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Scaling Relations of Plasmon Resonance Peak in Au@Fe3O4 Core-Shell Nanohybrids Structure
摘要： In this paper, we study the absorption efficiency spectra of Au nanoparticles enveloped with Fe3O4 nanoshell by applying the discrete dipole approximation method. Three kinds of Au@Fe3O4 core-shell nanohybrids (NHs) structure, including the same core with different shell thickness, the same outer shell with different core radius, and the same size of total radius, have been discussed in detail. The simulation results show that the square of localized surface plasmon resonance (LSPR) peak wavelength of NHs is linearly proportional with the volume fraction of the shell, regardless of the outer shell material properties. Compared to the plasmon resonance peak of the Au nanoparticles, the LSPR shift of the NHs is dependent on both the total particles size and the outer Fe3O4 shell thickness. Our calculation results would provide some key guidances to design the structure variables of NHs for a broad range of plasmon applications.
关键词： Nanohybrids,Discrete dipole approximation,Absorption efficiency
更新于2025-09-23 15:23:52
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Scattering of an Airy light-sheet by a non-spherical particle using discrete dipole approximation
摘要： The scattering of an Airy light-sheet by a non-spherical particle is investigated using the discrete dipole approximation (DDA). The internal and near-surface fields of the cube placed in an Airy light-sheet are calculated, and the effects of the transverse dimension factor w0, the attenuation factor a, and beam center z0 are mainly discussed. w0 can increase the number of side lobes incident on the target, thereby increase the wave jet energy. Increasing the attenuation coefficient a leads to less wave jet energy. By moving the light-sheet, the side lobe of the incident light-sheet increases, and the wave jet energy increases. Potential applications include optical manipulation of particles, particle sizing, optical imaging, etc.
关键词： Scattering,Airy light-sheet,Angular spectrum decomposition method,Discrete dipole approximation (DDA)
更新于2025-09-23 15:23:52
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Nonreciprocal optical links based on time-modulated nanoantenna arrays: Full-duplex communication
摘要： Interference of transmitted and received signals hinders the simultaneous functionality of a conventional optical antenna as a transmitter and receiver which is required for full-duplex communication. The full-duplex communication schemes enabled by dense wavelength division multiplexed optical networks require distinct transmitter/receiver components operating at different wavelengths which increase the cost, complexity, and footprint of the physical layer. In this work, we demonstrate that an array of nanoantennas with leaky-wave architecture based on spatiotemporal modulation establishes nonreciprocal optical links which can reject the interference of transmitted and received signals by isolating the frequency of transmission and reception modes. For this purpose, we integrate indium-tin oxide into plasmonic nanodipoles which allows for realization of time-modulated nanoantennas in near-infrared frequency regime through electrical modulation of charge carrier density with radio-frequency signals. The radiation characteristics of individual nanoantennas and modal properties of nanoantenna arrays are rigorously studied through linking of charge transport and electromagnetic models. To this end, we extend the formulation of discrete dipole approximation as the standard modeling tool for electromagnetic scattering from nanoantenna arrays to treat realistic time-modulated structures with drastically different timescales between optical and modulation frequencies. The operation of spatiotemporally modulated array antennas in transmission and reception modes is investigated. Moreover, electrical beam-scanning functionality and dependence of antenna characteristics to modulation parameters and wavelength are demonstrated. It is rigorously established that such array antennas can operate as full transceivers by separating the transmitted and received signals propagating along the same direction through down conversion and up conversion of the frequency. Our results provide a route toward realization of optical antenna systems capable of full-duplex communication and real-time beam scanning which can increase the capacity and decrease the complexity of optical networks.
关键词： nonreciprocal optical links,indium-tin oxide,leaky-wave antenna,discrete dipole approximation,full-duplex communication,time-modulated nanoantenna arrays,spatiotemporal modulation
更新于2025-09-23 15:23:52
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Quality factor assessment of finite-size all-dielectric metasurfaces at the magnetic dipole resonance
摘要： Recently there has been a large interest in achieving metasurface resonances with large quality factors. In this article, we examine metasurfaces that comprised a finite number of magnetic dipoles oriented parallel or orthogonal to the plane of the metasurface and determine analytic formulas for their resonances’ quality factors. These conditions are experimentally achievable in finite-size metasurfaces made of dielectric cubic resonators at the magnetic dipole resonance. Our results show that finite metasurfaces made of parallel (to the plane) magnetic dipoles exhibit low quality factor resonances with a quality factor that is independent of the number of resonators. More importantly, finite metasurfaces made of orthogonal (to the plane) magnetic dipoles lead to resonances with large quality factors, which ultimately depend on the number of resonators comprising the metasurface. In particular, by properly modulating the array of dipole moments by having a distribution of resonator polarizabilities, one can potentially increase the quality factor of metasurface resonances even further. These results provide design guidelines to achieve a sought quality factor applicable to any resonator geometry for the development of new devices such as photodetectors, modulators, and sensors.
关键词： dipole approximation,Mie resonances,magnetic dipole resonance,finite-size metasurfaces,High quality factor
更新于2025-09-23 15:22:29
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[IEEE 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Odessa, Ukraine (2018.9.4-2018.9.7)] 2018 9th International Conference on Ultrawideband and Ultrashort Impulse Signals (UWBUSIS) - Time Domain Modelling of Pulse Wave Scattering on Small Metal Spheres
摘要： We consider a short pulse plane wave incident on a small metal sphere. The scattered field from the sphere can be presented as a multipole expansion over spherical harmonics. For small spheres (compared to the signal duration) the scattered field will be mainly presented by the dipole component. So we find in a closed form and analyze the convolution operator that relates the induced dipole moment (both electric and magnetic dipoles are considered) to the incident electric field waveform. The numerical approach to calculate scattering from several such spheres is described.
关键词： transient electric dipole,discrete dipole approximation,induced dipole moment,closed-form solution,transient diffraction
更新于2025-09-23 15:21:21
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Up-Conversion Luminescence Properties of Lanthanide-Gold Hybrid Nanoparticles as Analyzed with Discrete Dipole Approximation
摘要： Up-conversion nanoparticles (UCNP) under near-infrared (NIR) light irradiation have been well investigated in the field of bio-imaging. However, the low up-conversion luminescence (UCL) intensity limits applications. Plasmonic modulation has been proposed as an effective tool to adjust the luminescence intensity and lifetime. In this study discrete dipole approximation (DDA) was explored concerning guiding the design of UCNP@mSiO2-Au structures with enhanced UCL intensity. The extinction effects of gold shells could be changed by adjusting the distance between the UCNPs and the Au NPs by synthesized tunable mesoporous silica (mSiO2) spacers. Enhanced UCL was obtained under 808 nm irradiation. The original theoretical predictions could not be demonstrated to full extend by experimental data, indicating that better models for simulation need to take into account in homogeneities in particle morphologies. Yet, one very certain conclusion resulting from the DDA calculations and experiments is that the absorbance can blue-shift with more Au NPs added and the absorbance can-red shift for samples with enhanced silica sizes in the UCNP@mSiO2-Au structures. Furthermore, when the DDA model is more consistent with the practical structure (dispersed Au NPs instead of Au shell), the theoretical absorbance occurs almost the same as the practical absorbance. All in all, the DDA could fit the extinction effect of Au perfectly and be suitable for guiding how to design the UCNP and Au.
关键词： lanthanide-based composites,surface plasmon resonance,up conversion nanoparticles,discrete dipole approximation
更新于2025-09-23 15:21:01
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Correlation between Near-Field Enhancement and Dephasing Time in Plasmonic Dimers
摘要： Near-field enhancement and dephasing time play critical roles in several applications of localized surface plasmon resonance. Here, using an example gold dimer system, we reveal the correlation between the near-field enhancement and dephasing time via time-resolved photoemission electron microscopy. Compared with isolated particles, dimers with small gap sizes show stronger near-field enhancement and shorter dephasing times. These results are well reproduced by numerical simulations and further explained by a coupled dipole approximation model. The roles of near- and far-field coupling and plasmon localization in balancing near-field enhancement and dephasing time are also unveiled.
关键词： dephasing time,time-resolved photoemission electron microscopy,near-field enhancement,plasmonic dimers,coupled dipole approximation model
更新于2025-09-23 15:19:57
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Direct prediction of bidirectional reflectance by dense particulate deposits
摘要： To observe and study the effects of the volume packing density on polarimetric scattering by deposited particulate materials, a comparison is made between the vector radiative transport equation (VRTE) and the plane wave plane parallel (PWPP) models for the polarized bidirectional reflectance and transmittance from plane parallel layers of randomly distributed, wavelength–sized particles. Calculations have been performed on ice and mineral materials with refractive indices of m = 1.31 and m = 1.5 + 0.01i respectively. In these simulations, particle volume fraction ranges from around 0.05–0.3 for deposits consisting of spherical particles with size parameters of one and two. It is found that the PWPP model results converge to those predicted by the VRTE at small (～5% or less) particle volume fractions. At higher volume fractions, the difference between the PWPP and VRTE results depends strongly on the particle size and refractive index, yet not so much on the optical thickness (equivalently, volume of particles per unit area of layer). PWPP simulation results of coherent backscattering effects – brightness opposition and polarization opposition effects – for ice and mineral particles are also represented. Their dependency on the particle volume fraction and particle size has been discussed.
关键词： Radiative transfer theory,Densely packed media,Coherent backscattering and polarization opposition effects,Plane parallel media,Adding and doubling,Periodic discrete dipole approximation,Multiple scattering
更新于2025-09-19 17:15:36
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Plasmonic coupling in closed-packed ordered gallium nanoparticles
摘要： plasmonic gallium (Ga) nanoparticles (nps) are well known to exhibit good performance in numerous applications such as surface enhanced fluorescence and Raman spectroscopy or biosensing. However, to reach the optimal optical performance, the strength of the localized surface plasmon resonances (LSPRs) must be enhanced particularly by suitable narrowing the NP size distribution among other factors. With this purpose, our last work demonstrated the production of hexagonal ordered arrays of Ga NPs by using templates of aluminium (Al) shallow pit arrays, whose LSPRs were observed in the VIS region. The quantitative analysis of the optical properties by spectroscopic ellipsometry confirmed an outstanding improvement of the LSPR intensity and full width at half maximum (FWHM) due to the imposed ordering. Here, by engineering the template dimensions, and therefore by tuning Ga NPs size, we expand the LSPRs of the Ga NPs to cover a wider range of the electromagnetic spectrum from the UV to the IR regions. More interestingly, the factors that cause this optical performance improvement are studied with the universal plasmon ruler equation, supported with discrete dipole approximation simulations. the results allow us to conclude that the plasmonic coupling between nps originated in the ordered systems is the main cause for the optimized optical response.
关键词： plasmonic coupling,gallium nanoparticles,spectroscopic ellipsometry,discrete dipole approximation,localized surface plasmon resonances
更新于2025-09-19 17:13:59
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Wulff-Based Approach to Modeling the Plasmonic Response of Single Crystal, Twinned, and Core–Shell Nanoparticles
摘要： The growing interest in plasmonic nanoparticles and their increasingly diverse applications is fuelled by the ability to tune properties via shape control, promoting intense experimental and theoretical research. Such shapes are dominated by geometries that can be described by the kinetic Wulff construction such as octahedra, thin triangular platelets, bipyramids, and decahedra, to name a few. Shape is critical in dictating the optical properties of these nanoparticles, in particular their localized surface plasmon resonance behavior, which can be modeled numerically. One challenge of the various available computational techniques is the representation of the nanoparticle shape. Specifically, in the discrete dipole approximation, a particle is represented by discretizing space via an array of uniformly distributed points-dipoles; this can be difficult to construct for complex shapes including those with multiple crystallographic facets, twins, and core?shell particles. Here, we describe a standalone user-friendly graphical user interface (GUI) that uses both kinetic and thermodynamic Wulff constructions to generate a dipole array for complex shapes, as well as the necessary input files for DDSCAT-based numerical approaches. Examples of the use of this GUI are described through three case studies spanning different shapes, compositions, and shell thicknesses. Key advances offered by this approach, in addition to simplicity, are the ability to create crystallographically correct structures and the addition of a conformal shell on complex shapes.
关键词： localized surface plasmon resonance,Wulff construction,plasmonic nanoparticles,shape control,graphical user interface,DDSCAT,discrete dipole approximation
更新于2025-09-16 10:30:52