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Electrically tunable graphene‐metal metasurfaces with controllable optical properties have attracted interest for straightforward manipulation of free space light. Their resonance tuning range depends on graphene's electrical transport characteristics, which are affected by its quality, operating conditions, and the device design. An important example of the latter is the direct contact of metallic antennas with the graphene layer that limits the extent to which a bias voltage can tune the metasurface's permittivity. In this work, this issue is resolved in a straightforward and fabrication‐efficient way for graphene‐metal hybrid metasurfaces with multiple plasmonic resonances. It is demonstrated that the incorporation of a 10 nm Al2O3 barrier layer enhances the tuning range of mid‐infrared resonances compared to metasurfaces without barrier layer, i.e., from 300 to 700 nm for a 7.3 µm resonance and from 110 to 140 nm for a 4.7 µm resonance. The improved tunability of the metal/dielectric/graphene metasurface can be attributed to the reduced electrical coupling between metal and graphene, as confirmed by an equivalent circuit model. These results bring closer the use of active metasurfaces based on two‐dimensional materials under ambient conditions, with possible applications as optical filters, modulators, and information processing devices that require dynamic control of light. [ABSTRACT FROM AUTHOR]

An effective performance enhancement model for the thin film solar cell conjointly based on extraordinary transmission and nanoantenna is proposed and investigated. The absorber layer of the extraordinary transmission based solar cell contains a metallic thin film with periodic holes. Maximum extraordinary transmission is accomplished as the metallic film has the same refractive index on both sides. Increased light transmission causes the absorber layer to absorb more light, which increases short circuit current density and subsequently the efficiency of the thin film solar cell. The presented analysis demonstrates that adding a square nano patch on the top surface of the absorber layer can further boost the extraordinary transmission. The extraordinary transmission is increased because of the formation of cavity nanoantenna. Cavity nanoantenna increases the coupling of light into the hole due to the excitation of surface plasmons polaritons. The proposed design of solar cell exhibits around 98% absorption and the short circuit current density is increased by a factor of 3.23. The study has been carried out using finite difference time domain (FDTD) method.

An efficient structure of thin film solar cell (TFSC) is designed and investigated using a plasmonic nanoantenna for improving the performance of the solar cell. The proposed design is formed as a shape of "Swastika," an ancient geometrical figure, designed by bending the conventional dipole antenna up to optimal lengths. The designed antenna is positioned on the top of the absorber layer which is made up with amorphous silicon and is topped with an anti-reflection layer of Indium Tin Oxide. Due to Swastika shape, the structure equally responds to the different polarized waves and becomes polarization-insensitive and thus can significantly enhance the performance of the thin-film solar cells. The new design confines the electric field in a larger area. This confinement is due to the presence of additional feed gaps produced by bending the conventional dipole antenna, increasing the absorption. The simulation results show that the design provides an absorption enhancement of 99.2% in the absorber layer. [ABSTRACT FROM AUTHOR]

The results of a theoretical study of the behavior of a system of nanophotonic devices, consisting of receiving and transmitting plasmonic metal antennas, are presented. Based on the finite element method, the main parameters of antennas located in the TSV channel and receiving a signal in the terahertz frequency range are calculated. The limiting range of signal transmission and the coefficient of its amplification are determined. Conclusions are drawn on the suitability of the presented configuration as a system for wireless data transmission and reception in three-dimensional integrated circuits. [ABSTRACT FROM AUTHOR]

Electrons injected into one-dimensional (1D) metals are efficiently converted into infrared plasmons because the unique property of the Luttinger liquid, a strongly correlated electronic matter in one-dimensional (1D) metals, prohibits excitations of other quasiparticles. Using the Luttinger liquid behavior, the electrically driven 1D metals can be used as a feed for optical nanoantennas. Nanoantennas can couple the 1D Luttinger liquid plasmons in the feed to the radiating photons in free space. In this work, we suggest design principles for the 1D metallic Luttinger liquid feed and the nanoantennas to obtain high injection and radiation efficiencies, respectively. We expect that our work can promote experimental efforts to realize electrically driven Luttinger liquid-fed nanoantennas and efficient infrared light sources. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Two plasmonic nanoantenna configurations—nanodisk and nanostrip arrays—in a metal–insulator-metal (MIM) setup were proposed, optimized, and compared by simulating their optical properties in three-dimensional models using COMSOL Multiphysics software. The optical responses, including electric field enhancement, absorption, reflection, and transmission spectra, were systematically investigated. Optimized geometrical parameters led to a significant enhancement of the electric field within the gap layers and almost perfect light absorptance for both structures. The results showed that the enhancement of the electric field depends on the polarization of the incident light. For both polarizations, the periodic circular nanodisk array showed a stronger field enhancement with an electric field enhancement factor of 6.6 × 106 and TE polarization, and a larger absorptance of 98% at its dipole resonance wavelength, indicating the fundamental plasmonic mode. In addition, weaker resonant modes were observed in the absorptance and reflectance spectra of both nanostructures, with the nanostrips exhibiting sharper and stronger higher-order modes, making them suitable for applications requiring precise wavelength selectivity and narrow-band responses. Despite their different geometric shapes, both structures exhibited similar optimized metal film thickness and nanoparticle height, comparable modes in number and position, and identical optimized light incidence angles. Furthermore, increasing the dielectric gap layer thickness and optimizing it to a specific value revealed its ability to measure the refractive index, making it a promising candidate for sensing applications. [ABSTRACT FROM AUTHOR]

Controlling directionality of optical emitters is of utmost importance for their application in communication and biosensing devices. Metallic nanoantennas have been proven to affect both excitation and emission properties of nearby emitters, including the directionality of their emission. In this regard, optical directional nanoantennas based on a Yagi–Uda design have been demonstrated in the visible range. Despite this impressive proof of concept, their overall size (~λ2/4) and considerable number of elements represent obstacles for the exploitation of these antennas in nanophotonic applications and for their incorporation onto photonic chips. In order to address these challenges, we investigate an alternative design. In particular, we numerically study the performance of a recently demonstrated "ultracompact" optical antenna based on two parallel gold nanorods arranged as a side-to-side dimer. Our results confirm that the excitation of the antiphase mode of the antenna by a nanoemitter placed in its near-field can lead to directional emission. Furthermore, in order to verify the feasibility of this design and maximize the functionality, we study the effect on the directionality of several parameters, such as the shape of the nanorods, possible defects in the dimer assembly, and different positions and orientations of the nanoemitter. We conclude that this design is robust to structural variations, making it suitable for experimental upscaling. [ABSTRACT FROM AUTHOR]

Coherent perfect absorption (CPA) describes the absence of all outgoing modes from a lossy resonator, driven by lossless incoming modes. Here, we show that for nanoresonators that also exhibit radiative losses, e.g., plasmonic nanoantennas, a generalized version of CPA (gCPA) can be applied. In gCPA outgoing modes are suppressed only for a subset of (guided plasmonic) modes while other (radiative) modes are treated as additional loss channels - a situation typically referred to as perfect impedance matching. Here we make use of gCPA to show how to achieve perfect impedance matching between a single nanowire plasmonic waveguide and a plasmonic nanoantenna. Antennas with both radiant and subradiant characteristics are considered. We further demonstrate potential applications in background-free sensing.

Thermally induced particle hopping in the nanoscale double-well potential is fundamental in material design and device operation. After the proposal of the basic hopping theory, several experimental studies, including some using the optical trapping method, have validated the theoretical approach over various friction ranges of the surrounding medium. However, only external parameters, such as viscosity, temperature, and pressures, have been varied in practical circumstances, and other tools capable of adjusting the potential profile itself to modulate the hopping rate are needed. By using metallic nanoantenna with various gap sizes and different optical pump power, we engineered a double-well potential landscape and directly observed the hopping of a single nanoparticle with a diameter of 4 nm. The distance between the two potential wells was 0.6–5 nm, and the maximum well depth and maximum height of the central potential barrier were approximately 69 and 4 kBT, respectively. The hopping rate was governed by the Arrhenius law and showed a vertex when the barrier height was approximately 2 kBT, which was in good agreement with the computational expectations.

Concepts adapted from radio frequency devices have brought forth subwavelength scale optical nanoantenna, enabling light localization below the diffraction limit. Beyond enhanced light–matter interactions, plasmonic nanostructures conjugated with active materials offer strong and tunable coupling between localized electric/electrochemical/mechanical phenomena and far-field radiation. During the last two decades, great strides have been made in development of active plasmonic nanoantenna (PNA) systems with unconventional and versatile optical functionalities that can be engineered with remarkable flexibility. In this review, we discuss fundamental characteristics of active PNAs and summarize recent progress in this burgeoning and challenging subfield of nano-optics. We introduce the underlying physical mechanisms underpinning dynamic reconfigurability and outline several promising approaches in realization of active PNAs with novel characteristics. We envision that this review will provide unambiguous insights and guidelines in building high-performance active PNAs for a plethora of emerging applications, including ultrabroadband sensors and detectors, dynamic switches, and large-scale electrophysiological recordings for neuroscience applications.

Optical nanoantennas can efficiently harvest electromagnetic energy from nanoscale space and boost the local radiation to the far field. The dielectric-metal nanogap is a novel design that can help to overcome the core issue of optical loss in all-metal nanostructures while enabling photon density of states larger than that in all-dielectric counterparts. This article reports that a crystalline spherical silicon nanoparticle on metal film (SiNPoM) nanoantenna can largely enhance the spontaneous emission intensity of quantum dots by an area-normalized factor of 69 and the decay rate by 42-fold compared with quantum dots on glass. A high total quantum efficiency of over 80%, including ~20% for far-field radiation and ~60% for surface plasmon polaritons, is obtained in simulation. Thanks to not only the low optical loss in dielectric nanoparticles but also the appropriate gap thickness which weakens the non-radiative decay due to the quenching from metal. Mie resonant modes additionally provide the flexible control of far-field emission patterns. Such a simple optical nanoantenna can be combined with various nanoscale optical emitters and easily extended to form large area metasurfaces functioning as active regions in light-emitting devices in applications such as advanced display, wireless optical communication, and quantum technology.

The phase matching between the propagating fundamental and nonlinearly generated waves plays an important role in the efficiency of the nonlinear frequency conversion in macroscopic crystals. However, in nanoscale samples, such as nanoplasmonic structures, the phase-matching condition is often ignored due to the sub-wavelength nature of the materials. Here, we first show that the phase matching of the lattice plasmon modes at the fundamental and second-harmonic frequencies in a plasmonic nanoantenna array can effectively enhance the surface-enhanced second-harmonic generation. Additionally, a significant enhancement of the second-harmonic generation is demonstrated using stationary band-edge lattice plasmon modes with zero phase.

Optical nanoantenna is a key component in plasmonic circuitry, which can receive or transmit an electromagnetic field in the near field of an object (nanomaterials). It has wide range of applications including surface‐enhanced Raman scattering (SERS), photocatalytic reactions, remote SERS, solar cell, plasmonic nanoscopy, and quantum plasmonics. The main challenges in optical nanoantenna research include both fundamental understanding of the underlying physics and issues related to fabrication of low cost, high throughput nanostructures beyond the diffraction limit. The nanoscale feature size of optical antennas limits our ability to design, manufacture, and characterize their resonant behavior. This review investigates the fabrication methods and SERS applications of optical nanoantenna. [ABSTRACT FROM AUTHOR]

Copyright of SDU Journal of Engineering Sciences & Design / Mühendislik Bilimleri ve Tasarım Dergisi is the property of Journal of Engineering Sciences & Design and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The evolution of nanotechnology has provided a better understanding of light-matter interaction at a subwavelength scale and has led to the development of new devices that can possibly play an important role in future applications. Nanoantennas are an example of such devices, having gained interest in recent years for their application in the field of photovoltaic technology at visible and infrared wavelengths, due to their ability to capture and confine energy of free-propagating waves. This property results from a unique phenomenon called extraordinary optical transmission (EOT) where, due to resonant behavior, light passing through subwavelength apertures in a metal film can be transmitted in greater orders of magnitude than that predicted by classical theories. During this study, 2D and 3D models featuring a metallic nanoantenna array with subwavelength holes coupled to a photovoltaic cell are simulated using a Finite Element Tool. These models present with slight variations between them, such as the position of the nanoantenna within the structure, the holes’ geometry and the type of cell, in order to verify how its optical response is affected. The results demonstrate that the coupling of nanoantennas to solar cells can be advantageous and improve the capture and absorption of radiation. It is concluded that aperture nanoantennas may concentrate radiation, meaning that is possible to tune the electric field peak and adjust absorption on the main layers. This may be important because it might be possible to adjust solar cell performance to the global regions’ solar spectrum by only adjusting the nanoantenna parameters.

The large cross sections and strong confinement provided by the plasmon resonances of metallic nanostructures make these systems an ideal platform to implement nanoantennas. Like their macroscopic counterparts, nanoantennas enhance the coupling between deep subwavelength emitters and free radiation, providing, at the same time, an increased directionality. Here, inspired by the recent works in parity-time symmetric plasmonics, we investigate how the combination of conventional plasmonic nanostructures with active materials, which display optical gain when externally pumped, can serve to enhance the performance of metallic nanoantennas. We find that the presence of gain, in addition to mitigating the losses and therefore increasing the power radiated or absorbed by an emitter, introduces a phase difference between the elements of the nanoantenna that makes the optical response of the system directional, even in the absence of geometrical asymmetry. Exploiting these properties, we analyse how a pair of nanoantennas with balanced gain and loss can enhance the far-field interaction between two dipole emitters. The results of this work provide valuable insight into the optical response of nanoantennas made of active and passive plasmonic nanostructures, with potential applications for the design of optical devices capable of actively controlling light at the nanoscale. [ABSTRACT FROM AUTHOR]

A modification to the conventional anti-reflection coating (ARC) is proposed to improve the performance of the amorphous silicon solar cells. The performance is improved by replacing the conventional anti-reflection coating (ARC) by a modified ARC. The modified ARC has an embedded array of silver Yagi–Uda nanoantenna. Due to the highly directive and broadband characteristics of Yagi–Uda nanoantenna, the modified ARC minimizes the reflection over large range wavelengths and guides the incoming solar radiation towards absorber layer effectively which results in increased absorption and subsequent increase in the short-circuit current density. Solar cell with proposed ARC exhibits 1.66 times improved short-circuit current density and 1.43 times increased conversion efficiency. To the best of our knowledge, this is the first report on a Yagi–Uda nanoantenna incorporated in a solar cell to improve its performance. [ABSTRACT FROM AUTHOR]

Mainly manipulating emitted waves via plasmonic resonance is a fundamental characteristic of optical antennas. Plasmonic nanoantennas are used for terahertz (THz) radiation caused by optical interaction with surface resonance. The designed nanoantenna is such that the plasmonic resonance of the nanoantenna changes by controlling the graphene chemical potential (μ c) from 0 eV to 0.2 eV. Although a dielectric layer separates the trapezoidal graphene sheets, an essential difference in the scattering parameters and the radiation pattern is observed since an external direct current bias changed the graphene surface impedance to about 860 Ω, which is the optimal value for reducing return loss in nano-systems. In other words, the plasmonic resonance frequencies can be tuned by the effect of a localised electrostatic field. Also, the trapezoidal graphene-based plasmonic nanoantenna has a high quality factor (Q-factor) from 2.35 to 5.71. Therefore, dynamic control, enhancing the input impedance and stable efficiency of graphene-based plasmonic nanoantennas, improves performance and matching at THz nano-systems for many applications of optoelectronic devices. • The designed nanoantenna is such that the plasmonic resonance of the nanoantenna changes by controlling the graphene chemical potential (μc) from 0 eV to 0.2 eV. • The effect of a localised electrostatic field can tune the plasmonic resonance frequencies. • Dynamic control, enhancing the input impedance and stable efficiency of graphene-based plasmonic nanoantennas, improves performance and matching at THz nanosystems for many applications of optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this paper, systematic study for asymmetric tapered dipole nanoantenna is implemented using finite element frequency domain (FEFD) solver where harvesting efficiency, field confinement, surface current, and input impedance are calculated at wavelength of 500 nm. The proposed nanoantennas achieve a harvesting efficiency of 61.3% and a field enhancement factor of 37.7 over the conventional dipole nanoantenna. This enhancement is attributed to the irregularity of the surface current distribution on the asymmetric designs. Particle swarm optimization technique is used to find the optimum design geometrical parameters through an external link between the optimization algorithm and the FEFD solver. Moreover, the proposed designs offer a resonance impedance of 500 Ω to match that of fabricated rectifiers. Further study of the structure fabrication tolerance is included which shows the robustness of the proposed nanoantennas. [ABSTRACT FROM AUTHOR]

Plasmonic nanoantennas can significantly enhance the light–matter interactions at the nanoscale, and as a result have been used in a variety of applications such as sensing molecular vibrations in the infrared range. Indium–tin–oxide (ITO) shows metallic behavior in the infrared range, and can be used for alternative plasmonic materials. In this work, we numerically studied the optical properties of hexagonal ITO nanodisk and nanohole arrays in the mid-infrared. Field enhancement up to 10 times is observed in the simulated ITO nanostructures. Furthermore, we demonstrated the sensing of the surface phonon polariton from a 2-nm thick SiO2 layer under the ITO disk arrays. Such periodic arrays can be readily fabricated by colloidal lithography and dry etching techniques; thus, the results shown here can help design efficient ITO nanostructures for plasmonic infrared applications.

Nanoantennas offer the ultimate spatial control over light by concentrating optical energy well below the diffraction limit, whereas their quality factor (Q) is constrained by large radiative and dissipative losses. Dielectric microcavities, on the other hand, are capable of generating a high Q-factor through an extended photon storage time but have a diffraction-limited optical mode volume. Here we bridge the two worlds, by studying an exemplary hybrid system integrating plasmonic gold nanorods acting as nanoantennas with an on-resonance dielectric photonic crystal (PC) slab acting as a low-loss microcavity and, more importantly, by synergistically combining their advantages to produce a much stronger local field enhancement than that of the separate entities. To achieve this synergy between the two polar opposite types of nanophotonic resonant elements, we show that it is crucial to coordinate both the dissipative loss of the nanoantenna and the Q-factor of the low-loss cavity. In comparison to the antenna–cavity coupling approach using a Fabry–Perot resonator, which has proved successful for resonant amplification of the antenna's local field intensity, we theoretically and experimentally show that coupling to a modest-Q PC guided resonance can produce a greater amplification by at least an order of magnitude. The synergistic nanoantenna-microcavity hybrid strategy opens new opportunities for further enhancing nanoscale light–matter interactions to benefit numerous areas such as nonlinear optics, nanolasers, plasmonic hot carrier technology, and surface-enhanced Raman and infrared absorption spectroscopies. [ABSTRACT FROM AUTHOR]

In this article, a multiband, planar, direct energy rectification, and dual polarized infrared plasmonic nanoantenna is presented and numerically simulated using finite element method (FEM). Broadband characteristics are highly suitable for energy harvesting applications. The proposed nanoantenna structure comprises cross bowtie aluminum structures deposited on the silicon dioxide (SiO2) substrate. In the proposed device, incoming thermal electromagnetic energy is first enhanced by micro-lenses through focusing the thermal energy onto the nanoantenna. Then, further enhancement is achieved using several nanoantennas, each with different resonance length, to achieve enough electrical field for electron field emission from sharp metallic tips in their gaps. Each nanoantenna resonates in the proper wavelength, electrical field is enhanced in the gap, and finally, a total current is generated from electron field emissions. The calculated current, based on Fowler-Nordheim theory, matches well with the simulation results. The total current of the proposed nanostructure is superposition of the produced current of each nanoantenna. To our best knowledge, this is the first report on a multiband nanostructure for energy harvesting. As a typical implementation, a structure is designed for energy absorption in the mid infrared wavelengths, 1-4 µm. [ABSTRACT FROM AUTHOR]

The theory of characteristic modes (TCMs) based on the surface integral equation (SIE) formalism is presented for the analysis of plasmonic nanostructures. With TCM, excitation-independent characteristic solutions of the underlying electromagnetic field problem are obtained. Both single and multiple particle nanostructures are analyzed using the conventional SIE approach and the TCM formalism. By comparing these results, the modes that are responsible of the observed scattering and absorption characteristics can be identified. These solutions can be further utilized in the design and tuning nanoantenna configurations for specific application purposes. [ABSTRACT FROM PUBLISHER]

We have investigated numerically a narrowband near unity mid-infrared absorber based on a periodic array of gold split cross antenna backed by a dielectric spacer and a gold backmirror. We systematically studied the spectral dependence on the antenna parameters and explored the optimized parameters for nanofabrication. The optimized structure has a linewidth of 39 nm at 3.17 µm and the peak absorption is 96.5%. This can be explained in terms of surface lattice resonance of the periodic structure. The investigated structure can be devised as a mid-infrared refractive index sensor. Due to the strong near field enhancement and spectral dependence on the surface dielectric conditions, the narrow linewidth arises from the coupled plasmonic-photonic modes in the structure and has potential applications in plasmonic biosensing. [ABSTRACT FROM AUTHOR]

A very electrically small, active open cylindrical coated nanoparticle model is constructed, and its electromagnetic properties are investigated in the visible frequency band. Its optical response under both planewave and electric dipole antenna excitations shows very strong dipole behavior at its lowest resonance frequency. The scattering cross section at that dipole resonance frequency is increased by more than +50 dBsm for the planewave excitation. When the open structure is excited by a small current (I0 = 1 ×10-3A) driven dipole antenna, the maximum radiated power of the composite nanoantenna can be increased by +83.35 dB over its value obtained when the dipole antenna radiates alone in free space. The behaviors under various locations and orientations of the dipole are explored. Dipole orientations along the cylinder axis and symmetric locations of the dipole produced the largest radiated power enhancements.

We present a theoretical framework, based on plasmonic circuit models, for generating a multiresonant field intensity enhancement spectrum at a single "hot spot" in a plasmonic device. We introduce a circuit model, consisting of an array of coupled LC resonators, that directs current asymmetrically in the array, and we show that this circuit can funnel energy efficiently from each resonance to a single element. We implement the circuit model in a plasmonic nanostructure consisting of a series of metal bars of differing length, with nearest neighbor metal bars strongly coupled electromagnetically through air gaps. The resulting nanostructure resonantly traps different wavelengths of incident light in separate gap regions, yet it funnels the energy of different resonances to a common location, which is consistent with our circuit model. Our work is important for a number of applications of plasmonic nanoantennas in spectroscopy, such as in single-molecule fluorescence spectroscopy or Raman spectroscopy. [ABSTRACT FROM AUTHOR]

The near-field optical interaction of a nanohole dimer milled in a gold film and illuminated by an optical plane-wave is investigated. Depending on the polarization direction of the incident light, two resonant peaks are generated, in the normalized transmission spectrum due to the strong interaction between the nanoholes. In order to elucidate the nature of the interaction between the nanohole dimer elements at the resonant peaks, the symmetry breaking idea is applied. It is found that, in contrast to the complementary metallic nanoparticle dimers, the short and long wavelength peaks of the transmission spectrum can be assigned to in-phase and out-of-phase interaction of two adjacent magnetic dipoles, respectively. Furthermore, it is shown that breaking the symmetry in line with the polarization of the incident magnetic field results in severely antiphase interaction, while breaking the symmetry in line with the polarization of the incident electric field results in slightly out-of-phase interaction, at the long wavelength peak. The numerical simulation results are verified with Magnetic Coupled Dipole Approximation (MCDA) method. [ABSTRACT FROM AUTHOR]

Two-dimensional metamaterials support both plasmonic and coupled lattice (Fano) resonant modes that together could enhance optoelectronics. Descriptions for plasmon excitation in Fano resonant lattices in non-vacuum environments typically use idealized, homogeneous matrices due to computational expense and limitations of common approaches. This work described both localized and coupled resonance activity of two-dimensional, square lattices of gold (Au) nanospheres (NS) in discontinuous, complex dielectric media using compact synthesis of discrete and coupled dipole approximations. This multi-scale approach supported attribution of experimentally observed spectral resonance energy and bandwidth to interactions between metal and dielectric substrate(s) supporting the lattices. Effective polarizabilities of single AuNS, either in vacuo or supported by glass and/or indium tin oxide (ITO) substrates, were obtained with discrete dipole approximation (DDA). This showed plasmon energy transport varied with type of substrate: glass increased scattering, while ITO increased absorption and energy confinement. Far-field lattice interactions between AuNS with/without substrates were computed by coupled dipole approximation (CDA) using effective polarizabilities. This showed glass enhanced diffractive features (e.g., coupled lattice resonance), while ITO supported plasmon modes. This compact, multiscale approach to describe metasurfaces in complex environments could accelerate their development and application. [ABSTRACT FROM AUTHOR]

In this paper, a novel optical nanoantenna based on two-dimensional plasmonic nano-ring antenna array is proposed, investigated numerically and compared with a nano-disk antenna array. The results show that the nano-ring structure has resonances similar to the resonances of nano-disk structure but in higher wavelengths. These resonances are tunable by varying the structural parameters of the ring. The optical properties of the proposed structure are investigated in the context of designing a plasmonic refractive index sensor. The nano-ring antenna array sensor has large sensitivity in comparison to the conventional nano-disk antenna arrays. The special feature of the presented structure and the device concepts introduced in this work are applicable in realization of various integrated components and could play an important role in development of plasmonic sensors. [ABSTRACT FROM AUTHOR]

Plasmonic metal nanostructures have recently attracted extensive research and developed into a promise approach for enhancing the performance of various optoelectronic devices. This brief article reviews recent research advances on the plasmonic enhanced optoelectronic devices and highlights a variety of strategies of incorporating plasmonic nanostructures into different optoelectronics such as solar cells, light-emitting diode, and multicolor photodetector, etc. In addition, the benefits of using various plasmonic metal nanostructures are discussed and the resulting enhancement mechanisms are displayed and summarized. [ABSTRACT FROM AUTHOR]

Here, we observed the local angular chiroptical effects with unidirectional emission based on exquisitely designed plasmonic nanopillar antennas. Firstly, the scattering spectra for the asymmetric nanoantennas show double resonant peaks when illuminated by circular polarized light. The calculated circular dichroism reaches the maximum value at one resonant peak while almost disappears at the other peak. Secondly, when we turn to the momentum space for the CD-disappeared peak, the asymmetric nanoantennas exhibit different angular emission patterns that are sensitive to the handedness of light, which indicate the existence of the local angular chiroptical effects. The emission patterns also show unidirectional emission lobes in momentum space, which is distinct to other chiral phenomenon. Multipolar expansion and Green's function method in stratified medium is used to demonstrate the inner mechanism of the observed local angular chiroptical effects, and we found the phase difference of the multipolar resonance is the origin of the distinct local angular chiroptical effects. Our work investigating the local angular chiroptical effects based on nanopillar will shed new light on optical chirality and will be widely applied to wavelength router, photon-detection, and other optoelectronic devices. • In this study, we designed an optcial antenna based on plasmonic nanopillar for extrinsic chiroptical effects. • Generally, spectral responses are the common research point for the chiroptical effects. Here, we investigate chiroptical effects in the creative perspective of momentum space. Through the traditional spectral responses, there seems no chiroptical effects for the designed optical antennas. However, when turn to the angular emission patterns in momentum space, the designed antenna shows gigantic extrinsic chirality in momentum space accompanied by unidirectional emission lobes toward to the totally different direction. • Our study on extrinsic chiroptical effects in moment space provides a novel perspective to understand chirality and shed a new light for biosensing and chiral photon detection. [ABSTRACT FROM AUTHOR]

In this letter, we experimentally demonstrate, by integrating plasmonic nanoantennas, that membrane-based micromechanical resonators can become infrared (IR) active. The photo-thermomechanical effect induced by nanoantennas enables actuation of mechanical structures. Using this hybrid nanoantenna coupled mechanical device as a thermal IR detector, we achieved a current responsivity of 12 mA/W corresponding to a displacement responsivity of 98.7 μm/W and a thermal time constant of 5.7 ms at a wavelength of 6 μm. This approach can be extended to any mechanical resonator for new optomechanical sensing modalities. [ABSTRACT FROM PUBLISHER]

Abstract: Damping rates of multipolar, localized surface plasmons (SPs) of gold and silver nanospheres of radii up to 1000nm were found with the tools of classical electrodynamics. The significant increase in damping rates followed by noteworthy decrease for larger particles takes place along with substantial red-shift of plasmon resonance frequencies as a function of particle size. We also introduced interface damping into our modeling, which substantially modifies the plasmon damping rates of smaller particles. We demonstrate unexpected reduction of the multipolar SP damping rates in certain size ranges. This effect can be explained by the suppression of the nonradiative decay channel as a result of the lost competition with the radiative channel. We show that experimental dipole damping rates [H. Baida, et al., Nano Lett. 9(10) (2009) 3463, and C. Sönnichsen, et al., Phys. Rev. Lett. 88 (2002) 077402], and the resulting resonance quality factors can be described in a consistent and straightforward way within our modeling extended to particle sizes still unavailable experimentally. [Copyright &y& Elsevier]

The nonradiative decay of a localized surface plasmon through absorption of a captured photon and excitation of an energetic electron–hole pair is a potentially very effective way to enhance chemical reactions on metal nanoparticle surfaces, so far limited to Ag (and Au). Here we explore the possibility of efficient and spectrally widely tunable optical absorption engineering based on heterometallic optical nanoantennas. They consist of an optimized antenna element made of Au (or Ag) and a catalytically active second metallic element separated by a thin SiO2 layer. Specifically, we find that stacked Au–SiO2–Pd nanodisk antennas exhibit pronounced local absorption enhancement in the catalytic Pd particle. The effect is caused by efficient power transfer from the Au disk, exhibiting a narrow low-loss resonance and acting as an antenna collecting photons, to the Pd disk due to strong coupling between the two. The Pd element thus acts as receiver that efficiently dissipates energy into electron–hole pairs owing to efficient coupling to intra and interband transitions. In fact, the energy transfer is found to be so effective that the absorption efficiency at a given wavelength can be enhanced up to 6 to 9 times, and the total absorption integrated over a wide spectral range (400–900 nm) up to 2-fold, depending on the antenna dimensions. This finding suggests a novel route toward highly efficient plasmon-enhanced catalysis on widely selectable catalytic metal particle surfaces not limited to the "classic" plasmonic metals Au and Ag. [ABSTRACT FROM AUTHOR]

A nanoplasmonic "transceiver" was assembled to examine the efficiency of coupled plasmonic antennas and their resonance interactions. In particular, plasmonic focusing receiver antenna coupled to transmitting annular antenna having a short central plasmonic wire was measured. The receiver collected incoming radially polarized light and efficiently focused and coupled it to a rear side transmitter comprised of a short resonant plasmonic wire and annular aperture. Transmission spectra exhibited a substantial signature of the wire Fabry−Perot resonances. The wire antenna crossection was improved by nearly 3 orders of magnitude by the focusing antenna system. [ABSTRACT FROM AUTHOR]