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Conference on Lasers and Electro-Optics Europe (CLEO EUROPE)

作者： Hira Asif Ramazan Sahin Department of Physics Faculty of Science Akdeniz University Antalya Turkey

ISBN: (纸本)9798350345995

Nonlinear plasmon modes (NLPs) supported by metallic nanoparticles play a vital role in enhanced nonlinear optics, high-resolution optical imaging and advanced spectroscopy applications [1]. However, the ultrashort lifetime of these intense nonlinear fields inhibits their effective use in the vast applications of quantum plasmonics. These NLPs formulate through the spatial convolution of fundamental plasmon modes (FM) and decay shortly within 10 fs [2]. FM, being a constituent part, contributes to the intensity and spatiotemporal dynamics of nonlinear plasmonic signal. To acquire pure nonlinear effects, its spectral and temporal independence from the FM is of significant importance. In this paper, we demonstrate the lifetime enhancement of second harmonic (SH) plasmon mode, supported by Au nanoparticle (AuNP), through the resonant coupling with long-lived quantum emitter (QE) (Fig. 1(a) inset) [3]. We utilize coupled harmonic oscillator model and the total Hamiltonian of the system given in Eq.1 consists of eigen energies of plasmon modes ( $\alpha_{j}$ ) and QE, interaction term with coupling strength ( $\kappa$ ), interaction of incident light ( $\omega$ ) and the convolution of FM along with nonlinear susceptibilty $\chi^{(2)}$ .

关键词： finite-difference time-domain method Frequency modulation Modes Nonlinear effects Nonlinear optical devices Optical imaging

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Minimizing the Focal Shift Effect on 2D Metalenses

Minimizing the Focal Shift Effect on 2D Metalenses

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Conference on Lasers and Electro-Optics Europe (CLEO EUROPE)

作者： Serap Aksu Department of Physics Koç University Istanbul Turkey

ISBN: (纸本)9798350345995

For a metalens, which obeys the fundamental laws governed by diffraction, improving the image quality and resolution at the focal region has been the most valuable and desirable feature [1]–[3]. Early classical investigations claim that the principal maximum intensity of the diffracted wave is located at the geometric focus, and the field exhibits definite symmetry about the geometrical focal plane. However, with the extended use of lasers it is shown that during the experiments the principal maximum intensity of the incident wave may not occur at the preset geometrical focus butt may be located closer to the lens. This phenomenon is referred as the ‘focal shift’. One important detrimental result of the focal shift phenomenon is the asymmetric intensity distribution in the focal region [4]–[6]. Thus, reducing the focal shift for a better performing metalens is critical as it leads to a symmetric airy disc like field distribution on focal spot.

关键词： Diffraction optics finite-difference time-domain method High contrast gratings Image quality Image resolution Lenses

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Temporal interfaces by instantaneously varying boundary conditions

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Physical Review B 2022年第9期106卷 094312-094312页

作者： Luca Stefanini Shixiong Yin Davide Ramaccia Andrea Alù Alessandro Toscano Filiberto Bilotti “Roma Tre” University Via Vito Volterra 62 00146 Rome Italy Photonics Initiative Advanced Science Research Center New York New York 10031 USA City College City University of New York New York New York 10031 USA Physics Program Graduate Center City University of New York New York New York 10016 USA

Temporal metamaterials have been recently exploited as a novel platform for conceiving several electromagnetic and optical devices based on the anomalous scattering response arising at a single change or multiple sudden changes in the material properties. However, they are difficult to implement in realistic scenarios by switching the permittivity of a material in time, and new strategies to achieve time interfaces in a feasible manner must be identified. In this paper, we investigate the possibility to realize a temporal metamaterial without acting on the material properties, but rather on the effective refractive index and wave impedance perceived by the wave during the propagation in an empty guiding structure by varying the boundaries in time. We demonstrate analytically and through numerical experiments that suddenly changing the structural dispersion of a parallel-plate waveguide by varying boundary conditions will induce an effective temporal interface. The proposed concept can be extended to temporally controlled metasurfaces, opening an easier path to the design and realization of novel devices based on time-varying metamaterials at microwave and optical frequencies.

关键词： Metamaterials time crystals Waveguides finite-difference time-domain method

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Copper plasmonics with excitons

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Physical Review B 2022年第20期106卷 205404-205404页

作者： David Ziemkiewicz Sylwia Zielińska-Raczyńska Institute of Mathematics and Physics Technical University of Bydgoszcz Al. Prof. S. Kaliskiego 7 85-789 Bydgoszcz Poland

We investigate the propagation of surface plasmons in a thin layer of copper surrounded by copper oxide Cu2O. It is shown that particularly strong excitons in Cu2O can have a considerable impact on plasmon propagation, providing many opportunities for plasmon-exciton and plasmon-plasmon interactions. It is demonstrated that by the use of a sufficiently thin metal layer, one can excite the so-called long range plasmons, which can overcome the inherently high ohmic losses of Cu as compared to the usual plasmonic metals such as silver. Analytical results are confirmed by numerical calculations.

关键词： Excitons Plasmonics Plasmons finite-difference time-domain method

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Ultra-fast tunable optoelectronic full-adder based on photonic crystal ring resonators covered by graphene nanoshells

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PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 2022年第0期142卷

作者： Naghizade, Saleh Saghaei, Hamed Islamic Azad Univ Tabriz Branch Young Researchers & Elite Club Tabriz Iran Islamic Azad Univ Dept Elect Engn Shahrekord Branch Shahrekord Iran Islamic Azad Univ Energy Res Ctr Shahrekord Branch Shahrekord Iran

This paper reports a novel design of a tunable optoelectronic full-adder using two photonic crystal ring resonators (PCRRs). Every PCRR consists of a matrix of silicon rods surrounded by silica rods coated with graphene nanoshells (GNSs). The proposed full-adder is formed by three input ports, two PCRRs, and two output ports for 'SUM' and 'CARRY'. The plane wave expansion technique is used to study the photonic band structure of the fundamental photonic crystal (PhC) microstructure, and the finite-difference time-domain method is also employed in the final design for solving Maxwell's equations to analyze the light propagation inside the structure. We can tune the PhC resonant mode for our desired application by setting the chemical potential of GNSs with an appropriate gate voltage. The numerical results reveal that when the chemical potential of GNSs changes, the switching mechanism occurs and manages the coupling and propagation direction of the input beam inside the structure. We systematically study the effects of physical parameters on the transmission, reflection, and absorption spectra. Our numerical results also demonstrate that the maximum delay is about 0.8 ps. The 663 mu m(2) area of the proposed full-adder based on two-dimensional materials makes it a building block of every photonic integrated circuit used for data processing systems.

关键词： Full-adder Graphene nanoshell Photonic crystal Chemical potential Gate voltage Plane wave expansion method finite-difference time-domain method

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Active control of thermal emission by graphene-nanowire coupled plasmonic metasurfaces

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Physical Review B 2022年第11期106卷 115416-115416页

作者： Jiayu Li Zhuo Li Xiu Liu Stanislav Maslovski Sheng Shen Department of Mechanical Engineering Carnegie Mellon University Pittsburgh Pennsylvania 15213 USA Instituto de Telecomunicações and Department of Electronics Telecommunications and Informatics University of Aveiro Campus Universitário de Santiago 3810-193 Aveiro Portugal

Metasurfaces, together with graphene plasmonics, have become prominent for the emissivity control in thermal engineering, both passively, through changing the geometric parameters and packing density of the metasurfaces, and actively, through graphene gating or doping. We demonstrate a graphene-nanowire coupled plasmonic metasurface utilizing the hybrid localized surface plasmon modes of the nanowire array and graphene. The nanowire array makes the hybrid surface plasmon mode localized, allowing a free-space excitation. The single-layer graphene, via the gating between the underneath mirror and a top electrode, can actively tune the spectral emissivity by almost 90%. In addition, the graphene surface plasmon modes remove the strict polarization dependence of nanowire array emission, resulting in a fivefold enhancement of the P-polarized emissivity, especially for large emission angles.

关键词： Metasurfaces Plasmonics Graphene finite-difference time-domain method

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Reciprocity condition in synchronously time-periodic bianisotropic materials

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Physical Review B 2022年第21期106卷 214301-214301页

作者： Somayeh Boshgazi Mohammad Memarian Khashayar Mehrany Behzad Rejaei Department of Electrical Engineering Sharif University of Technology Tehran Iran

In this paper, a sufficient reciprocity condition for general time-periodic modulated bianisotropic media is extracted from first principles. Reciprocity of various cases of significant importance, including stationary bianisotropic media, time-varying (TV) isotropic media, TV anisotropic media, and TV bianisotropic media, are investigated using this condition. We prove that synchronous time modulation of stationary bianisotropic yet reciprocal media (chiral, pseudochiral, and achiral) does not lead to nonreciprocity, unless the modulation function breaks time reversal symmetry. This is in contrast to recently published research. The theoretical results are validated using in-house finite difference time domain simulations.

关键词： Magnetoelectric effect Non-reciprocal transmission Metamaterials Bloch wave theory Bloch-Floquet theorem Electromagnetic wave theory finite-difference time-domain method Materials modeling T-symmetry

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Transport through Amorphous Photonic Materials with Localization and Bandgap Regimes

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Physical Review Letters 2022年第15期129卷 157402-157402页

作者： Frank Scheffold Jakub Haberko Sofia Magkiriadou Luis S. Froufe-Pérez Department of Physics University of Fribourg CH-1700 Fribourg Switzerland Faculty of Physics and Applied Computer Science AGH University of Science and Technology Aleja Mickiewicza 30 Krakow 30-059 Poland

We propose a framework that unifies the description of light transmission through three-dimensional amorphous dielectric materials that exhibit both localization and a photonic bandgap. We argue that direct, coherent reflection near and in the bandgap attenuates the generation of diffuse or localized photons. Using the self-consistent theory of localization and considering the density of states of photons, we can quantitatively describe the total transmission of light for all transport regimes: transparency, light diffusion, localization, and bandgap. Comparison with numerical simulations of light transport through hyperuniform networks supports our theoretical approach.

关键词： Anderson localization Photonic crystals Photonics Scattering theory Disordered systems Diffusion & random walks finite-difference time-domain method Light scattering

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Optical sensing in single-mode filters base on surface plasmon H-shaped cavities

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OPTICS COMMUNICATIONS 2022年 505卷 127534-127534页

作者： Khani, Shiva Hayati, Mohsen Razi Univ Fac Engn Elect Engn Dept Kermanshah *** Iran

Three novel refractive index (RI) sensors based on one, two, and three H-shaped cavities (HCs) and metal- insulator-metal (MIM) waveguides are proposed in this paper. By coupling more than one HC (two and three), the Q-factor and then the FOM value of the designed RI sensors increase. A well-known method for increasing the sharpness transition between the passband and stopband of a spectrum is coupling cavities together. Fortunately, the proposed HC has such a property that increases the FOM value. The maximum obtained FOM of the proposed sensors using one, two, and three HCs reached 69.5, 100.19, and 108.36 RIU-1, respectively. Three proposed plasmonic structures which are used to design RI sensors have single-mode spectra in a wide wavelength range of 500 to 2000 nm. A single-mode spectrum is easier to cope with in circuits with higher complexity such as RI sensors. The metal and insulator materials that are used in the designed structures are silver and air, respectively. The finite-difference time-domain (FDTD) method is used for the numerical investigation of the proposed RI sensors. To verify FDTD simulations, the basic rectangular cavity which is used to design HC is analyzed using an analytical method. In summary, the benefits of the proposed RI sensors are having single-mode spectra in a wide wavelength range and also their simple structures. The proposed topology easily be redesigned and adapted with different numbers of HCs without disturbing its single-mode spectrum to achieve various FOM values. Furthermore, considering the fact that the proposed cavity is based on rectangular shapes, it has a simple fabrication process. Taking into account the mentioned advantages of the proposed structures, they can be used in integrated optical circuits for optical communication purposes.

关键词： Surface plasmon polaritons Refractive index sensor H-shaped cavity Metal-insulator-metal waveguide finite-difference time-domain method

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Quantum-Coherent Light-Electron Interaction in a Scanning Electron Microscope

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Physical Review Letters 2022年第23期128卷 235301-235301页

作者： R. Shiloh T. Chlouba P. Hommelhoff Physics Department Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) Staudtstraße 1 91058 Erlangen Germany.

The last two decades experimentally affirmed the quantum nature of free electron wave packets by the rapid development of transmission electron microscopes into ultrafast, quantum-coherent systems. So far, all experiments were restricted to the bounds of transmission electron microscopes enabling one or two photon-electron interaction sites. We show the quantum coherent coupling between electrons and light in a scanning electron microscope, at unprecedentedly low, subrelativistic energies down to 10.4 keV. These microscopes not only afford the yet-unexplored energies from ∼0.5 to 30 keV providing the optimum electron-light coupling efficiency, but also offer spacious and easily configurable experimental chambers for extended, cascaded optical set ups, potentially boasting thousands of photon-electron interaction sites. Our results make possible experiments in electron wave packet shaping, quantum computing, and spectral imaging with low-energy electrons.

关键词： Electron beams & optics Near-field optics Quantum computation Quantum measurements Semiclassical physics Ultrafast optics Electron techniques finite-difference time-domain method Scanning electron microscopy

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