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Ding G, Zhou Y, Zhang S, Luo X, Wang S. Design of a Reconfigurable Ultra-Wideband Terahertz Polarization Rotator Based on Graphene Metamaterial. SENSORS (BASEL, SWITZERLAND) 2023; 23:5449. [PMID: 37420616 DOI: 10.3390/s23125449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 06/06/2023] [Accepted: 06/07/2023] [Indexed: 07/09/2023]
Abstract
In this work, a reconfigurable ultra-wideband transmissive terahertz polarization rotator based on graphene metamaterial is proposed that can switch between two states of polarization rotation within a broad terahertz band by changing the Fermi level of graphene. The proposed reconfigurable polarization rotator is based on a two-dimensional periodic array of multilayer graphene metamaterial structure, which is composed of metal grating, graphene grating, silicon dioxide thin film, and a dielectric substrate. The graphene metamaterial can achieve high co-polarized transmission of a linearly polarized incident wave at the off-state of the graphene grating without applying the bias voltage. Once the specially designed bias voltage is applied to change the Fermi level of graphene, the polarization rotation angle of linearly polarized waves is switched to 45° by the graphene metamaterial at the on-state. The working frequency band with 45-degree linear polarized transmission remaining above 0.7 and the polarization conversion ratio (PCR) above 90% is from 0.35 to 1.75 THz, and the relative bandwidth reaches 133.3% of the central working frequency. Furthermore, even with oblique incidence at large angles, the proposed device retains high-efficiency conversion in a broad band. The proposed graphene metamaterial offers a novel approach for the design of a terahertz tunable polarization rotator and is expected to be applied in the applications of terahertz wireless communication, imaging, and sensing.
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Affiliation(s)
- Guowen Ding
- Research Center of Applied Electromagnetics, Nanjing University of Information Science and Technology, Nanjing 210044, China
- School of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China
| | - Yanjun Zhou
- Research Center of Applied Electromagnetics, Nanjing University of Information Science and Technology, Nanjing 210044, China
| | - Shuyang Zhang
- Research Center of Applied Electromagnetics, Nanjing University of Information Science and Technology, Nanjing 210044, China
| | - Xinyao Luo
- Research Center of Applied Electromagnetics, Nanjing University of Information Science and Technology, Nanjing 210044, China
- School of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China
| | - Shenyun Wang
- Research Center of Applied Electromagnetics, Nanjing University of Information Science and Technology, Nanjing 210044, China
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2
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Zhang R, Wang W. Perfect optical absorption in a single array of folded graphene ribbons. OPTICS EXPRESS 2022; 30:44726-44740. [PMID: 36522891 DOI: 10.1364/oe.473747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 11/02/2022] [Indexed: 06/17/2023]
Abstract
Due to its one atom thickness, optical absorption (OA) in graphene is a fundamental and challenging issue. Practically, the patterned graphene-dielectric-metal structure is commonly used to achieve perfect OA (POA). In this work, we propose a novel scenario to solve this issue, in which POA is obtained by using free-standing folded graphene ribbons (FGRs). We show several local resonances, e.g. a dipole state (Mode-I) and a bound state in continuum (BIC, Mode-II), will cause very efficient OA. At normal incidence, by choosing appropriate folding angle θ, 50% absorptance by the two states is easily achieved; at oblique incidence, the two states will result in roughly 98% absorptance as incidence angle φ≈40∘. It is also interesting to see that the system has asymmetric OA spectra, e.g. POA of the former (latter) state existing in reverse (forward) incidence, respectively. Besides the angles θ and φ, POA here can also be actively tuned by electrostatic gating. As increasing Fermi level, POA of Mode-I will undergo a gradual blueshift, while that of Mode-II will experience a rapid blueshift and then be divided into three branches, due to Fano coupling to two guided modes. In reality, the achieved POA is well maintained even the dielectric substrates are used to support FGRs. Our work offers a remarkable scenario to achieve POA, and thus enhance light-matter interaction in graphene, which can build an alternative platform to study novel optical effects in general two-dimensional (2D) materials. The folding, mechanical operation in out-of-plane direction, may emerge as a new degree of freedom for optoelectronic device applications based on 2D materials.
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3
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Bonatti L, Nicoli L, Giovannini T, Cappelli C. In silico design of graphene plasmonic hot-spots. NANOSCALE ADVANCES 2022; 4:2294-2302. [PMID: 35706845 PMCID: PMC9113057 DOI: 10.1039/d2na00088a] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 04/15/2022] [Indexed: 05/27/2023]
Abstract
We propose a route for the rational design of engineered graphene-based nanostructures, which feature enormously enhanced electric fields in their proximity. Geometrical arrangements are inspired by nanopatterns allowing single molecule detection on noble metal substrates, and are conceived to take into account experimental feasibility and ease in fabrication processes. The attention is especially focused on enhancement effects occurring close to edge defects and grain boundaries, which are usually present in graphene samples. There, very localized hot-spots are created, with enhancement factors comparable to noble metal substrates, thus potentially paving the way for single molecule detection from graphene-based substrates.
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Affiliation(s)
- Luca Bonatti
- Scuola Normale Superiore Piazza dei Cavalieri 7 56126 Pisa Italy
| | - Luca Nicoli
- Scuola Normale Superiore Piazza dei Cavalieri 7 56126 Pisa Italy
| | | | - Chiara Cappelli
- Scuola Normale Superiore Piazza dei Cavalieri 7 56126 Pisa Italy
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4
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A Parabola-like Gold Nanobowtie on a Sapphire Substrate as a Nano-Cavity. PHOTONICS 2022. [DOI: 10.3390/photonics9030193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Plasmonic, metallic nanostructures have attracted much interest for their ability to manipulate light on a subwavelength scale and for their related applications in various fields. In this work, a parabola-like gold nanobowtie (PGNB) on a sapphire substrate was designed as a nano-cavity for confining light waves in a nanoscale gap region. The near-field optical properties of the innovative PGNB structure were studied comprehensively, taking advantage of the time-resolved field calculation based on a finite-difference time-domain algorithm (FDTD). The calculation result showed that the resonance wavelength of the nano-cavity was quite sensitive to the geometry of the PGNB. The values that related to the scattering and absorption properties of the PGNB, such as the scattering cross section, absorption cross section, extinction cross section, scattering ratio, and also the absorption ratio, were strongly dependent on the geometrical parameters which affected the surface area of the nanobowtie. Increased sharpness of the gold tips on the parabola-like nano-wings benefited the concentration of high-density charges with opposite electric properties in the narrow gold tips with limited volume, thus, resulting in a highly enhanced electric field in the nano-cavity under illumination of the light wave. Reduction of the gap size between the two gold nano-tips, namely, the size of the nano-cavity, decreased the distance that the electric potential produced by the highly concentrated charges on the surface of each gold nano-tip had to jump across, therefore, causing a significantly enhanced field in the nano-cavity. Further, alignment of the linearly polarized electric field of the incident light wave with the symmetric axis of the PGNB efficiently enabled the free electrons in the PGNB to concentrate on the surface of the sharp gold tips with a high density, thus, strongly improving the field across the nano-cavity. The research provides a new insight for future design, nanofabrication, and characterization of PGNBs for applications in devices that relate to enhancing photons emission, improving efficiency for energy harvesting, and improving sensitivity for infrared detection.
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5
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Zhang R, You B, Wang S, Han K, Shen X, Wang W. Broadband and switchable terahertz polarization converter based on graphene metasurfaces. OPTICS EXPRESS 2021; 29:24804-24815. [PMID: 34614828 DOI: 10.1364/oe.432601] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 07/12/2021] [Indexed: 06/13/2023]
Abstract
In this work, we propose broadband and switchable terahertz (THz) polarization converters based on either graphene patch metasurface (GPMS) or its complementary structure (graphene hole metasurface, GHMS). The patch and hole are simply cross-shaped, composed of two orthogonal arms, along which plasmonic resonances mediated by Fabry-Perot cavity play a key role in polarization conversion (PC). An incidence of linear polarization will be converted to its cross-polarization (LTL) or circular polarization (LTC), as the reflected wave in the direction of two arms owning the same amplitude and π phase difference (LTL), or ±π/2 phase difference (LTC). Such requirements can be met by optimizing the width and length of two arms, thickness of dielectric layer, and Fermi level EF of graphene. By using GPMS, LTL PC of polarization conversion ratio (PCR) over 90% is achieved in the frequency range of 2.92 THz to 6.26 THz, and by using GHMS, LTC PC of ellipticity χ ≤ -0.9 at the frequencies from 4.45 THz to 6.47 THz. By varying the Fermi level, the operating frequency can be actively tuned, and the functionality can be switched without structural modulation; for instance, GPMS supports LTL PC as EF = 0.6 eV and LTC PC of χ ≥ 0.9 as EF = 1.0 eV, in the frequency range of 2.69 THz to 4.19 THz. Moreover, GHMS can be optimized to sustain LTL PC and LTC PC of |χ| ≥ 0.9, in the frequency range of 4.96 THz to 6.52 THz, which indicates that the handedness of circular polarization can be further specified. The proposed polarization converters of broad bandwidth, active tunability, and switchable functionality will essentially make a significant progress in THz technology and device applications, and can be widely utilized in THz communications, sensing and spectroscopy.
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Müller MM, Kosik M, Pelc M, Bryant GW, Ayuela A, Rockstuhl C, Słowik K. From single-particle-like to interaction-mediated plasmonic resonances in graphene nanoantennas. JOURNAL OF APPLIED PHYSICS 2021; 129:10.1063/5.0038883. [PMID: 36575704 PMCID: PMC9791988 DOI: 10.1063/5.0038883] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 02/12/2021] [Indexed: 06/17/2023]
Abstract
Plasmonic nanostructures attract tremendous attention as they confine electromagnetic fields well below the diffraction limit while simultaneously sustaining extreme local field enhancements. To fully exploit these properties, the identification and classification of resonances in such nanostructures is crucial. Recently, a novel figure of merit for resonance classification has been proposed1 and its applicability was demonstrated mostly to toy model systems. This novel measure, the energy-based plasmonicity index (EPI), characterizes the nature of resonances in molecular nanostructures. The EPI distinguishes between either a single-particle-like or a plasmonic nature of resonances based on the energy space coherence dynamics of the excitation. To advance the further development of this newly established measure, we present here its exemplary application to characterize the resonances of graphene nanoantennas. In particular, we focus on resonances in a doped nanoantenna. The structure is of interest, as a consideration of the electron dynamics in real space might suggest a plasmonic nature of selected resonances in the low doping limit but our analysis reveals the opposite. We find that in the undoped and moderately doped nanoantenna, the EPI classifies all emerging resonances as predominantly single-particle-like and only after doping the structure heavily, the EPI observes plasmonic response.
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Affiliation(s)
- Marvin M. Müller
- Institute of Theoretical Solid State Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
| | - Miriam Kosik
- Institute of Physics, Nicolaus Copernicus University in Toruń, Grudziadzka 5, 87-100 Toruń, Poland
| | - Marta Pelc
- Institute of Physics, Nicolaus Copernicus University in Toruń, Grudziadzka 5, 87-100 Toruń, Poland
- Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, 20018 Donostia-San Sebastián, Spain
- Centro de Física de Materiales, CFM-MPC CSIC-UPV/EHU, Paseo Manuel Lardizabal 5, 20018 Donostia-San Sebastián, Spain
| | - Garnett W. Bryant
- Joint Quantum Institute, University of Maryland and National Institute of Standards and Technology, College Park, Maryland 20742, USA
- Nanoscale Device Characterization Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Andrés Ayuela
- Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, 20018 Donostia-San Sebastián, Spain
- Centro de Física de Materiales, CFM-MPC CSIC-UPV/EHU, Paseo Manuel Lardizabal 5, 20018 Donostia-San Sebastián, Spain
| | - Carsten Rockstuhl
- Institute of Theoretical Solid State Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), 76021 Karlsruhe, Germany
| | - Karolina Słowik
- Institute of Physics, Nicolaus Copernicus University in Toruń, Grudziadzka 5, 87-100 Toruń, Poland
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7
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Brey L, Stauber T, Martín-Moreno L, Gómez-Santos G. Nonlocal Quantum Effects in Plasmons of Graphene Superlattices. PHYSICAL REVIEW LETTERS 2020; 124:257401. [PMID: 32639766 DOI: 10.1103/physrevlett.124.257401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 06/04/2020] [Indexed: 06/11/2023]
Abstract
By using a nonlocal, quantum mechanical response function we study graphene plasmons in a one-dimensional superlattice (SL) potential V_{0}cosG_{0}x. The SL introduces a quantum energy scale E_{G}∼ℏv_{F}G_{0} associated with electronic subband transitions. At energies lower than E_{G}, the plasmon dispersion is highly anisotropic; plasmons propagate perpendicularly to the SL axis, but become damped by electronic transitions along the SL direction. These results question the validity of semiclassical approximations for describing low energy plasmons in periodic structures. At higher energies, the dispersion becomes isotropic and Drude-like with effective Drude weights related to the average of the absolute value of the local chemical potential. Full quantum mechanical treatment of the kinetic energy thus introduces nonlocal effects that delocalize the plasmons in the SL, making the system behave as a metamaterial even near singular points where the charge density vanishes.
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Affiliation(s)
- Luis Brey
- Materials Science Factory, Instituto de Ciencia de Materiales de Madrid (CSIC), Cantoblanco, 28049 Madrid, Spain
| | - T Stauber
- Materials Science Factory, Instituto de Ciencia de Materiales de Madrid (CSIC), Cantoblanco, 28049 Madrid, Spain
| | - L Martín-Moreno
- Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, CSIC-Universidad de Zaragoza, E-50009 Zaragoza, Spain
| | - G Gómez-Santos
- Departamento de Física de la Materia Condensada, Instituto Nicolás Cabrera and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
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8
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Gil-Villalba A, Meyer R, Giust R, Rapp L, Billet C, Courvoisier F. Single shot femtosecond laser nano-ablation of CVD monolayer graphene. Sci Rep 2018; 8:14601. [PMID: 30279433 PMCID: PMC6168448 DOI: 10.1038/s41598-018-32957-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 09/19/2018] [Indexed: 11/28/2022] Open
Abstract
We investigate ablation of CVD monolayer graphene by femtosecond pulses in the single shot regime. We show that the ablation probability of flat graphene drastically reduces for small illumination diameters even if the ablation threshold is exceeded. However, the presence of graphene wrinkles enhances the ablation probability. This is interpreted in terms of electron and energy diffusion within the graphene layer. This differentiated behavior is a drawback for single shot laser nanopatterning. The morphology of the holes with minimal diameter depends on the fluence distribution at ablation threshold. Strong fluence gradients due to strong focussing produce an explosive folding of graphene during ablation.
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Affiliation(s)
- A Gil-Villalba
- FEMTO-ST institute, Univ. Bourgogne Franche-Comté, CNRS, 15B avenue des Montboucons, 25030, Besançon Cedex, France
| | - R Meyer
- FEMTO-ST institute, Univ. Bourgogne Franche-Comté, CNRS, 15B avenue des Montboucons, 25030, Besançon Cedex, France
| | - R Giust
- FEMTO-ST institute, Univ. Bourgogne Franche-Comté, CNRS, 15B avenue des Montboucons, 25030, Besançon Cedex, France
| | - L Rapp
- FEMTO-ST institute, Univ. Bourgogne Franche-Comté, CNRS, 15B avenue des Montboucons, 25030, Besançon Cedex, France
| | - C Billet
- FEMTO-ST institute, Univ. Bourgogne Franche-Comté, CNRS, 15B avenue des Montboucons, 25030, Besançon Cedex, France
| | - F Courvoisier
- FEMTO-ST institute, Univ. Bourgogne Franche-Comté, CNRS, 15B avenue des Montboucons, 25030, Besançon Cedex, France.
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9
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Jung M, Fan Z, Shvets G. Midinfrared Plasmonic Valleytronics in Metagate-Tuned Graphene. PHYSICAL REVIEW LETTERS 2018; 121:086807. [PMID: 30192584 DOI: 10.1103/physrevlett.121.086807] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Indexed: 06/08/2023]
Abstract
A valley plasmonic crystal for graphene surface plasmons is proposed. We demonstrate that a designer metagate, placed within a few nanometers of graphene, can be used to impose a periodic Fermi energy landscape on graphene. For specific metagate geometries and bias voltages, the combined metagate-graphene structure is shown to produce complete propagation band gaps for the plasmons, and to impart them with nontrivial valley-linked topological properties. Sharply curved domain walls between differently patterned metagates are shown to guide highly localized plasmons without any reflections owing to suppressed intervalley scattering. Our approach paves the way for nonmagnetic and dynamically reconfigurable topological nanophotonic devices.
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Affiliation(s)
- Minwoo Jung
- Department of Physics, Cornell University, Ithaca, New York 14853, USA
| | - Zhiyuan Fan
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
| | - Gennady Shvets
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
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10
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Abstract
Plasmon hybridization, the electromagnetic analog of molecular orbital theory, provides a simple and intuitive method to describe the plasmonic response of complex nanostructures from the combination of the responses of their individual constituents. Here, we follow this approach to investigate the optical properties of periodic arrays of plasmonic nanoparticles with multiparticle unit cells. These systems support strong collective lattice resonances, arising from the coherent multiple scattering enabled by the lattice periodicity. Due to the extended nature of these modes, the interaction between them is very different from that among localized surface plasmons supported by individual nanoparticles. This leads to a much richer hybridization scenario, which we exploit here to design periodic arrays with engineered properties. These include arrays with two-particle unit cells, in which the interaction between the individual lattice resonances can be canceled or maximized by controlling the relative position of the particles within the unit cell, as well as arrays whose response can be made either invariant to the polarization of the incident light or strongly dependent on it. Moreover, we explore systems with three- and four-particle unit cells and show that they can be designed to support lattice resonances with complex hybridization patterns in which different groups of particles in the unit cell can be selectively excited. The results of this work serve to advance our understanding of periodic arrays of nanostructures and provide a methodology to design periodic structures with engineered properties for applications in nanophotonics.
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Affiliation(s)
- Sebastian Baur
- Department of Physics and Astronomy, University of New Mexico , Albuquerque, New Mexico 87131, United States
| | - Stephen Sanders
- Department of Physics and Astronomy, University of New Mexico , Albuquerque, New Mexico 87131, United States
| | - Alejandro Manjavacas
- Department of Physics and Astronomy, University of New Mexico , Albuquerque, New Mexico 87131, United States
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11
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Miao X, Guo K, Qian C, Wang J, Zhao D, Fung KH. Electron-beam excited photon emission from monopole modes of a plasmonic nano-disc. OPTICS LETTERS 2017; 42:3387-3390. [PMID: 28957111 DOI: 10.1364/ol.42.003387] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 08/03/2017] [Indexed: 05/22/2023]
Abstract
Plasmonic dark modes are not easy to be observed in the far field due to their weak photon emission. By contrast, it has been shown that a dark mode can be excited effectively by a near-field source such as an electron beam. In this Letter, we show theoretically that the photon emission from the monopole-like dark mode supported on a plasmonic nano-disc could be unexpectedly strong when excited by an electron beam through its hole. Even though this monopole mode is considered to be dark, it is found that the emission can be even "brighter" than the dipolar bright modes when the electron speed is higher than 0.6c. Due to the high conversion efficiency from electron energy loss to photon energy, the results could also suggest an optical method for the detection of high-energy electrons passing through the hole with negligible changes in electron speed.
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12
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Jin D, Christensen T, Soljačić M, Fang NX, Lu L, Zhang X. Infrared Topological Plasmons in Graphene. PHYSICAL REVIEW LETTERS 2017; 118:245301. [PMID: 28665651 DOI: 10.1103/physrevlett.118.245301] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Indexed: 06/07/2023]
Abstract
We propose a two-dimensional plasmonic platform-periodically patterned monolayer graphene-which hosts topological one-way edge states operable up to infrared frequencies. We classify the band topology of this plasmonic system under time-reversal-symmetry breaking induced by a static magnetic field. At finite doping, the system supports topologically nontrivial band gaps with mid-gap frequencies up to tens of terahertz. By the bulk-edge correspondence, these band gaps host topologically protected one-way edge plasmons, which are immune to backscattering from structural defects and subject only to intrinsic material and radiation loss. Our findings reveal a promising approach to engineer topologically robust chiral plasmonic devices and demonstrate a realistic example of high-frequency topological edge states.
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Affiliation(s)
- Dafei Jin
- Department of Mechanical Engineering, University of California, Berkeley, California 94720, USA
| | - Thomas Christensen
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Marin Soljačić
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Nicholas X Fang
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Ling Lu
- Institute of Physics, Chinese Academy of Sciences/Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
| | - Xiang Zhang
- Department of Mechanical Engineering, University of California, Berkeley, California 94720, USA
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13
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Cox JD, Silveiro I, García de Abajo FJ. Quantum Effects in the Nonlinear Response of Graphene Plasmons. ACS NANO 2016; 10:1995-2003. [PMID: 26718484 DOI: 10.1021/acsnano.5b06110] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The ability of graphene to support long-lived, electrically tunable plasmons that interact strongly with light, combined with its highly nonlinear optical response, has generated great expectations for application of the atomically thin material to nanophotonic devices. These expectations are mainly reinforced by classical analyses performed using the response derived from extended graphene, neglecting finite-size and nonlocal effects that become important when the carbon layer is structured on the nanometer scale in actual device designs. Here we show that finite-size effects produce large contributions that increase the nonlinear response of nanostructured graphene to significantly higher levels than those predicted by classical theories. We base our analysis on a quantum-mechanical description of graphene using tight-binding electronic states combined with the random-phase approximation. While classical and quantum descriptions agree well for the linear response when either the plasmon energy is below the Fermi energy or the size of the structure exceeds a few tens of nanometers, this is not always the case for the nonlinear response, and in particular, third-order Kerr-type nonlinearities are generally underestimated by the classical theory. Our results reveal the complex quantum nature of the optical response in nanostructured graphene, while further supporting the exceptional potential of this material for nonlinear nanophotonic devices.
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Affiliation(s)
- Joel D Cox
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , Castelldefels, 08860 Barcelona, Spain
| | - Iván Silveiro
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , Castelldefels, 08860 Barcelona, Spain
| | - F Javier García de Abajo
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , Castelldefels, 08860 Barcelona, Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats , Passeig Lluís Companys 23, 08010 Barcelona, Spain
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14
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Wang W, Li BH, Stassen E, Mortensen NA, Christensen J. Localized surface plasmons in vibrating graphene nanodisks. NANOSCALE 2016; 8:3809-3815. [PMID: 26815600 DOI: 10.1039/c5nr08812g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Localized surface plasmons are confined collective oscillations of electrons in metallic nanoparticles. When driven by light, the optical response is dictated by geometrical parameters and the dielectric environment and plasmons are therefore extremely important for sensing applications. Plasmons in graphene disks have the additional benefit of being highly tunable via electrical stimulation. Mechanical vibrations create structural deformations in ways where the excitation of localized surface plasmons can be strongly modulated. We show that the spectral shift in such a scenario is determined by a complex interplay between the symmetry and shape of the modal vibrations and the plasmonic mode pattern. Tuning confined modes of light in graphene via acoustic excitations, paves new avenues in shaping the sensitivity of plasmonic detectors, and in the enhancement of the interaction with optical emitters, such as molecules, for future nanophotonic devices.
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Affiliation(s)
- Weihua Wang
- Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
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