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Wang Z, Huang J, Liu W, Xiong C, Hu B. Automatically Aligned and Environment-Friendly Twisted Stacking Terahertz Chiral Metasurface with Giant Circular Dichroism for Rapid Biosensing. ACS APPLIED MATERIALS & INTERFACES 2024. [PMID: 38491983 DOI: 10.1021/acsami.3c18947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/18/2024]
Abstract
Chiral metasurfaces are capable of generating a huge superchiral field, which has great potential in optoelectronics and biosensing. However, the conventional fabrication process suffers greatly from time consumption, high cost, and difficult multilayer alignment, which hinder its commercial application. Herein, we propose a twisted stacking carbon-based terahertz (THz) chiral metasurface (TCM) based on laser-induced graphene (LIG) technology. By repeating a two-step process of sticking a polyimide film, followed by laser direct writing, the two layers of the TCM are aligned automatically in the fabrication. Laser manufacturing also brings such high processing speed that a TCM with a size of 15 × 15 mm can be prepared in 60 s. In addition, due to the greater dissipation of LIG than that of metals in the THz band, a giant circular dichroism (CD) of +99.5 to -99.6% is experimentally realized. The THz biosensing of bovine serum albumin enhanced by the proposed TCMs is then demonstrated. A wide sensing range (0.5-50 mg mL-1) and a good sensitivity [ΔCD: 2.09% (mg mL-1)-1, Δf: 0.0034 THz (mg mL-1)-1] are proved. This LIG-based TCM provides an environment-friendly platform for chiral research and has great application potential in rapid and low-cost commercial biosensing.
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Affiliation(s)
- Zongyuan Wang
- Beijing Engineering Research Center for Mixed Reality and Advanced Display, School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, China
| | - Jianzhou Huang
- Beijing Engineering Research Center for Mixed Reality and Advanced Display, School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, China
| | - Weiguang Liu
- Beijing Engineering Research Center for Mixed Reality and Advanced Display, School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, China
| | - Chenjie Xiong
- Beijing Engineering Research Center for Mixed Reality and Advanced Display, School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, China
| | - Bin Hu
- Beijing Engineering Research Center for Mixed Reality and Advanced Display, School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, China
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2
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Li H, Wang L, Zhang Y, Zheng G. Theoretical Study of Strong Coupling between Molecular Shells and Chiral Plasmons of Gold Nanoparticles Helices. J Phys Chem Lett 2024; 15:2550-2556. [PMID: 38416028 DOI: 10.1021/acs.jpclett.4c00019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Abstract
Chiral plasmonic nanostructures can produce strong chiral optical responses and have potential applications in photonics. Experimentally, metallic nanoparticle helices have been synthesized to achieve strong chiral responses. Strong coupling effects between the quantum emitters and the plasmon have attracted significant attention in the past decade and have been recently extended to the chiral plasmon of nanostructures. However, the strong coupling between molecules and metallic nanosphere helices has not been reported yet. In this article we study theoretically such an effect and examine the modulation of chiral and coupling effects by illumination light and molecular layer thickness. Our study may guide further experimental studies.
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Affiliation(s)
- Haoyu Li
- Department of Physics, University of Science and Technology Beijing, 100083 Beijing, China
| | - Luxia Wang
- Department of Physics, University of Science and Technology Beijing, 100083 Beijing, China
| | - Yuan Zhang
- Henan Key Laboratory of Diamond Optoelectronic Materials and Devices, Key Laboratory of Material Physics Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Daxue Road 75, Zhengzhou 450052, China
- Institute of Quantum Materials and Physics, Henan Academy of Sciences, Zhengzhou 450046, China
| | - Guangchao Zheng
- Henan Key Laboratory of Diamond Optoelectronic Materials and Devices, Key Laboratory of Material Physics Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Daxue Road 75, Zhengzhou 450052, China
- Institute of Quantum Materials and Physics, Henan Academy of Sciences, Zhengzhou 450046, China
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Dai C, Wan S, Li Z, Shi Y, Zhang S, Li Z. Switchable unidirectional emissions from hydrogel gratings with integrated carbon quantum dots. Nat Commun 2024; 15:845. [PMID: 38287059 PMCID: PMC10825124 DOI: 10.1038/s41467-024-45284-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 01/19/2024] [Indexed: 01/31/2024] Open
Abstract
Directional emission of photoluminescence despite its incoherence is an attractive technique for light-emitting fields and nanophotonics. Optical metasurfaces provide a promising route for wavefront engineering at the subwavelength scale, enabling the feasibility of unidirectional emission. However, current directional emission strategies are mostly based on static metasurfaces, and it remains a challenge to achieve unidirectional emissions tuning with high performance. Here, we demonstrate quantum dots-hydrogel integrated gratings for actively switchable unidirectional emission with simultaneously a narrow divergence angle less than 1.5° and a large diffraction angle greater than 45°. We further demonstrate that the grating efficiency alteration leads to a more than 7-fold tuning of emission intensity at diffraction order due to the variation of hydrogel morphology subject to change in ambient humidity. Our proposed switchable emission strategy can promote technologies of active light-emitting devices for radiation control and optical imaging.
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Affiliation(s)
- Chenjie Dai
- Electronic Information School, Wuhan University, Wuhan, 430072, China
| | - Shuai Wan
- Electronic Information School, Wuhan University, Wuhan, 430072, China
| | - Zhe Li
- Electronic Information School, Wuhan University, Wuhan, 430072, China
| | - Yangyang Shi
- Electronic Information School, Wuhan University, Wuhan, 430072, China
| | - Shuang Zhang
- Department of Physics, The University of Hong Kong, Hong Kong, 999077, China.
| | - Zhongyang Li
- Electronic Information School, Wuhan University, Wuhan, 430072, China.
- Wuhan Institute of Quantum Technology, Wuhan, 430206, China.
- School of Microelectronics, Wuhan University, Wuhan, 430072, China.
- Suzhou Institute of Wuhan University, Suzhou, 215123, China.
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Wang F, Wang X, Lu X, Huang C. Nanophotonic Enhanced Chiral Sensing and Its Biomedical Applications. BIOSENSORS 2024; 14:39. [PMID: 38248416 PMCID: PMC11154488 DOI: 10.3390/bios14010039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 01/03/2024] [Accepted: 01/10/2024] [Indexed: 01/23/2024]
Abstract
Chiral sensing is crucial in the fields of biology and the pharmaceutical industry. Many naturally occurring biomolecules, i.e., amino acids, sugars, and nucleotides, are inherently chiral. Their enantiomers are strongly associated with the pharmacological effects of chiral drugs. Owing to the extremely weak chiral light-matter interactions, chiral sensing at an optical frequency is challenging, especially when trace amounts of molecules are involved. The nanophotonic platform allows for a stronger interaction between the chiral molecules and light to enhance chiral sensing. Here, we review the recent progress in nanophotonic-enhanced chiral sensing, with a focus on the superchiral near-field and enhanced circular dichroism (CD) spectroscopy generated in both the dielectric and in plasmonic structures. In addition, the recent applications of chiral sensing in biomedical fields are discussed, including the detection and treatment of difficult diseases, i.e., Alzheimer's disease, diabetes, and cancer.
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Affiliation(s)
- Fei Wang
- Institute of Microelectronics of the Chinese Academy of Sciences, Beijing 100029, China;
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xue Wang
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China;
| | - Xinchao Lu
- Institute of Microelectronics of the Chinese Academy of Sciences, Beijing 100029, China;
| | - Chengjun Huang
- Institute of Microelectronics of the Chinese Academy of Sciences, Beijing 100029, China;
- University of Chinese Academy of Sciences, Beijing 100049, China
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Han D, Ye T, Wei Y. Spatial modulation of scalable nanostructures by combining maskless plasmonic lithography and grayscale-patterned strategy. NANOSCALE ADVANCES 2023; 5:4424-4434. [PMID: 37638165 PMCID: PMC10448319 DOI: 10.1039/d3na00147d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 06/23/2023] [Indexed: 08/29/2023]
Abstract
Nanolithography techniques providing good scalability and feature size controllability are of great importance for the fabrication of integrated circuits (IC), MEMS/NEMS, optical devices, nanophotonics, etc. Herein, a cost-effective, easy access, and high-fidelity patterning strategy that combines the high-resolution capability of maskless plasmonic lithography with the spatial morphology controllability of grayscale lithography is proposed to generate the customized pattern profile from microscale to nanoscale. Notably, the scaling effect of gap size in plasmonic lithography with a contact bowtie-shaped nanoaperture (BNA) is found to be essential to the rapid decay characteristics of an evanescent field, which leads to a wide energy bandwidth of the required optimal dose to record pattern in per unit volume, and hence, achieves the volumetrically scalable control of the photon energy deposition in the space more precisely. Based on the proper calibration and cooperation of pattern width and depth, a grayscale-patterned map is designed to compensate for the dose difference caused by the loss of the high spatial frequency component of the evanescent field. A Lena nanostructure with varying feature sizes by spatially modulating the exposure dose distribution was successfully demonstrated, and besides, we also successfully generated a microlens array (MLA) with high uniformity. The practical patterning method makes plasmonic lithography significant in the fabrication of functional nanostructures with high performance, including metasurfaces, plasmonics, and optical imaging systems.
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Affiliation(s)
- Dandan Han
- University of Chinese Academy of Sciences, School of Integrated Circuits Beijing 100049 China
| | - Tianchun Ye
- University of Chinese Academy of Sciences, School of Integrated Circuits Beijing 100049 China
- Chinese Academy of Sciences, Institute of Microelectronics Beijing 100029 China
| | - Yayi Wei
- University of Chinese Academy of Sciences, School of Integrated Circuits Beijing 100049 China
- Chinese Academy of Sciences, Institute of Microelectronics Beijing 100029 China
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Li D, Xu C, Xie J, Lee C. Research Progress in Surface-Enhanced Infrared Absorption Spectroscopy: From Performance Optimization, Sensing Applications, to System Integration. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2377. [PMID: 37630962 PMCID: PMC10458771 DOI: 10.3390/nano13162377] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 08/13/2023] [Accepted: 08/17/2023] [Indexed: 08/27/2023]
Abstract
Infrared absorption spectroscopy is an effective tool for the detection and identification of molecules. However, its application is limited by the low infrared absorption cross-section of the molecule, resulting in low sensitivity and a poor signal-to-noise ratio. Surface-Enhanced Infrared Absorption (SEIRA) spectroscopy is a breakthrough technique that exploits the field-enhancing properties of periodic nanostructures to amplify the vibrational signals of trace molecules. The fascinating properties of SEIRA technology have aroused great interest, driving diverse sensing applications. In this review, we first discuss three ways for SEIRA performance optimization, including material selection, sensitivity enhancement, and bandwidth improvement. Subsequently, we discuss the potential applications of SEIRA technology in fields such as biomedicine and environmental monitoring. In recent years, we have ushered in a new era characterized by the Internet of Things, sensor networks, and wearable devices. These new demands spurred the pursuit of miniaturized and consolidated infrared spectroscopy systems and chips. In addition, the rise of machine learning has injected new vitality into SEIRA, bringing smart device design and data analysis to the foreground. The final section of this review explores the anticipated trajectory that SEIRA technology might take, highlighting future trends and possibilities.
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Affiliation(s)
- Dongxiao Li
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore; (D.L.); (C.X.); (J.X.)
- Center for Intelligent Sensors and MEMS (CISM), National University of Singapore, Singapore 117608, Singapore
| | - Cheng Xu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore; (D.L.); (C.X.); (J.X.)
- Center for Intelligent Sensors and MEMS (CISM), National University of Singapore, Singapore 117608, Singapore
| | - Junsheng Xie
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore; (D.L.); (C.X.); (J.X.)
- Center for Intelligent Sensors and MEMS (CISM), National University of Singapore, Singapore 117608, Singapore
| | - Chengkuo Lee
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore; (D.L.); (C.X.); (J.X.)
- Center for Intelligent Sensors and MEMS (CISM), National University of Singapore, Singapore 117608, Singapore
- NUS Suzhou Research Institute (NUSRI), Suzhou 215123, China
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Ou K, Wan H, Wang G, Zhu J, Dong S, He T, Yang H, Wei Z, Wang Z, Cheng X. Advances in Meta-Optics and Metasurfaces: Fundamentals and Applications. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:1235. [PMID: 37049327 PMCID: PMC10097126 DOI: 10.3390/nano13071235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 03/20/2023] [Accepted: 03/23/2023] [Indexed: 06/19/2023]
Abstract
Meta-optics based on metasurfaces that interact strongly with light has been an active area of research in recent years. The development of meta-optics has always been driven by human's pursuits of the ultimate miniaturization of optical elements, on-demand design and control of light beams, and processing hidden modalities of light. Underpinned by meta-optical physics, meta-optical devices have produced potentially disruptive applications in light manipulation and ultra-light optics. Among them, optical metalens are most fundamental and prominent meta-devices, owing to their powerful abilities in advanced imaging and image processing, and their novel functionalities in light manipulation. This review focuses on recent advances in the fundamentals and applications of the field defined by excavating new optical physics and breaking the limitations of light manipulation. In addition, we have deeply explored the metalenses and metalens-based devices with novel functionalities, and their applications in computational imaging and image processing. We also provide an outlook on this active field in the end.
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Affiliation(s)
- Kai Ou
- Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
- MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai 200092, China
- Shanghai Frontiers Science Center of Digital Optics, Shanghai 200092, China
| | - Hengyi Wan
- Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
- MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai 200092, China
- Shanghai Frontiers Science Center of Digital Optics, Shanghai 200092, China
| | - Guangfeng Wang
- Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Jingyuan Zhu
- Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
- MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai 200092, China
- Shanghai Frontiers Science Center of Digital Optics, Shanghai 200092, China
| | - Siyu Dong
- Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
- MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai 200092, China
- Shanghai Frontiers Science Center of Digital Optics, Shanghai 200092, China
| | - Tao He
- Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
- MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai 200092, China
- Shanghai Frontiers Science Center of Digital Optics, Shanghai 200092, China
| | - Hui Yang
- National Research Center for High-Efficiency Grinding, College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, China
| | - Zeyong Wei
- Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
- MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai 200092, China
- Shanghai Frontiers Science Center of Digital Optics, Shanghai 200092, China
| | - Zhanshan Wang
- Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
- MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai 200092, China
- Shanghai Frontiers Science Center of Digital Optics, Shanghai 200092, China
- Shanghai Institute of Intelligent Science and Technology, Tongji University, Shanghai 200092, China
| | - Xinbin Cheng
- Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
- MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai 200092, China
- Shanghai Frontiers Science Center of Digital Optics, Shanghai 200092, China
- Shanghai Institute of Intelligent Science and Technology, Tongji University, Shanghai 200092, China
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Han Z, Wang F, Sun J, Wang X, Tang Z. Recent Advances in Ultrathin Chiral Metasurfaces by Twisted Stacking. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2206141. [PMID: 36284479 DOI: 10.1002/adma.202206141] [Citation(s) in RCA: 20] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 09/22/2022] [Indexed: 06/16/2023]
Abstract
Artificial chiral nanostructures have been subjected to extensive research for their unique chiroptical activities. Planarized chiral films of ultrathin thicknesses are in particular demand for easy on-chip integration and improved energy efficiency as polarization-sensitive metadevices. Recently, controlled twisted stacking of two or more layers of nanomaterials, such as 2D van der Waals materials, ultrathin films, or traditional metasurfaces, at an angle has emerged as a general strategy to introduce optical chirality into achiral solid-state systems. This method endows new degrees of freedom, e.g., the interlayer twist angle, to flexibly engineer and tune the chiroptical responses without having to change the material or the design, thus greatly facilitating the development of multifunctional metamaterials. In this review, recent exciting progress in planar chiral metasurfaces are summarized and discussed from the viewpoints of building blocks, fabrication methods, as well as circular dichroism and modulation thereof in twisted stacked nanostructures. The review further highlights the ever-growing portfolio of applications of these chiral metasurfaces, including polarization conversion, information encryption, chiral sensing, and as an engineering platform for hybrid metadevices. Finally, forward-looking prospects are provided.
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Affiliation(s)
- Zexiang Han
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
| | - Fei Wang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
| | - Juehan Sun
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
| | - Xiaoli Wang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
| | - Zhiyong Tang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China
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He H, Cen M, Wang J, Xu Y, Liu J, Cai W, Kong D, Li K, Luo D, Cao T, Liu YJ. Plasmonic Chiral Metasurface-Induced Upconverted Circularly Polarized Luminescence from Achiral Upconversion Nanoparticles. ACS APPLIED MATERIALS & INTERFACES 2022; 14:53981-53989. [PMID: 36378812 DOI: 10.1021/acsami.2c13267] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Chirality induction, transfer, and manipulation have aroused great interest in achiral nanomaterials. Here, we demonstrate strong upconverted circularly polarized luminescence from achiral core-shell upconversion nanoparticles (UCNPs) via a plasmonic chiral metasurface-induced optical chirality transfer. The Yb3+-sensitized core-shell UCNPs with good dispersity exhibit intense upconversion luminescence of Tm3+ and Nd3+ through the energy transfer process. By spin-coating the core-shell UCNPs on this chiral metasurface, strong enhancement and circular polarization modulation of upconversion luminescence can be achieved due to resonant coupling between surface plasmons and upconversion nanoparticles. In the UCNPs-on-metasurface composite, a significant upconversion luminescence enhancement can be achieved with a maximum enhancement factor of 32.63 at 878 nm and an overall enhancement factor of 11.61. The luminescence dissymmetry factor of the induced upconverted circularly polarized luminescence can reach 0.95 at the emission wavelength of 895 nm. The UCNPs-on-metasurface composite yields efficient modulation for the emission intensity and polarization of UCNPs, paving new pathways to many potential applications in imaging, sensing, and anticounterfeiting fields.
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Affiliation(s)
- Huilin He
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China
- Harbin Institute of Technology, Harbin 150001, China
| | - Mengjia Cen
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China
- Dalian University of Technology, Dalian 116024, China
| | - Jiawei Wang
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yiwei Xu
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Jianxun Liu
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Wenfeng Cai
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Delai Kong
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Ke Li
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Dan Luo
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Tun Cao
- Dalian University of Technology, Dalian 116024, China
| | - Yan Jun Liu
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China
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