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| 1 | All-optical active THz metasurfaces for ultrafast polarization switching and dynamic beam splitting显示文摘Miniaturized ultrafast switchable optical components with an extremely compact size and a high-speed response will be the core of next-generation all-optical devices instead of traditional integrated circuits,which are approaching the bottleneck of Moore’s Law.Metasurfaces have emerged as fascinating subwavelength flat optical components and devices for light focusing and holography applications.However,these devices exhibit a severe limitation due to their natural passive response.Here we introduce an active hybrid metasurface integrated with patterned semiconductor inclusions for all-optical active control of terahertz waves.Ultrafast modulation of polarization states and the beam splitting ratio are experimentally demonstrated on a time scale of 667 ps.This scheme of hybrid metasurfaces could also be extended to the design of various free-space all-optical active devices,such as varifocal planar lenses,switchable vector beam generators,and components for holography in ultrafast imaging,display,and high-fidelity terahertz wireless communication systems. | Longqing Cong Yogesh Kumar Srivastava Huifang Zhang Xueqian Zhang Jiaguang Han Ranjan Singh | 2018 | Light(Science & Applications)2018，7，1： | 15 |
| 2 | Electrically Programmable Terahertz Diatomic Metamolecules for Chiral Optical Control显示文摘Optical chirality is central to many industrial photonic technologies including enantiomer identifcation,ellipsometry-based tomography,and spin multiplexing in optical communications.However,a substantial chiral response requires a threedimensional constituent,thereby making the morphology highly complex to realize structural reconfguration.Moreover,an active reconfguration demands intense dosage of external stimuli that pose a major limitation for on-chip integration.Here,we report a low bias,electrically programmable synthetic chiral paradigm with a remarkable reconfguration among levorotatory,dextrorotatory,achiral,and racemic conformations.Te switchable optical activity induced by the chiral conformations enables a transmission-type duplex spatial light modulator for terahertz single pixel imaging.Te prototype delivers a new strategy towards reconfgurable stereoselective photonic applications and opens up avenues for on-chip programmable chiral devices with tremendous applications in biology,medicine,chemistry,and photonics. | Longqing Cong Prakash Pitchappa Nan Wang Ranjan Singh | 2019 | Research2019，，1： | 8 |
| 3 | Broadband terahertz rotator with an all-dielectric metasurface显示文摘Polarization manipulation is essential in developing cutting-edge photonic devices ranging from optical communication displays to solar energy harvesting. Most previous works for efficient polarization control cannot avoid utilizing metallic components that inevitably suffer from large ohmic loss and thus low operational efficiency.Replacing metallic components with Mie resonance-based dielectric resonators will largely suppress the ohmic loss toward high-efficiency metamaterial devices. Here, we propose an efficient approach for broadband, highquality polarization rotation operating in transmission mode with all-dielectric metamaterials in the terahertz regime. By separating the orthogonal polarization components in space, we obtain rotated output waves with a conversion efficiency of 67.5%. The proposed polarization manipulation strategy shows impressive robustness and flexibility in designing metadevices of both linear-and circular-polarization incidences. | QUANLONG YANG XIEYU CHEN QUAN XU CHUNXIU TIAN YUEHONG XU LONGQING CONG XUEQIAN ZHANG YANFENG LI CAIHONG ZHANG XIXIANG ZHANG JIAGUANG HAN WEILI ZHANG | 2018 | Photonics Research2018，，11： | 2 |
| 4 | Terahertz bound states in the continuum with incident angle robustness induced by a dual period metagrating显示文摘Metasurface-empowered bound state in the continuum(BIC)provides a unique route for fascinating functional devices with infinitely high quality factors.This method is particularly attractive to the terahertz community because it may essentially solve the deficiencies in terahertz filters,sensors,lasers,and nonlinear sources.However,most BIC metasurfaces are limited to specified incident angles that seriously dim their application prospects.Here,we propose that a dual-period dielectric metagrating can support multiple families of BICs that originate from guided mode resonances in the dielectric grating and exhibit infinite quality factors at arbitrarily tilted incidence.This robustness was analyzed based on the Bloch theory and verified at tilted incident angles.We also demonstrate that inducing geometric asymmetry is an efficient way to manipulate the leakage and coupling of these BICs,which can mimic the electromagnetically induced transparency(EIT)effect in our dual-period metagrating.In this demonstration,a slow-light effect with a measured group delay of 117 ps was achieved.The incidence-insensitive BICs proposed here may greatly extend the application scenarios of the BIC effect.The high Q factor and outstanding slow-light effect in the metagrating show exciting prospects in realizing high-performance filters,sensors,and modulators for prompting terahertz applications. | Wenqiao Shi Jianqiang Gu Xingyuan Zhang Quan Xu Jiaguang Han Quanlong Yang Longqing Cong Weili Zhang | 2022 | Photonics Research2022，10，3： | 1 |
| 5 | Hybrid bound states in the continuum in terahertz metasurfaces显示文摘Bound states in the continuum(BICs)have exhibited extraordinary properties in photonics for enhanced light-matter interactions that enable appealing applications in nonlinear optics,biosensors,and ultrafast optical switches.The most common strategy to apply BICs in a metasurface is by breaking symmetry of resonators in the uniform array that leaks the otherwise uncoupled mode to free space and exhibits an inverse quadratic relationship between quality factor(Q)and asymmetry.Here,we propose a scheme to further reduce scattering losses and improve the robustness of symmetry-protected BICs by decreasing the radiation density with a hybrid BIC lattice.We observe a significant increase of radiative Q in the hybrid lattice compared to the uniform lattice with a factor larger than 14.6.In the hybrid BIC lattice,modes are transferred toГpoint inherited from high symmetric X,Y,and M points in the Brillouin zone that reveal as multiple Fano resonances in the far field and would find applications in hyperspectral sensing.This work initiates a novel and generalized path toward reducing scattering losses and improving the robustness of BICs in terms of lattice engineering that would release the rigid requirements of fabrication accuracy and benefit applications of photonics and optoelectronic devices. | Junxing Fan Zuolong Li Zhanqiang Xue Hongyang Xing Dan Lu Guizhen Xu Jianqiang Gu Jiaguang Han Longqing Cong | 2023 | Opto-Electronic Science2023，2，4： | 1 |
| 6 | Manipulating polarization states of terahertz radiation using metamaterials显示文摘 | Longqing Cong Wei Cao Zhen Tian Jianqiang Gu Jiaguang Han Weili Zhang | 2012 | New Journal of Physics2012，，11： | 1 |
| 7 | Recent Advances and Perspective of Photonic Bound States in the Continuum显示文摘Recent advancements in photonic bound states in the continuum(BICs)have opened up exciting new possibilities for the design of optoelectronic devices with improved performance.In this perspective article,we provide an overview of recent progress in photonic BICs based on metamaterials and photonic crystals,focusing on both the underlying physics and their practical applications.The first part of this article introduces 2 different interpretations of BICs,based on far-field interference of multipoles and near-field analysis of topological charges.We then discuss recent research on manipulating the far-field radiation properties of BICs through engineering topological charges.The second part of the article summarizes recent developments in the applications of BICs,including chiral light and vortex beam generation,nonlinear optical frequency conversion,sensors,and nanolasers.Finally,we conclude with a discussion of the potential of photonic BICs to advance terahertz applications in areas such as generation and detection,modulation,sensing,and isolation.Webelieve that continued researchinthis area will lead to exciting new advancements in optoelectronics,particularly in the field of terahertz devices. | Guizhen Xu Hongyang Xing Zhanqiang Xue Dan Lu Jinying Fan Junxing Fan Perry Ping Shum Longqing Cong | 2023 | Ultrafast Science2023，3，5： | 0 |
| 8 | RSPSSL:A novel high-fidelity Raman spectral preprocessing scheme to enhance biomedical applications and chemical resolution visualization显示文摘Raman spectroscopy has tremendous potential for material analysis with its molecular fingerprinting capability in many branches of science and technology.It is also an emerging omics technique for metabolic profiling to shape precision medicine.However,precisely attributing vibration peaks coupled with specific environmental,instrumental,and specimen noise is problematic.Intelligent Raman spectral preprocessing to remove statistical bias noise and sample-related errors should provide a powerful tool for valuable information extraction.Here,we propose a novel Raman spectral preprocessing scheme based on self-supervised learning(RSPSSL)with high capacity and spectral fidelity.It can preprocess arbitrary Raman spectra without further training at a speed of~1900 spectra per second without human interference.The experimental data preprocessing trial demonstrated its excellent capacity and signal fidelity with an 88%reduction in root mean square error and a 60%reduction in infinite norm({L}_{{\infty}})compared to established techniques.With this advantage,it remarkably enhanced various biomedical applications with a 400%accuracy elevation(ΔAUC)in cancer diagnosis,an average 38%(few-shot)and 242%accuracy improvement in paraquat concentration prediction,and unsealed the chemical resolution of biomedical hyperspectral images,especially in the spectral fingerprint region.It precisely preprocessed various Raman spectra from different spectroscopy devices,laboratories,and diverse applications.This scheme will enable biomedical mechanism screening with the label-free volumetric molecular imaging tool on organism and disease metabolomics profiling with a scenario of high throughput,cross-device,various analyte complexity,and diverse applications. | Jiaqi Hu Gina Jinna Chen Chenlong Xue Pei Liang Yanqun Xiang Chuanlun Zhang Xiaokeng Chi Guoying Liu Yanfang Ye Dongyu Cui De Zhang Xiaojun yu Hong Dang Wen Zhang Junfan Chen Quan Tang Penglai Guo Ho-Pui Ho Yuchao Li Longqing Cong Perry Ping Shum | 2024 | Light(Science & Applications)2024，13，2： | 0 |
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