Plasmonic Bowtie Antenna Research Articles

Terahertz Uygulamaları için Grafen Malzemesine Dayalı Mikroşerit Bowtie Anten Tasarımı ve Optimizasyonu

The developments of the wireless communications technology, the Terahertz (THz) frequency band of the electromagnetic spectrum becomes promising and recently has the researchers’ attention to be utilized in several applications such as medical, indoor communications for personal networks, and the military applications. The main issues in this frequency band are the construction of a compact, high-performance antenna design; as in this frequency band, the material properties for conduction decrease as the frequency increases, and therefore the performance of the antenna diminishes. In this paper, we propose a graphene-based bowtie microstrip antenna, the performance of the graphene material in the THz frequency band is analysed based on the finite integration of the Computer Simulation Technology (CST) software. The graphene-based bowtie patch printed on a silicon dioxide substrate with a fully copper ground plane printed on its bottom. The proposed graphene plasmonic bowtie antenna covers a range of 0.1-10 THz band frequency with good gain in the range of 2-19 dBi in the mentioned band.

Efficient single-photon emission from a nanowire quantum dot coupled to a plasmonic nanoantenna

Integration of a single III-V quantum dot with a plasmonic nanoantenna is still underexplored as a means towards efficient single-photon sources. Here, we propose two new concepts based on a nanowire quantum dot (NWQD) emitter coupled with a plasmonic bowtie antenna and an NWQD-plasmonic metal hybrid structure. Based on finite element method modeling, we show how these devices can achieve an enhancement in single-photon emission rate and directional radiation. The plasmonic bowtie can increase the spontaneous emission of NWQD with a small diameter, overcoming their otherwise dominating intrinsic spontaneous emission suppression. Further, the NWQD-plasmonic hybrid structure can act as a single-mode waveguide. These features would facilitate nano-photonic device integration as desired for applications of bright single-photon sources, plasmonic lasers, and on-chip opto-electronic nanodevices.

Sub-femtosecond electron transport in a nanoscale gap

The strong fields associated with few-cycle pulses can drive highly nonlinear phenomena, allowing the direct control of electrons in condensed matter systems. In this context, by employing near-infrared single-cycle pulse pairs, we measure interferometric autocorrelations of the ultrafast currents induced by optical field emission at the nanogap of a single plasmonic nanocircuit. The dynamics of this ultrafast electron nanotransport depends on the precise temporal field profile of the optical driving pulse. Current autocorrelations are acquired with sub-femtosecond temporal resolution as a function of both pulse delay and absolute carrier-envelope phase. Quantitative modelling of the experiments enables us to monitor the spatiotemporal evolution of the electron density and currents induced in the system and to elucidate the physics underlying the electron transfer driven by strong optical fields in plasmonic gaps. Specifically, we clarify the interplay between the carrier-envelope phase of the driving pulse, plasmonic resonance and quiver motion. Single-cycle interferometric autocorrelation measurements of electrons tunnelling across the gap of a plasmonic bowtie antenna and quantitative models provide insight into the physical interactions that drive the electron transfer.

Tailored Emission Properties of ZnTe/ZnTe:O/ZnO Core–Shell Nanowires Coupled with an Al Plasmonic Bowtie Antenna Array

The ability to manipulate light-matter interaction in semiconducting nanostructures is fascinating for implementing functionalities in advanced optoelectronic devices. Here, we report the tailoring of radiative emissions in a ZnTe/ZnTe:O/ZnO core-shell single nanowire coupled with a one-dimensional aluminum bowtie antenna array. The plasmonic antenna enables changes in the excitation and emission processes, leading to an obvious enhancement of near band edge emission (2.2 eV) and subgap excitonic emission (1.7 eV) bound to intermediate band states in a ZnTe/ZnTe:O/ZnO core-shell nanowire as well as surface-enhanced Raman scattering at room temperature. The increase of emission decay rate in the nanowire/antenna system, probed by time-resolved photoluminescence spectroscopy, yields an observable enhancement of quantum efficiency induced by local surface plasmon resonance. Electromagnetic simulations agree well with the experimental observations, revealing a combined effect of enhanced electric near-field intensity and the improvement of quantum efficiency in the ZnTe/ZnTe:O/ZnO nanowire/antenna system. The capability of tailoring light-matter interaction in low-efficient emitters may provide an alternative platform for designing advanced optoelectronic and sensing devices with precisely controlled response.

Ultra-high Q/V hybrid cavity for strong light-matter interaction

The ability to confine light at the nanoscale continues to excite the research community, with the ratio between quality factor Q and volume V, i.e., the Q/V ratio, being the key figure of merit. In order to achieve strong light-matter interaction, however, it is important to confine a lot of energy in the resonant cavity mode. Here, we demonstrate a novel cavity design that combines a photonic crystal nanobeam cavity with a plasmonic bowtie antenna. The nanobeam cavity is optimised for a good match with the antenna and provides a Q of 1700 and a transmission of 90%. Combined with the bowtie, the hybrid photonic-plasmonic cavity achieves a Q of 800 and a transmission of 20%, both of which remarkable achievements for a hybrid cavity. The ultra-high Q/V of the hybrid cavity is of order of 106 (λ/n)−3, which is comparable to the state-of-the-art of photonic resonant cavities. Based on the high Q/V and the high transmission, we demonstrate the strong efficiency of the hybrid cavity as a nanotweezer for optical trapping. We show that a stable trapping condition can be achieved for a single 200 nm Au bead for a duration of several minutes (ttrap > 5 min) and with very low optical power (Pin = 190 μW).

Ultra-Broadband Excitations of Plasmonic Waveguides by Bowtie Apertures

The plasmonic bowtie antenna constantly attracts researchers’ interests recently. In this paper, we design and demonstrate polarization sensitive and ultra-broadband excitations of plasmonic waveguides. The structure is composed of a bowtie aperture aligned near a stripe waveguide, which is fabricated on a single silver layer on top of a silica substrate. The dependence of resonance spectra on the arm length of the bowtie aperture is simulated. Only when the incident polarization is parallel to the waveguide direction, the plasmonic bound modes can be correctly excited. Importantly, an extremely wide spectrum bandwidth of 610 nm which covers most of the visible region from 500 nm till the near infrared light of 1 μm is achieved. Our investigations will have intensive applications in next-generation plasmonic integrated chips and functional devices.

Graphene based plasmonic terahertz amplitude modulator operating above 100 MHz

The terahertz (THz) region of the electromagnetic spectrum holds great potential in many fields of study, from spectroscopy to biomedical imaging, remote gas sensing, and high speed communication. To fully exploit this potential, fast optoelectronic devices such as amplitude and phase modulators must be developed. In this work, we present a room temperature external THz amplitude modulator based on plasmonic bow-tie antenna arrays with graphene. By applying a modulating bias to a back gate electrode, the conductivity of graphene is changed, which modifies the reflection characteristics of the incoming THz radiation. The broadband response of the device was characterized by using THz time-domain spectroscopy, and the modulation characteristics such as the modulation depth and cut-off frequency were investigated with a 2.0 THz single frequency emission quantum cascade laser. An optical modulation cut-off frequency of 105 ± 15 MHz is reported. The results agree well with a lumped element circuit model developed to describe the device.

Offset semi-parabolic nanoantenna made of a photonic crystal parabolic mirror and a plasmonic bow-tie antenna.

In a parabolic mirror, light coming parallel to the antenna passes through its focal point. In this work, a waveguide feeds a semi-parabolic photonic crystal mirror and the emerging beam feeds a bow-tie antenna placed at the mirror's focal point-it is shown that the antenna system can not only feed a bow-tie antenna (producing a localized moderately high electric field) but also produces a directional radiation beam. The semi-parabolic mirror is also modified to reduce reflection back to the feeding waveguide.

ANALYSIS OF A WIDE SPECTRAL RANGE PLASMONIC OUTLINE BOWTIE ANTENNA RANGING IN 0.3-5.0 μm

We numerically analyze a broadband plasmonic outline bowtie antenna over a large parameter space by means of finite element method with three-dimensional calculation. The antenna is composed of a pair of triangular gold with outline shape placed in close proximity to each another. We show how the structural parameters affect the antenna resonance conditions, such as peak resonances wavelengths, electric field intensities, propagation properties, component field and total field distributions, charge densities and electrical filed stream lines at spectral points of interest. In addition, the characteristics of transmittance spectral of a periodic antenna array corresponding to the bonding mode and anti-bonding mode are investigated as well. Simulation results show that it is possible to tune an antenna with a constant length over a wide spectral range (ranging in 0.3–5.0μm or more range) while maintaining a constant antenna dimension, reduce the antenna footprint by a factor of 4.98, and increase the gap enhancement by 23%. This article has been removed from the website on January 3, 2013, because it has been found to violate plagiarism rule of our journal. Received 18 October 2012, Accepted 16 November 2012, Scheduled 7 December 2012 * Corresponding author: Yuan-Fong Chau (yfc01@uch.edu.tw).

Enhanced terahertz extinction of single plasmonic antennas with conically tapered waveguides

We demonstrate experimentally the resonant extinction of terahertz (THz) radiation by a single plasmonic bowtie antenna, formed by two n-doped Si monomers with a triangular shape and facing apexes. This demonstration is achieved by placing the antenna at the output aperture of a conically tapered waveguide, which enhances the intensity of the incident THz field at the antenna position by a factor of 10. The waveguide also suppresses the background radiation that is otherwise transmitted without being scattered by the antenna. Bowtie antennas, supporting localized surface plasmons, are relevant due to their ability to resonantly enhance the field intensity at the gap separating the two triangular elements. This gap has subwavelength dimensions, which allows the concentration of THz radiation beyond the diffraction limit. The combination of a bowtie plasmonic antenna and a conical waveguide may serve as a platform for far-field THz time-domain spectroscopy of single nanostructures placed in the gap.

Nanoscale plasmonic contour bowtie antenna operating in the mid-infrared

A plasmonic antenna design is proposed and investigated numerically over a large parameter space. By considering the contour of a bowtie antenna and introducing an additional design parameter, the contour thickness, it is demonstrated that the resonant wavelength of the antenna may be tuned over a broad spectral range while maintaining a constant antenna footprint. These new antennas allow for a factor of 3.6 reduction in the antenna footprint and an increase in the gap enhancement by 28%.

Single defect centers in diamond nanocrystals as quantum probes for plasmonic nanostructures

We present two applications of a single nitrogen vacancy center in a nanodiamond as quantum probe for plasmonic nanostructures. Coupling to the nanostructures is achieved in a highly controlled manner by picking up a pre-characterized nanocrystal with an atomic force microscope and placing it at the desired position. Local launching of single excitations into a nanowire with a spatial control of few nanometers is demonstrated. Further, a two dimensional map of the electromagnetic environment of a plasmonic bowtie antenna was derived, resembling an ultimate limit of fluorescence lifetime nanoscopy.

A New Type of Optical Antenna: Plasmonics Nanoshell Bowtie Antenna with Dielectric Hole

We first investigate plasmonic nanoshell bowtie nanoantenna with dielectric hole that interact with incident plane wave of transverse-magnetic polarization by use of the finite element method. The influence of the dielectric hole in nanoshell on the antenna field enhancement and spectral response is discussed. Results show that the proposed plasmonic nanoshell bowtie antenna can confine the field in a volume well below the diffraction limit and exhibit tunable surface plasmon resonances in a wider range of wavelength that are not observed for the conventional solid-gold case with the same volume. This offers a new possibility to further optimize the performance of optical nanoantenna.