cell concentration increases, the resonance frequency and intensity of the measured spectrum show significant changes. The designed sensor allows non-invasive real-time detection of living lung cancer cells, providing a potentially effective tool for early diagnosis and treatment of lung cancer.
Chinese Optics Letters
- Publication Date: Mar. 10, 2025
- Vol. 23, Issue 2, 023604 (2025)
An efficient design method of dual-polarized reconfigurable intelligent surface
Wanwan Cao, Junwei Zhang, Junyan Dai, Lijie Wu, Hanqing Yang, Zhen Zhang, Huidong Li, and Qiang Cheng
Dual-polarized reconfigurable intelligent surfaces (RISs) increasingly play significant roles in reshaping wireless transmission environments. In this Letter, we propose a design method for dual-polarized RIS elements. This proposed method develops an equivalent multiport model to quickly calculate reflection electromagnetic (EM) responses of the elements containing multiple structural parameters. Moreover, the genetic algorithm (GA) is utilized to optimize the structural parameters to meet design specifications. A 1-bit dual-polarized RIS is implemented for verification. The simulated and experimental results show good consistency with the calculated results. The proposed method significantly conserves design resources, promoting the development of dual-polarized RISs. Dual-polarized reconfigurable intelligent surfaces (RISs) increasingly play significant roles in reshaping wireless transmission environments. In this Letter, we propose a design method for dual-polarized RIS elements. This proposed method develops an equivalent multiport model to quickly calculate reflection electromagnetic (EM) responses of the elements containing multiple structural parameters. Moreover, the genetic algorithm (GA) is utilized to optimize the structural parameters to meet design specifications. A 1-bit dual-polarized RIS is implemented for verification. The simulated and experimental results show good consistency with the calculated results. The proposed method significantly conserves design resources, promoting the development of dual-polarized RISs.
Chinese Optics Letters
- Publication Date: Mar. 05, 2025
- Vol. 23, Issue 2, 023603 (2025)
Excitation of multiple bound states in the continuum by arbitrary selection of perturbation via a dielectric metasurface
Xin Luo, Shilin Yu, Yingli Ha, Fei Zhang, Mingbo Pu, Qiong He, Yinghui Guo, Mingfeng Xu, and Xiangang Luo
In this paper, a new strategy is proposed based on arbitrary selection of perturbation in a dielectric metasurface to achieve multiple quasi-bound states in the continuum (BICs) with identical modes under dual polarizations. Three distinct symmetry-broken perturbations are discussed. By selecting an arbitrary perturbation, triple quasi-BICs can be induced in transverse magnetic polarization modes at wavelengths of 1071.18, 1098.8, and 1199.6 nm, respectively. Simultaneously, double quasi-BICs at wavelengths of 1375.9 and 1628.5 nm are generated in transverse electric polarization modes. Moreover, the excited quasi-BICs exhibit excellent sensing performance with a maximum sensitivity of 900 nm/RIU, which is better than similar previous studies. In this paper, a new strategy is proposed based on arbitrary selection of perturbation in a dielectric metasurface to achieve multiple quasi-bound states in the continuum (BICs) with identical modes under dual polarizations. Three distinct symmetry-broken perturbations are discussed. By selecting an arbitrary perturbation, triple quasi-BICs can be induced in transverse magnetic polarization modes at wavelengths of 1071.18, 1098.8, and 1199.6 nm, respectively. Simultaneously, double quasi-BICs at wavelengths of 1375.9 and 1628.5 nm are generated in transverse electric polarization modes. Moreover, the excited quasi-BICs exhibit excellent sensing performance with a maximum sensitivity of 900 nm/RIU, which is better than similar previous studies.
Chinese Optics Letters
- Publication Date: Feb. 28, 2025
- Vol. 23, Issue 2, 023602 (2025)
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