Browsing by Author "Liu, Mengkun"

Now showing 1 - 5 of 5
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    Active control of micrometer plasmon propagation in suspended graphene
    (Nature Publishing Group, 2022-03-18) Hu, Hai; Yu, Renwen; Teng, Hanchao; Hu, Debo; Chen, Na; Qu, Yunpeng; Yang, Xiaoxia; Chen, Xinzhong; McLeod, A. S.; Alonso-González, Pablo; Guo, Xiangdong; Li, Chi; Yao, Ziheng; Li, Zhenjun; Chen, Jianing; Sun, Zhipei; Liu, Mengkun; García de Abajo, F. Javier; Dai, Qing; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; National Center for Nanoscience and Technology Beijing; Barcelona Institute of Science and Technology; Stony Brook University; Columbia University; University of Oviedo; CAS - Institute of Physics
    Due to the two-dimensional character of graphene, the plasmons sustained by this material have been invariably studied in supported samples so far. The substrate provides stability for graphene but often causes undesired interactions (such as dielectric losses, phonon hybridization, and impurity scattering) that compromise the quality and limit the intrinsic flexibility of graphene plasmons. Here, we demonstrate the visualization of plasmons in suspended graphene at room temperature, exhibiting high-quality factor Q~33 and long propagation length > 3 μm. We introduce the graphene suspension height as an effective plasmonic tuning knob that enables in situ change of the dielectric environment and substantially modulates the plasmon wavelength, propagation length, and group velocity. Such active control of micrometer plasmon propagation facilitates near-unity-order modulation of nanoscale energy flow that serves as a plasmonic switch with an on-off ratio above 14. The suspended graphene plasmons possess long propagation length, high tunability, and controllable energy transmission simultaneously, opening up broad horizons for application in nano-photonic devices.
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    Doping-driven topological polaritons in graphene/α-MoO3 heterostructures
    (Nature Publishing Group, 2022-09) Hu, Hai; Chen, Na; Teng, Hanchao; Yu, Renwen; Qu, Yunpeng; Sun, Jianzhe; Xue, Mengfei; Hu, Debo; Wu, Bin; Li, Chi; Chen, Jianing; Liu, Mengkun; Sun, Zhipei; Liu, Yunqi; Li, Peining; Fan, Shanhui; García de Abajo, F. Javier; Dai, Qing; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; National Center for Nanoscience and Technology Beijing; Barcelona Institute of Science and Technology; Peking University; CAS - Institute of Physics; Stony Brook University; Huazhong University of Science and Technology; Stanford University
    Control over charge carrier density provides an efficient way to trigger phase transitions and modulate the optoelectronic properties of materials. This approach can also be used to induce topological transitions in the optical response of photonic systems. Here we report a topological transition in the isofrequency dispersion contours of hybrid polaritons supported by a two-dimensional heterostructure consisting of graphene and α-phase molybdenum trioxide. By chemically changing the doping level of graphene, we observed that the topology of polariton isofrequency surfaces transforms from open to closed shapes as a result of doping-dependent polariton hybridization. Moreover, when the substrate was changed, the dispersion contour became dominated by flat profiles at the topological transition, thus supporting tunable diffractionless polariton propagation and providing local control over the optical contour topology. We achieved subwavelength focusing of polaritons down to 4.8% of the free-space light wavelength by using a 1.5-μm-wide silica substrate as an in-plane lens. Our findings could lead to on-chip applications in nanoimaging, optical sensing and manipulation of energy transfer at the nanoscale.
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    Probing optical anisotropy of nanometer-thin van der waals microcrystals by near-field imaging
    (2017-12-01) Hu, Debo; Yang, Xiaoxia; Li, Chi; Liu, Ruina; Yao, Ziheng; Hu, Hai; Corder, Stephanie N.Gilbert; Chen, Jianing; Sun, Zhipei; Liu, Mengkun; Dai, Qing; Department of Electronics and Nanoengineering; Zhipei Sun Group; Chinese Academy of Sciences; Stony Brook University; CAS - Institute of Physics
    Most van der Waals crystals present highly anisotropic optical responses due to their strong in-plane covalent bonding and weak out-of-plane interactions. However, the determination of the polarization-dependent dielectric constants of van der Waals crystals remains a nontrivial task, since the size and dimension of the samples are often below or close to the diffraction limit of the probe light. In this work, we apply an optical nano-imaging technique to determine the anisotropic dielectric constants in representative van der Waals crystals. Through the study of both ordinary and extraordinary waveguide modes in real space, we are able to quantitatively determine the full dielectric tensors of nanometer-thin molybdenum disulfide and hexagonal boron nitride microcrystals, the most-promising van der Waals semiconductor and dielectric. Unlike traditional reflection-based methods, our measurements are reliable below the length scale of the free-space wavelength and reveal a universal route for characterizing low-dimensional crystals with high anisotropies.
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    Roadmap on Label-Free Super-Resolution Imaging
    (Wiley-VCH Verlag, 2023-12) Astratov, Vasily N.; Sahel, Yair Ben; Eldar, Yonina C.; Huang, Luzhe; Ozcan, Aydogan; Zheludev, Nikolay; Zhao, Junxiang; Burns, Zachary; Liu, Zhaowei; Narimanov, Evgenii; Goswami, Neha; Popescu, Gabriel; Pfitzner, Emanuel; Kukura, Philipp; Hsiao, Yi Teng; Hsieh, Chia Lung; Abbey, Brian; Diaspro, Alberto; LeGratiet, Aymeric; Bianchini, Paolo; Shaked, Natan T.; Simon, Bertrand; Verrier, Nicolas; Debailleul, Matthieu; Haeberlé, Olivier; Wang, Sheng; Liu, Mengkun; Bai, Yeran; Cheng, Ji Xin; Kariman, Behjat S.; Fujita, Katsumasa; Sinvani, Moshe; Zalevsky, Zeev; Li, Xiangping; Huang, Guan Jie; Chu, Shi Wei; Tzang, Omer; Hershkovitz, Dror; Cheshnovsky, Ori; Huttunen, Mikko J.; Stanciu, Stefan G.; Smolyaninova, Vera N.; Smolyaninov, Igor I.; Leonhardt, Ulf; Sahebdivan, Sahar; Wang, Zengbo; Luk'yanchuk, Boris; Wu, Limin; Maslov, Alexey V.; Jin, Boya; Simovski, Constantin R.; Perrin, Stephane; Montgomery, Paul; Lecler, Sylvain; Department of Electronics and Nanoengineering; Kostantin Simovski Group; University of North Carolina at Charlotte; Weizmann Institute of Science; University of California, Los Angeles; University of Southampton; University of California, San Diego; Purdue University; University of Illinois at Urbana-Champaign; University of Oxford; Academia Sinica - Institute of Atomic and Molecular Sciences; La Trobe University; Italian Institute of Technology; Tel Aviv University; Université de Bordeaux; Université de Haute-Alsace; Wuhan University; Stony Brook University; Boston University; Osaka University; Bar-Ilan University; Jinan University; National Taiwan University; Tampere University; University Politehnica of Bucharest; Towson University; University of Maryland, College Park; EMTensor GmbH; Bangor University; Lomonosov Moscow State University; Fudan University; Lobachevsky State University of Nizhni Novgorod; Université de Strasbourg
    Label-free super-resolution (LFSR) imaging relies on light-scattering processes in nanoscale objects without a need for fluorescent (FL) staining required in super-resolved FL microscopy. The objectives of this Roadmap are to present a comprehensive vision of the developments, the state-of-the-art in this field, and to discuss the resolution boundaries and hurdles that need to be overcome to break the classical diffraction limit of the label-free imaging. The scope of this Roadmap spans from the advanced interference detection techniques, where the diffraction-limited lateral resolution is combined with unsurpassed axial and temporal resolution, to techniques with true lateral super-resolution capability that are based on understanding resolution as an information science problem, on using novel structured illumination, near-field scanning, and nonlinear optics approaches, and on designing superlenses based on nanoplasmonics, metamaterials, transformation optics, and microsphere-assisted approaches. To this end, this Roadmap brings under the same umbrella researchers from the physics and biomedical optics communities in which such studies have often been developing separately. The ultimate intent of this paper is to create a vision for the current and future developments of LFSR imaging based on its physical mechanisms and to create a great opening for the series of articles in this field.
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    Tunable Planar Focusing Based on Hyperbolic Phonon Polaritons in alpha-MoO3
    (WILEY-V C H VERLAG GMBH, 2022-06-09) Qu, Yunpeng; Chen, Na; Teng, Hanchao; Hu, Hai; Sun, Jianzhe; Yu, Renwen; Hu, Debo; Xue, Mengfei; Li, Chi; Wu, Bin; Chen, Jianing; Sun, Zhipei; Liu, Mengkun; Liu, Yunqi; García de Abajo, F. Javier; Dai, Qing; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; National Center for Nanoscience and Technology Beijing; Peking University; Barcelona Institute of Science and Technology; University of Chinese Academy of Sciences; CAS - Institute of Physics; Stony Brook University
    Manipulation of the propagation and energy-transport characteristics of sub-wavelength infrared (IR) light fields is critical for the application of nanophotonic devices in photocatalysis, biosensing, and thermal management. In this context, metamaterials are useful composite materials, although traditional metal-based structures are constrained by their weak mid-IR response, while their associated capabilities for optical propagation and focusing are limited by the size of attainable artificial optical structures and the poor performance of the available active means of control. Herein, a tunable planar focusing device operating in the mid-IR region is reported by exploiting highly oriented in-plane hyperbolic phonon polaritons in alpha-MoO3. Specifically, an unprecedented change of effective focal length of polariton waves from 0.7 to 7.4 mu m is demonstrated by the following three different means of control: the dimension of the device, the employed light frequency, and engineering of phonon-plasmon hybridization. The high confinement characteristics of phonon polaritons in alpha-MoO3 permit the focal length and focal spot size to be reduced to 1/15 and 1/33 of the incident wavelength, respectively. In particular, the anisotropic phonon polaritons supported in alpha-MoO3 are combined with tunable surface-plasmon polaritons in graphene to realize in situ and dynamical control of the focusing performance, thus paving the way for phonon-polariton-based planar nanophotonic applications.