Enhancing the Dual-Band Guiding Capabilities of Coaxial Spoof Plasmons via use of Transmission Line Concepts

We derive closed analytical forms for the response of coaxial spoof plasmons, aided by transmission line concepts under the effective complex surface impedance framework. This constitutes a powerful platform to improve as well as to elucidate designs with enhanced performances. In particular, we propose a dual-band spoof plasmon waveguiding geometry with the higher order slow-wave mode operating well below the regime governed by dispersion of periodic guides (Bragg reflections at Brillouin zone boundaries), that is, diffraction. The analysis is supported by eigen mode numerical calculations. As an example in a waveguide device context, we demonstrate the dual-band planar routing ability of elliptical–coaxial cable-based spoof plasmons along a straight chain as well as a Y-splitter.     

Design,Analysis, and Characterization of Designer Surface Plasmon Polariton-Based Dual-Band Antenna

This paper reports development, design, and analysis of designer (or spoof) surface plasmon polariton-based feeding configuration to excite a dual-band antenna. As an example, a planar transverse electric and magnetic horn antenna is designed and fed by the proposed transition structure. Designer surface plasmon polariton modes are supported by a metal surface at microwave frequency when it is corrugated with periodical grooves. An efficient transition for converting quasi-transverse electric and magnetic waves of microstrip line into spoof surface plasmon polariton (SSPP) waves has been designed in microwave frequency range using periodically corrugated metal strip. SSPP wave is confined at the teeth part of the corrugation. Simulated and measured reflection and transmission characteristics are in good agreement. The spoof SPP-fed dual-band antenna is designed, fabricated, and characterized in microwave anechoic chamber and measured results are coincident with simulated results.     

Spoof Localized Surface Plasmons Excited by Plasmonic Waveguide Chip with Corrugated Disk Resonator

We designed and fabricated a millimeter plasmonic chip consisted of coplanar waveguide (CPW) and plasmonic waveguide with one corrugated disk resonator (CDR). The spoof localized surface plasmon (LSP) resonance modes can be excited by the interaction between plasmonic waveguide and CDR. Fundamental and higher order sharp spoof LSP resonances (from dipole to dodecapole) were observed in the transmission coefficient spectrum. The Q-value as high as 268.3 (octupole) was experimentally obtained. Experimental results show good agreement with theoretical and simulated ones. All the results may have potential applications in microchip based sensing and filtering.     

Experimental Demonstration of Spoof Surface Plasmon Based THz Antennas for Huge Electric Field Enhancement

Plasmonics - We experimentally demonstrate the fabrication and optical measurement of a novel terahertz antenna array due to the excitation of spoof surface plasmon modes. With the unit cell...     

Spoof Surface Plasmon Polariton-Based Reconfigurable Band-Pass Filter Using Planar Ring Resonator

Plasmonics - In this paper, we report the design, analysis, and development of spoof surface plasmon polariton (SSPP)-based reconfigurable band-pass filter using a planar ring resonator. A...     

Leaky Wave Antenna Based on Periodically Truncated SSPP Waveguide

Plasmonics - The guided waveguide structures based on surface plasmons can be used to miniaturize microwave devices. By simply introducing a series of periodic truncation slits in the SSPP (spoof...     

Design and Analysis of Ultra-wideband and Miniaturized Bandpass Filter Based on Spoof Surface Plasmon Polaritons

Plasmonics - In this paper, a novel miniaturized and ultra-wideband (UWB) bandpass filter (BPF) based on spoof surface plasmon polariton (SSPP) mode is investigated and experimentally demonstrated....     

Tunable Spoof Surface Plasmons Bulleye Antenna

A tunable spoof surface plasmons antenna using sinusoidally modulated corrugated reactance surface based on a bulleye structure is proposed in this paper. The designed antenna is made of concentric metallic grooves etched on a metal plate, the depth of which is of sinusoidal periodic variation in the radial direction. This makes it possible that highly confined spoof surface plasmons along corrugated surface can be converted to radiation modes. The proposed bulleye antenna can work from 25.8 to 33 GHz and a bandwidth of 7.2 GHz and its main lobe can be directed at 30^∘ from the vertical direction at 30 GHz. This antenna has a maximum gain of 15 dB and its main lobe can scan from 14^∘ to 58^∘ by tuning the frequency from 28 to 32 GHz.

     

Structure Metallic Surface for Terahertz Plasmonics

Plasmonics is the field of study of the interaction between incident light and electrons in metals. It is used widely for developing nanophotonic devices. The structured metallic surface such as metamaterials can be used to produce spoof surface plasmons at any frequencies with the dimensions of unit cell less than the incident wavelength. Terahertz plasmonics is attracted to the field of research since it is used for sensing biological components even in a weak environment. The issue with planar metamaterials is a lower quality factor value. Several methods have been adopted for obtaining high Q-value in metamaterials. Among them, Fano- and Toroidal-based metamaterials offer high Q-factor and string localized field enhancement. This article discusses the importance and developments in the field of high-Q terahertz metamaterial for plasmonics applications. The nonlinear responses of terahertz metamaterial under high-intense THz pulses are also discussed.

     

Deep-subwavelength Guiding and Superfocusing of Spoof Surface Plasmon Polaritons on Helically Grooved Metal Wire

Deep-subwavelength guiding and superfocusing of spoof surface plasmon polaritons (SSPPs) realized on a helically grooved metal wire at microwave frequencies are presented in this paper. Two smooth bridges with gradient helical grooves decorated on the cylindrical and conical metal wire are proposed and designed, respectively. High-efficiency and broadband mode conversion from the traditional guided waves to the SSPPs and superfocusing of SSPPs are reported. Numerical simulations quantitatively show that the amplitudes of electric field at the tip of the conical wire with gradient helical grooves can be magnified 50 times more than that of the input signal in broadband. Moreover, the second transition structure ensures that the depth of helical groove can be tuned flexibly and arbitrarily, making it compatible with all kinds of N-type coaxial connectors. Strong field concentration and superfocusing of these two structures can be easily extended to terahertz (THz) frequencies by tuning the geometrical parameters and can find important applications in sensing, spectroscopy and near-field imaging in the microwave and THz frequencies.     

Low-Frequency Surface Plasmon Polaritons Guided on a Corrugated Metal Striplines with Subwavelength Periodical Inward Slits

A new type of stripline-based microwave transmission, which has relatively lower crosstalk compared with the conventional striplines, is proposed. The structure is formed by corrugated inward slit that is subwavelength scale on the edge of the stripline via the photolithography techniques. Numerical simulation is used to analyze the transmission and dispersion properties of this new stripline structure, and the results are experimentally verified in the frequency range from 200 MHz to 8 GHz. We found that spoof surface plasmon polaritons are supported on the new stripline structure whose electromagnetic fields are highly localized near the stripline, and hence the coupling is suppressed between the present type of stripline and the conventional stripline. For a structured stripline and a conventional stripline which are parallelly placed and separated by a distance of the stripline width, the crosstalk between them ranges from −17.13 to −64.89 dB, which is much lower than the crosstalk between two coupled conventional striplines. As this new type of stripline has such an important advantage, it would be applicable to high-density microwave circuits or high-speed circuits.     

Optical Bifacial Transmission by Asymmetric Charge-Oscillation-Induced Light Transmission Through a Plasmonic Structure

From first-principles computation, we reveal that optical bifacial transmission can be induced within an asymmetric metallic subwavelength structure. This phenomenon can be explained by a concrete picture in which the intensity of the driving forces for surface plasmon or charge wave is asymmetric for the two incident directions. Two distinguished different numerical methods, finite difference time domain (FDTD), and rigorous coupled wave analysis (RCWA) are utilized to verify that optical bifacial transmission can exist for linear plasmonic metamaterial. Previous results are also reviewed to confirm the physical meaning of optical bifacial transmission for a planar linear metamaterial. The incident light can provide direct driving forces for surface plasmon in one direction. While in the opposite direction, forces provided by the light diffraction are quite feeble. With the asymmetric driving forces, the excitation, propagation, and light-charge conversion of surface plasmon give the rise of bifacial charge-oscillation-induced transmission. In periodic a structure, the excitation of surface plasmon polariton can lead to the spoof vanish of such phenomenon. The transmissions for two incident directions get the same in macroscopic while the bifacial still exists in microscale.