Nanopatch Antennas Research Articles

Förster Resonance Energy Transfer Rate and Efficiency in Plasmonic Nanopatch Antennas

AbstractSuccessful control of Förster resonance energy transfer (FRET) through the engineering of the local density of optical states (LDOS) will allow us to develop novel strategies to fully exploit this phenomenon in key enabling technologies. Here we present an experimental and theoretical study on the effect of the LDOS on the FRET rate and efficiency in plasmonic nanopatch antennas formed between a gold nanoparticle and an extended silver film. Our results reveal that plasmonic nanopatch antennas of similar levels of LDOS exhibit comparable levels of FRET rate and FRET efficiency, demonstrating that LDOS plays an important part in controlling both FRET rate and efficiency. Our findings contribute to the ongoing debate about the relation between the FRET process and the LDOS, as well as directly impacting the development of novel FRET based light harvesting and sensing devices.

Liquid-Metal-Based Nanophotonic Structures for High-Performance SEIRA Sensing.

Surface-enhanced infrared absorption (SEIRA) spectroscopy can provide label-free, nondestructive detection and identification of analytes with high sensitivity and specificity, and therefore has been widely used for various sensing applications. SEIRA sensors usually employ resonant nanophotonic structures, which can substantially enhance the electric field and hence light-matter interactions by orders of magnitude in certain nanoscale hot spots of the devices. However, as ever, smaller hot spots are employed to further enhance the field, the delivery of analytes into such hot spots becomes increasingly challenging. Here, high-performance nanophotonic SEIRA sensors based on nanopatch antennas with a liquid gallium ground plane are demonstrated, which not only lead to ultrahigh field confinement and enhancement, but also allow for convenient and efficient delivery of analytes into nanometric hot spots by employing a simple procedure suitable for point-of-care applications. The sensors exhibit superior sensitivity in the midinfrared spectral region. Around 10% molecular vibrational signals (i.e., the modulation of a sensor's reflection spectrum owing to the molecular vibrational modes of the analytes) near 2900cm-1 are achieved from sensing monolayer 1-octadecanethiol. This cost-effective and reliable method for realizing liquid-metal-based nanophotonic structures provides a new strategy for developing high-performance sensors and other photonics applications in the infrared region.

Optical properties of new hybrid nanoantenna in submicron cavity

An essential area of nanophotonics is the creation of efficient quantum emitters operating at high frequencies. In this regard, plasmon nanoantennas based on nanoparticles on metal (nanopatch antennas) are incredibly relevant. We have created and investigated a new hybrid nanoantenna with a cube on metal and quantum emitters. We demonstrate an increase up to 60 times for the rate of spontaneous emission and the gap-plasmon mode changing for nanopatch antenna in the metallic well. The results show the possibility of creating plasmon antennas in a controlled way by creating an array of regularly arranged nanoscale cavities-resonators.

Near-field imaging of plasmonic nanopatch antennas with integrated semiconductor quantum dots

Plasmonic nanopatch antennas that incorporate dielectric gaps hundreds of picometers to several nanometers thick have drawn increasing attention over the past decade because they confine electromagnetic fields to grossly sub-diffraction-limited volumes. Substantial control over the optical properties of excitons and color centers confined within these plasmonic cavities has already been demonstrated with far-field optical spectroscopies, but near-field optical spectroscopies are essential for an improved understanding of the plasmon–emitter interaction at the nanoscale. Here, we characterize the intensity and phase-resolved plasmonic response of isolated nanopatch antennas by cathodoluminescence microscopy. Furthermore, we explore the distinction between optical and electron beam spectroscopies of coupled plasmon–exciton heterostructures to identify constraints and opportunities for future nanoscale characterization and control of hybrid nanophotonic structures. While we observe substantial Purcell enhancement in time-resolved photoluminescence spectroscopies, negligible Purcell enhancement is observed in cathodoluminescence spectroscopies of hybrid nanophotonic structures. The substantial differences in measured Purcell enhancement for electron beam and laser excitation can be understood as a result of the different selection rules for these complementary experiments. These results provide a fundamentally new understanding of near-field plasmon–exciton interactions in nanopatch antennas, which is essential for myriad emerging quantum photonic devices.

Tunable graphene nanopatch antenna design for on-chip integrated terahertz detector arrays with potential application in cancer imaging.

Aim: Further to our reports on chip-integrable uncooled terahertz microbolometer arrays, compatible with medium-scale semiconductor device fabrication processes, the possibility of the development of chip-integrable medical device is proposed here. Methods: The concept of graphene-based nanopatch antennas with design optimization by the finite element method (FEM) is explored. The high-frequency structure simulator (HFSS) utilized fine FEM solver for analyzing empirical mode decomposition preprocessing and for modeling and simulating graphene antennas. Results: Graphene nanopatch antennas exhibited tunable features with varying patch dimensions and dependence on substrate material permittivity. Conclusion: This work implements reconfigurable graphene nanopatch antenna compatible with terahertz microbolometer arrays. This design concept further developson-chip medical devices for possible screening of cancer cell with terahertz image processing.

Low-loss, centimeter-scale plasmonic metasurface for ultrafast optoelectronics

Plasmonics can dramatically improve the radiative properties of fluorescent materials by precisely tailoring the local density of states, but has largely been dismissed for practical optoelectronic applications due to losses and lack of scalability to macroscopic areas. Here, we demonstrate a low-loss plasmonic metasurface that can collect fast-modulated light with a 3 dB bandwidth exceeding 14 GHz and a 120º acceptance angle and convert it to a directional source with, to the best of our knowledge, a record-high overall efficiency of ∼ 30 % . This large-area metasurface composed of fluorescent dye coupled to nanopatch antennas, exhibits a 910-fold increase in the overall fluorescence and a 133-fold emission rate enhancement—values previously only observable for isolated, highly optimized single nanostructures. Critical for future applications ranging from optoelectronics to biosensing, this metasurface was created over macroscopic areas with scalable techniques and the performance was validated over centimeter-scale regions. In particular, we believe this approach shows promise for the burgeoning field of visible/near-infrared wireless communications, where radical new designs and materials are needed for ultrafast, efficient, omnidirectional detectors and incoherent sources.

Design and Analysis of Plasmonic Antenna for Nanoscale Wireless Applications

The paper demonstrates design and analysis of plasmonic antenna for nanoscale wireless links. A surface plasmon polarities (SPP’s) based Hybrid Metal Insulator Metal (HMIM) based circular nano patch antenna for optical frequencies are designed and analysed using commercially available CST Microwave studio suite. The proposed circular patch antenna operated in the optical frequency band of 225 THz to 245 THz with a bandwidth of 20 THz. The overall size of the optical antenna is 1500 x 1000 nm2. The proposed antenna is very much useful in chip scale applications, interconnects and optical sensing applications.

Differential reflectivity spectroscopy on single patch nanoantennas

We present an experimental technique adapted to characterize individual metallic nanostructures in terms of differential reflectivity spectroscopy. We analyze gold patch nanoantennas holding different morphological properties. Our experimental methodology shows steady and reliable results consistent with classical analytical approximations and simulation methods. This technique allows us to identify absorption properties of metallic nanostructures commonly associated with surface plasmon resonances. By contrasting the light absorbed solely by the metallic antenna with respect to a surrounding reference medium, we found that some antennas show absorption of almost 50% of the incident light across the range of the visible spectrum. Plasmonic patch nanoantennas are promising systems in which the confinement of the electromagnetic field inside the dielectric gap strongly modifies the local density of states.

Mode-Matching Enhancement of Second-Harmonic Generation with Plasmonic Nanopatch Antennas.

Plasmonic enhancement of nonlinear optical processes confront severe limitations arising from the strong dispersion of metal susceptibilities and small interaction volumes that hamper the realization of desirable phase-matching-like conditions. Maximizing nonlinear interactions in nanoscale systems require simultaneous excitation of resonant modes that spatially and constructively overlap at all wavelengths involved in the process. Here, we present a hybrid rectangular patch antenna design for optimal second-harmonic generation (SHG) that is characterized by a non-centrosymmetric dielectric/ferroelectric material at the plasmonic hot spot. The optimization of the rectangular patch allows for the independent tuning of various modes of resonances that can be used to enhance the SHG process. We explore the angular dependence of SHG in these hybrid structures and highlight conditions necessary for the maximal SHG efficiency. Furthermore, we propose a novel configuration with a periodically poled ferroelectric layer for an orders-of-magnitude enhanced SHG at normal incidence. Such a platform may enable the development of integrated nanoscale light sources and on-chip frequency converters.

Silver nanoparticle on aluminum mirror: active spectroscopy and decay rate enhancement

Recent advances in nanotechnology and optics have paved the way for new plasmonic devices. One of them are nanopatch antennas that are simple and, at the same time, effective devices for localizing the electromagnetic field on a scale of less than 10 nm and can be used in photonic integrated circuits as effective sources of photons, including single-photon sources. In the present study, we investigate the radiative characteristics of a submonolayer of colloidal CdSe/CdS quantum dots that form island structures in a resonator: a cubic silver nanoparticle on an aluminum mirror. For detecting plasmonic nanoparticles on glass or metal surfaces, we propose a new technique involving a tunable laser and a confocal microscope. We provide a comparative study of the luminescence enhancement factors for QDs in the NPAs upon off-resonance excitation and at a wavelength close to the resonance; a significant difference in the luminescence enhancement factors (by order of magnitude) is demonstrated. A 60-fold reduction in the spontaneous emission time, as well as an increase in the radiation intensity by a factor of 330, has been obtained in the experiments. The increase in the spontaneous emission rate demonstrated for the quantum dots is explained by the Purcell effect. Full-wave simulations of electromagnetic fields were carried out for the model of the developed nanopatch antenna; luminescence enhancement factors and radiative efficiencies were calculated as well.

Design and investigation of a MIMO Nanoantenna operating at optical frequency

Single Patch nanoantenna 300 × 200 × 100 nm3 has been presented. This patch antenna is a multiband antenna, resonating at 387 THz, 509 THz, and 675 THz with bandwidths of 400 GHz, 800 GHz, and 1400 GHz respectively. Based on the patch antenna dimensions, a 4 × 4 MIMO antenna with the Nanometer dimension has been presented in this work. The substrate material used for both the designed antennas is RT/Duroid/6010. The 4 × 4 MIMO nanoantenna, presented, has a size of 1200 × 1200 × 100 nm3. In this MIMO antenna, patches are separated by a distance of λ/2. The performance of the MIMO nanoantenna has been estimated through, Isolation, TARC, Diversity Gain, and ECC. The proposed nanoantenna can be applicable in Optical Communication, Nano-photonics, etc.

Polarization-division and spatial-division shared-aperture nanopatch antenna arrays for wide-angle optical beam scanning.

Chip-based optical beam scanners hold promise for future compact high-speed light detection and ranging (LIDAR) systems. Many of the demonstrated chip-based optical beam scanners are designed based on diffraction-based waveguide gratings as on-chip antennas. The waveguide grating antenna, however, only provides a typical field-of-view (FOV) of roughly 10° by tuning the input light wavelength. In this paper, polarization-division and spatial-division multiplexed nanoantenna arrays are proposed to expand the FOV of on-chip antennas. The proposed device, based on silicon-on-insulator (SOI) platform, consists of three nanoantenna groups which are densely packed and fed by a common silicon nanostrip. It is demonstrated that the combination of the optical mode-multiplexing technique and the antenna engineering allows independent controls over the interactions between multiple nanoantenna groups and the waveguide. By proper engineering of the antenna dimensions, the proposed device achieves a FOV of over 40° within a 100 nm wavelength tuning range, almost tripling that of the conventional waveguide grating antenna.

Optical properties of nanopatch antennas based on plasmonic nanoparticles and ruthenium complex

In this work, a significant reduction (up to 7 ns) of the excited states lifetime of the Ru dye (with a decay time of 850 ns) in an inhomogeneous «aluminium – silver nano-prism system (nano-patch antenna, NPA)», as well as an increase in the photoluminescence emitter to 2-3 times. The increase in the spontaneous emission rate of this substance is caused by the Purcell effect. The Purcell coefficient for the emitter in the cavity with hexagonal silver particles was 120. This decrease in the spontaneous emission decay time in the nano-patch antenna configuration is associated with an increase in the local density of photon states in the plasmon resonator, which increases the probability of a spontaneous transition from the excited state of the emitter. The results obtained by shortening the spontaneous emission time and increasing the intensity of the emitter radiation in a nano-patch antenna show possible prospects for using quantum dots and individual molecules with shorter luminescence times in nano-patch antennas. Such nano-patch antennas can form the basis for creating compact high-speed optical devices. Modeling in the mathematical package Comsol Multiphysics showed that the maximum values of the Purcell factors can exceed 104 in the NPA.

Gap-Plasmon-Enhanced Second-Harmonic Generation in Epsilon-Near-Zero Nanolayers

With the ability to confine light to subwavelength volumes, plasmonic nanostructures and metamaterials have proven to be powerful tools for nanophotonic applications. For nonlinear processes, however, the small dimensions of nanophotonic devices can become problematic, as phase-matching techniques—designed to increase interaction lengths—are no longer applicable. In this work, we utilize the field confining properties of plasmonic nanoparticles in a modified metal-insulator-metal (MIM) patch nanoantenna to efficiently couple to an epsilon near zero (ENZ) mode in a nanolayer film of indium tin oxide (ITO). The modified MIM device differs from traditional MIM structures in that the insulator spacing layer makes use of a low index, 12 nm nanolayer ITO film on top of a higher index SiO2 layer, allowing for highly confined electric fields. Combined with the enhanced nonlinear response at the ENZ point of the ITO film, we are able to achieve second harmonic generation (SHG) enhancements of up to 50,000 relative...

Developer Design of Hybrid Plasmonic Nano Patch Antenna with Metal Insulator Metal Multilayer Construction

Hybrid plasmonic nanopatch antenna with metal-insulator-metal (HMIM) multilayer has been investigated for operation at the frequency of 125–250 THz using the finite element method (FEM) implemented in Ansoft High Frequency Structure Simulator (HFSS). The proposed antenna exhibits a wide bandwidth of 49.5 THz (151.5 THz–201 THz) for the slots thicknesses Wg = 50 nm and Ws = 100 nm and dual bandwidth for Ws = 20 nm. The obtained results show the input impedance of 50.3 Ω input resistance (real part) and 2.3 Ω reactance (imaginary part) occurring at (near) the operation frequency. The maximum gain of 23.98 dB has been observed for resonant frequencies of 176 THz, and the maximum directivity remains above 6.73 dB and 7.46 dB at resonant frequencies of 170 THz and 190 THz, respectively. Our proposed antenna performance is compared to previously reported designs. The copolar and cross-polar radiation patterns are simulated at different resonant frequencies of 160 THz and 197 THz for planes Φ=90° and Φ=0°. The arrays of a proposed antenna are designed in one and two dimensions in order to appropriate high-gain applications.

Surface Plasmon Polaritons Emission with Nanopatch Antennas: Enhancement by Means of Mode Hybridization

We theoretically study the emission of surface plasmon polaritons (SPPs) in cylindrical nanopatch antennas with sub-10 nm dielectric gaps. The eigenmodes of a nanopatch antenna can be classified as...

Nano-Patch Antennas as an Evolution of Optical Antennas

In this paper, we review antennas from the radio wave band to the optical band. The main characteristics of the antennas determining their operation are given. The class of nano-patch antennas (NPA) of the visible and near-infrared ranges is distinguished. The advantage of nano-patch antennas is the good directivity of the antenna radiation and the significant Purcell factor (>102 –103 ), while the technology for creating these antennas is quite simple. The paper also presents various types of photon radiation sources in NPA, among which molecular complexes, quantum dots and color centers in diamonds can be distinguished. On the basis of nano-patch antennas with quantum dots and color centers in nanodiamonds, it is possible to create sources of single photons with picosecond decay rates. The comparison of the characteristics of NPA depending on the shape of plasmon nanoparticles is presented.

Radiative characteristics of nanopatch antennas based on plasmonic nanoparticles of various geometry and tris(2,2’-bipyridine) ruthenium(II) hexafluorophosphate

Effective interaction of light with quantum emitters is important for the development of efficient high-frequency nanophotonic devices. One of the most attractive ways of solving this problem is the employment of nanopatch antennas (NPAs) with various efficient photon emitters. In the present study, we investigated the properties of the NPAs with different geometries involving a [Ru(bpy)3]2+ complex (tris(2,2’-bipyridine) ruthenium(II) hexafluorophosphate) which was taken as a highly stable emitter. An increase in the radiation power of the metalorganic system was experimentally obtained. In particular, an increase in the photoluminescence intensity of the emitter was observed, and a significant reduction (down to 7 ns) in the lifetime of the excited states in the Ru-complex (with ‘free’ lifetime of about 850 ns) was demonstrated for an inhomogeneous ‘aluminum-silver nanoparticle’ system incorporating the Ru-complex. The increase in the spontaneous emission rate of [Ru(bpy)3]2+ was attributed to the Purcell effect. The averaged values of the Purcell factors obtained for the emitter in the resonator with pentagonal and hexagonal silver nanoparticles were 100 and 120, respectively. It was shown that in an NPA with single vertically oriented emitters, the maximum values of the Purcell factors can be as high as 103. Also, radiation patterns were simulated showing that the radiation maximum is observed at an angle of about 50° to the surface of the nanoantenna. Luminescence enhancement factors for the studied types of NPAs were obtained both experimentally and theoretically.

Quasinormal mode solvers for resonators with dispersive materials.

Optical resonators are widely used in modern photonics. Their spectral response and temporal dynamics are fundamentally driven by their natural resonances, the so-called quasinormal modes (QNMs), with complex frequencies. For optical resonators made of dispersive materials, the QNM computation requires solving a nonlinear eigenvalue problem. This raises a difficulty that is only scarcely documented in the literature. We review our recent efforts for implementing efficient and accurate QNM solvers for computing and normalizing the QNMs of micro- and nanoresonators made of highly dispersive materials. We benchmark several methods for three geometries, a two-dimensional plasmonic crystal, a two-dimensional metal grating, and a three-dimensional nanopatch antenna on a metal substrate, with the perspective to elaborate standards for the computation of resonance modes.

Efficient unidirectional and broadband vertical-emitting optical coupler assisted by aperture-coupled nanopatch antenna array.

Vertical-emitting optical couplers that convert in-plane guided light to out-of-plane emission are crucial elements for future photonic integrated circuits. However, traditional vertical-coupling elements, such as grating couplers, by default radiate light in both upward and downward directions, leading to a significant reduction of device efficiency. In this paper, we propose to solve this problem using a novel nanopatch antenna array, inspired by patch antenna theories commonly deployed in microwave circuits. The proposed nanopatch array features an up-to-down emission directionality up to 12.91 dBc and a wide operating bandwidth of over 400 nm simultaneously. Compared with a typical waveguide grating antenna, our design shows a significantly higher free-space gain of 24.27 dBi. The unidirectional, efficient, and broadband antenna arrays presented here are promising for a range of integrated photonics applications, including inter-chip photonic interconnects, light ranging and detection, optical communications, and biological imaging.