Yagi-Uda Nanoantenna Research Articles

Electrically driven nanoantenna metasurface for coherent thermal emission

Nanoantennas and their arrays (metasurfaces) provide a versatile platform for controlling the coherence of thermal emission. Conventional designs rely on global heating, which impedes emission efficiency and on-chip integration. In this work, we propose an electrically driven metasurface composed of a Yagi-Uda nanoantenna array interconnected by S-shaped electrode wires, which enables the concurrent manipulation of thermal emission spectrally and directionally. A direct simulation approach based on the Wiener-chaos expansion method is employed for quantitative analysis. Our metasurface device exhibits a narrowband emission with high directivity, which is one order higher than that of a single nanorod antenna case. The modeling framework established in this work opens a promising route for realizing coherent mid-infrared emission by metasurfaces.

Bowtie nanoantenna driven by a Yagi-Uda nanoantenna: a device for plasmon-enhanced light matter interactions

We propose a plasmonic device, based on the combination of a Yagi-Uda nanoantenna and a bowtie nanoantenna, that can enable on-chip implementation of plasmon-enhanced light-matter interaction processes such as surface-enhanced Raman scattering (SERS), surface-enhanced infrared absorption spectroscopy, and plasmon-enhanced fluorescence. In this device, a localized source is employed to excite the Yagi-Uda nanoantenna, which in turn drives the bowtie nanoantenna. We employ finite difference time domain (FDTD) method to perform numerical simulations to obtain radiation characteristics of the Yagi-Uda nanoantenna as well as the electric field enhancements in the vicinity of the bowtie nanoantenna excited by the Yagi-Uda nanoantenna. We find that for a wavelength of 785 nm, an electric field enhancement of ∼ 196 can be achieved in between the arms of the bow-tie nanoantenna even when the minimum gap between nanostructures is as large as 10 nm. It is found that this electric field enhancement is significantly large when compared with the maximum electric field enhancement (∼ 11) obtained for direct excitation of the bowtie nanoantenna by a point source or with the maximum electric field enhancement (∼ 34) obtained for plane wave excitation of the bowtie nanoantenna. As the electromagnetic enhancement of SERS can be approximated to be the fourth power of the electric field enhancement, SERS electromagnetic enhancement of ∼ 1.5 × 109 is achieved for the bow-tie nanoantennas excited by the Yagi-Uda nanoantennas, even when the minimum gap between the arms of the bow-tie nanoantenna is as large as 10 nm. We also analyze the effect of various geometrical parameters of the nanoantennas and show that the maximum electric field enhancement at a given wavelength can only be obtained when both the Yagi-Uda nanoantenna and the bowtie nanoantenna are resonant at that wavelength. Moreover, we calculate the electric field enhancements at different near-infrared wavelengths. Employing the proposed device, an electric field enhancement of ∼ 945 is obtained at a wavelength of 1500 nm resulting in a SERS electromagnetic enhancement factor as high as ∼ 8 × 1011, even when the minimum gap between nanostructures is as large as 10 nm.

Optimization of Modified Yagi-Uda Nanoantenna Arrays Using Adaptive Fuzzy GAPSO

This paper presents an optimization of the radiation and absorption characteristics of modified Yagi-Uda (YU) nanoantenna arrays. Four geometries of antennas are considered: conventional YU fed by voltage source and transmission line, and YU with a loop element fed by voltage source and transmission line. The numerical electromagnetic simulations of these nanoantennas were made by the method of moments (MoM). The optimization method used is the adaptive fuzzy GAPSO, which consists of hybridization between genetic algorithm (GA) and particle swarm optimization (PSO), with a fuzzy system employed to adapt the inertial weight ω and the acceleration coefficients C1 and C2 of PSO. The optimized results show that the modified YU nanoantennas present better characteristics of gain, directivity, and radiation efficiency than the conventional YU antenna.

Hybrid thermal Yagi-Uda nanoantennas for directional and narrow band long-wavelength IR radiation sources.

We investigate the possibility of spatially and spectrally controlling the thermal infrared emission by exploitation of the Yagi-Uda antenna design. Hybrid antennas composed of both SiC and Au rods are considered and the contributions of emission from all the elements, at a given equilibrium temperature, are taken into account. We show that the detrimental effect due to thermal emission from the not ideal parasitic elements drastically affect the performances of conventional thermal Au antennas in the 12 µm wavelength range. Nevertheless, our results show that the hybrid approach allows the development of efficient narrow-band and high directivity sources. The possibility of exploiting the Yagi-Uda design both in transmission and in reception modes, may open the way to the realization of miniaturized, efficient, robust and cheap sensor devices for mass-market applications.

Performance enhancement of thin-film solar cell using Yagi–Uda nanoantenna array embedded inside the anti-reflection coating

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.

Surface plasmons manipulated Smith-Purcell radiation on Yagi-Uda nanoantenna arrays.

An electron bunch (e-bunch) passing through an insulator-metal-insulator (IMI) substrate can excite surface plasmons (SPs) on the substrate. Recent studies demonstrate that Smith-Purcell radiation (SPR) from one-dimensional gratings on an IMI substrate can be manipulated and enhanced by e-bunch excited SPs. However, under this configuration, only the emission along the direction of electron moving can be controlled. To steer both the azimuthal and polar angles of the far-field emission pattern requires other mechanisms. In this work, the SP-manipulated SPR with a Yagi-Uda nanoantenna (YUNA) array on an IMI substrate for generation of light beams with designed far-field patterns is proposed and explored by computer simulations. Emission of SPR along and perpendicular to the direction of electron movement can be manipulated by designing grating period and YUNA structure, respectively. Dependence of the azimuthal and polar angles of emitted light beam on geometry parameters of feed and directors of YUNA are elucidated. Furthermore, emission of multiple beams containing a single wavelength and multiple wavelengths with required far-field angles can be achieved using different groups of YUNA arrays on different IMI substrates. The proposed mechanism may have applications for light sources, optical imaging, optical beam steering, holography, microdisplay and cryptography.

Steerable plasmonic nanoantennas: active steering of radiation patterns using phase change materials.

In this article, we describe active steering of radiation patterns by complex nanoantenna structures - called steerable nanoantennas (SNs) - formed by combining multiple Yagi-Uda nanoantennas and thin films of a phase change material (VO2). The radiation patterns of these nanoantennas can be actively steered by tunably changing the phase of the VO2 thin films from the semiconductor phase to the metallic phase. Moreover, the nanoantennas enable steering of the radiation patterns 'in the plane' of the nanoantennas. We demonstrate that the radiation pattern's maximum achievable steering is 90° for a two-element steerable nanoantenna when the phase of the VO2 thin film is changed from the semiconductor phase to the metallic phase. Moreover, it was observed that the radiation pattern of the steerable nanoantennas being proposed in our paper can be designed to be much more directed than previously reported steerable nanoantennas. By employing a four element steerable nanoantenna, we also demonstrate a full 360° active steering of the radiation pattern. This steerable nanoantenna consists of four coplanar Yagi-Uda nanoantennas, with each Yagi-Uda nanoantenna being present inside a VO2 thin film but each individually addressable VO2 thin film being separated from the other VO2 films by an air gap. We demonstrate that the radiation pattern can be tunably steered in 12 different directions using this four element steerable nanoantenna depending on the states of the four VO2 thin films. The steerable nanoantennas can find applications in areas such as tunable on chip plasmonic interconnects, networks on chip, or for selective excitation of fluorophores on a sensor chip.

Effect of Yagi–Uda nano-antenna element shape on the directivity and radiation efficiency

In this paper, different optimal designs of Yagi–Uda nano-antennas (NAs) are introduced and analyzed based on different element shapes to maximize the directivity and radiation efficiency. The studied element shapes include triangular, hexagonal, cube, square, rotated square, rectangular, ellipsoid, and elliptical cylinder shapes. The NAs parameters for each design are optimized using particle swarm optimization algorithm to achieve high directivity at a wavelength of 500 nm for wireless point-to-point applications. The designs are numerically analysed using 3-D finite difference time domain method (3-D FDTD) via Lumerical software package. To illustrate the performance of the proposed antennas, different radiation parameters such as radiation pattern, directivity, and radiation efficiency have been studied. Moreover, a tolerance of ± 5% is calculated to consider the imperfections that may appear in the fabrication process at a nanoscale. The optimized rectangular prism NA achieves the highest directivity of 24.21 with an efficiency of 50.74%. However, the optimized triangular prism NA has the highest efficiency of 73% with a directivity of 20.89. This enhancement is mainly attributed to the efficient coupling between array elements along with low side lobe level. However, a trade-off between directivity and radiation efficiency is obtained by the hexagonal prism NA with directivity of 21.9 and radiation efficiency of 69.1%.

Optical Interaction Effects in Nanoplasmonic Antennas at Visible Wavelengths

In this article we study the effects of nanoelements’ optical interactions on the properties and response of the nanoplasmonic antennas. Here, we report on some simple, ultra directive, and compact optical antenna designs working based on a hybridized plasmon mode. By enhancing the electromagnetic (EM) coupling between the nanoparticles, we achieve new optimum designs. Using two, three, or four closed nanoelements, the nano-antenna shows high directionality and gives us the opportunity to have a compact, color-switched, and spectrally-tunable optical nanoantenna. Such design are experimentally realized by HCL – a bottom-up nanofabrication based on colloidal self-assembly. Finally, in order to design a highly directive nanoantenna we present a new highly directive and packed Yagi-Uda (P-YU) nano-antenna.

Photoluminescence-Driven Broadband Transmitting Directional Optical Nanoantennas.

Optical nanoantennas mediate near and far optical fields. Operating a directional nanoantenna in transmitting mode is challenging because the antenna needs to be driven by a nanosized optical frequency generator, which must work at the antenna's resonance frequency and be precisely attached to the antenna's feed with correct polarization. Quantum emitters have been used as optical nanogenerators, but their precise positioning relative to the nanoantenna is technically challenging, setting up a barrier to the practical implementation. One unique source to drive nanoantenna is the photoluminescence from the material of the nanoantenna because the high operational frequency of the antenna reaches the regime for the electronic transitions in matter. Here, we exploit plasmon-modulated photoluminescence (PMPL) as an effective optical source to drive directional nanoantennas. We experimentally realize two technically challenging theoretical proposals, namely, an optical nanospectrometer based on Yagi-Uda nanoantennas and tunable broadband directional emission from log-periodic nanoantennas. Using photoluminescence from the nanoantenna as an optical source promotes practical implementation of transmitting optical nanoantennas.

Packed Yagi-Uda nano-antennas using a unidirectional feed at visible wavelengths.

Optical nano-antennas' capability for controlling the intensity and direction of freely propagating waves is a precursor to demanding on-chip optical communications. Here we present a novel and efficiently packed Yagi-Uda (P-YU) nano-antenna which is dramatically directive and shortened. This is due to the excitation of a pair of strong interacting Au nanorods as a feed in the form of conventional Yagi-Uda (YU). Using a sophisticated feed with a unidirectional radiation pattern in a wavelength close to the antiphase hybridized plasmon causes significant directionality in the designed nano-antennas' emission. This allows us to reduce the number of directors or overall size while directivity and gain of the P-YU antenna considerably improve at about 610nm.

Core-shell Yagi-Uda nanoantenna for highly efficient and directive emission

We study radiation from hybrid Yagi-Uda nanoantennas composed of metal-dielectric core-shell nanoparticles. We show that due to the presence of two types of resonances in each particle at close frequencies the hybrid Yagi-Uda nanoantenna can operate in two different regimes. In the first regime at low frequencies it operates similarly to plasmonic and all-dielectric Yagi-Uda nanoantennas, and it is characterized with highly directive emission in a forward direction. In the second regime at higher frequencies the hybrid nanoantenna can emit with a high directivity in backward direction due to the presence of the hybrid dispersion branch with negative group velocity. Moreover by choosing the appropriate nanoantenna parameters one can achieve the operation regime when due to excitation of dark magnetic dipole modes in nanoantenna high values of directivity and Purcell factor are realized simultaneouslly in extremely narrow frequency range.

Dielectric Yagi-Uda nanoantennas driven by electron-hole plasma photoexcitation

All-dielectric nanophotonics based on high-index dielectric nanoparticles became a powerful platform for modern light science, providing many fascinating applications, including high-efficient nanoantennas and metamaterials. High-index dielectric nanostructures are of a special interest for nonlinear nanophotonics, where they demonstrate special types of optical nonlinearity, such as electron-hole plasma photoexcitation, which are not inherent to plasmonic nanostructures. Here, we propose a novel type of highly tunable all-dielectric Yagi-Uda nanoantennas, consisting of a chain of Si nanoparticles exciting by an electric dipole source, which allow tuning of their radiating properties via electron-hole plasma photoexcitation. We theoretically and numerically demonstrate the tuning of radiation power patterns and the Purcell effect by additional pumping of several boundary nanoparticles with relatively low peak intensities of fs-laser.

Yagi–Uda nanoantenna For NIR domain

Single component metal nanoparticles, such as Ag and Au, have surface plasmon resonance wavelengths in the visible region having a weak dependence on particle size. For double component (core/shell) nanoparticles, by proper tuning the core size and shell thickness, a wide variation in optical radiation characteristics as well as in surface plasmon resonance wavelength up to Near-Infrared (NIR) region can be achieved. These aspects encourage one to model an optical Yagi–Uda antenna adopting core/shell nanoparticles as feed element, reflector and directors. In this paper, adopting the COMSOL Multiphysics software, we design all core/shell Yagi–Uda nanoantennas in the NIR domain. $$\hbox {SiO}_{2}/\hbox {Au}$$ core/shell nanoparticles are taken as antenna elements for the proposed antenna, whose surface plasmon resonance wavelength can be shifted to the NIR region by tuning the core to shell size ratio in a particular size band. The optimized directivity and gain for this antenna is achieved with only one reflector and one director, thus making it ultra-compact, cost-effective and simple in structure. This type of very highly directional Yagi–Uda nanoantenna can be used in medical science such as in targeted drug delivery and in wireless optical communication.

Super directive Yagi–Uda nanoantennas with an ellipsoid reflector for optimal radiation emission

In this paper, the optimal designs of silicon Yagi–Uda nanoantennas (NAs) with an ellipsoid reflector have been proposed and analyzed using the 3D finite-difference time-domain method. The combination of nanospheres, nanowires, and ellipsoid reflectors has been employed to enhance the antenna directivity. The nanoantenna geometrical parameters are optimized using the particle swarm optimization algorithm. The optimized spherical NA with an ellipsoid reflector shows high directivity of 19.89, which is higher than the conventional counterpart by 65.75%. This enhancement is attributed to the different supported modes by the ellipsoid reflector, which increases the forward radiation and suppresses the backward one. Further, the optimized nanowire design with an ellipsoid reflector has achieved a directivity of 23.4. In addition, the radiation efficiency has been increased to 80.2% and 75.9% for optimized spherical and nanowire antennas, respectively. This enhancement is attributed to the efficient coupling between array elements as well as reduced sidelobe and back-lobe levels.

Dynamically reconfigurable metal-semiconductor Yagi-Uda nanoantenna

We propose a novel type of tunable Yagi-Uda nanoantenna composed of metal-dielectric (Ag-Ge) core-shell nanoparticles. We show that, due to the combination of two types of resonances in each nanoparticle, such hybrid Yagi-Uda nanoantenna can operate in two different regimes. Besides the conventional nonresonant operation regime at low frequencies, characterized by highly directive emission in the forward direction, there is another one at higher frequencies caused by hybrid magneto-electric response of the core-shell nanoparticles. This regime is based on the excitation of the van Hove singularity, and emission in this regime is accompanied by high values of directivity and Purcell factor within the same narrow frequency range. Our analysis reveals the possibility of flexible dynamical tuning of the hybrid nanoantenna emission pattern via electron-hole plasma excitation by 100 femtosecond pump pulse with relatively low peak intensities $\sim$200 MW/cm$^2$.

Highly Directive Hybrid Yagi-Uda Nanoantenna for Radition Emission Enhancement

In this paper, a novel design of Yagi–Uda nanoantenna is introduced and numerically analyzed using finite integration technique via computer simulation technology software. The proposed nanoantenna consists of five core-shell nanowires with silicon cladding and silver core to achieve high directivity for wireless point to point applications. The proposed design shows a high directivity of 17.21 at a wavelength of 500 nm, which exceeds the spherical dielectric counterparts with directivity of 12. Therefore, an enhancement of 43.41% is achieved, which is mainly useful for spontaneous emission manipulation and photon detection. This enhancement is attributed to the silicon dielectric shell that exhibits magnetic mode with high refractive index, as well as the surface plasmon mode supported by the silver core. Additionally, the proposed cylindrical design has advantages in terms of high homogeneity of the field distribution, which overcomes the inhomogeneity field distribution of the nanosphere-based design.

Compact Nonlinear Yagi-Uda Nanoantennas.

Nanoantennas have demonstrated unprecedented capabilities for manipulating the intensity and direction of light emission over a broad frequency range. The directional beam steering offered by nanoantennas has important applications in areas including microscopy, spectroscopy, quantum computing, and on-chip optical communication. Although both the physical principles and experimental realizations of directional linear nanoantennas has become increasingly mature, angular control of nonlinear radiation using nanoantennas has not been explored yet. Here we propose a novel concept of nonlinear Yagi-Uda nanoantenna to direct second harmonic radiation from a metallic nanosphere. By carefully tuning the spacing and dimensions of two lossless dielectric elements, which function respectively as a compact director and reflector, the second harmonic radiation is deflected 90 degrees with reference to the incident light (pump) direction. This abnormal light-bending phenomenon is due to the constructive and destructive interference between the second harmonic radiation governed by a special selection rule and the induced electric dipolar and magnetic quadrupolar radiation from the two dielectric antenna elements. Simultaneous spectral and spatial isolation of scattered second harmonic waves from incident fundamental waves pave a new way towards nonlinear signal detection and sensing.

Radiation-enhanced optical antenna based on nonperiodic metallic nanoparticle dimer chain

With the aid of multi-sphere dyadic Green's function, we present a design of optical nanoantenna which is composed of a nonperiodic nanoparticle dimer chain. By breaking the periodicity of the dimer chain, the radiative emission of the dimer chain is significantly enhanced because the strong coupling which limits radiation enhancement is inhibited when the separations between dimers are reduced. Our work clearly shows the crucial role of nonperiodicity in the design of the Yagi-Uda nanoantenna.

Enhancing Weak Optical Signals Using a Plasmonic Yagi—Uda Nanoantenna Array

Nanoantennas have been used in a wide range of applications in sensing, spectroscopy, and imaging-in general, the antennas can enhance physical phenomena such as the local electric field or concentrate light in a certain direction. We have fabricated an array of 80 plasmonic Yagi-Uda nanoantennas on the cladding of an optical fiber and, by doing this, we show that the signal reaching the fast detector can be increased by a factor of 5 dB. The experiment demonstrates that plasmonic directive nanoantennas can indeed collect and concentrate electromagnetic radiation along a certain direction and eventually could be used to enhance weak signals.