Spoof Surface Plasmon Polaritons Transmission Research Articles

A terahertz metamaterial biosensor based on spoof surface plasmon polaritons transmission line for avian influenza virus detection

A highly sensitive terahertz biosensor based on spoof surface plasmon polaritons for avian influenza virus detection is presented in this paper. The sensor utilizes a grating structure to support spoof plasmon modes with high-quality factors, enabling detection at 1.93 THz with a Q-factor of 690. The slow-wave transmission lines (SWTL) are connected to a metamaterial unit cell to achieve strong field confinement and resonance at terahertz frequencies. Various types of the H1N1, H5N2, and H9N2 are considered as material under test which is placed over the sensor. The main elements for controlling the resonance and increasing the Q-factor are the width of the gap and the unit-cell and the parametric studies show that the selected dimensions are optimum for this sensor. The high sensitivity is attributed to the excitation of spoof plasmons that concentrate the terahertz field within micro-scale regions, interacting with minute amounts of analyte. The full-wave method of the finite integrated technique (FIT) as a high-accuracy time domain method is used for the simulation of the proposed structure and it is compared with the finite element method (FEM) for confirming the results. Moreover, the transmission line model (TL) and circuit model (results) are extracted which prove the truth of the full-wave results. The average sensitivity (Savg) of this sensor for material in the range of 1.1 to 1.5 is obtained up to 8 %. This work demonstrates the application of plasmonic metamaterials to terahertz biosensing for virus detection with high sensitivity.

Wearable Full-Textile Spoof Surface Plasmon Polariton Transmission Line for Secured Communication in Wireless Body Area Network

Wearable Full-Textile Spoof Surface Plasmon Polariton Transmission Line for Secured Communication in Wireless Body Area Network

Single-Conductor Spoof Surface Plasmon Polaritons Transmission Line With Bandpass Feature Based on Embedded Cross-Shaped Resonators

In this brief, cross-shaped resonators (CSRs) are integrated in spoof surface plasmon polaritons (SSPPs) unit, and a novel compact single-conductor SSPPs transmission line (TL) with bandpass feature is proposed. In this design, a unit structure based on classical SSPPs structure embedded with a CSR is proposed. To analyze the proposed unit structure, scattering parameters and ABCD-matrix theories are used. After the theoretical analysis, a SSPPs TL with bandpass filtering property is designed. The simulated passband is from 7.9 to 12.2 GHz with a relative bandwidth of 42%. A prototype is fabricated and measured. The measured results are in agreement well with the simulated ones. This proposed structure is attractive and useful for the design of high integrated SSPPs circuits.

Measurement Method for the Dispersion Curves of a Spoof SPP Transmission Line Using a Single Sample

Research works on spoof surface plasmon polariton (SPP) transmission lines (TLs) have been carried out toward the goal of achieving flexible control of dispersion. The existing measurement methods for the dispersion of the spoof SPPs require two SPP TL samples with different numbers of units and transition structures, which makes the process more difficult and expensive. This work proposes a new approach for measuring the dispersion curve of a spoof SPP TL by using experimental near-field data. A mathematical model is presented to describe the relation between the wavenumber <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> and the near-field data by considering the presence of reflected waves. The high efficiency and accuracy of this method are verified by the good agreement obtained between the measured dispersion curve and the eigenmode simulation result for a typical spoof SPP TL. Hence, the proposed method makes it possible to measure the dispersion curve of a spoof SPP TL based on a single sample, providing significant progress toward decreasing testing error and cost.

Cascaded plasmon-induced transparency in spoof surface plasmon polariton waveguide

Manipulating spoof surface plasmon polaritons (SPPs) effectively has promising applications in developing ultracompact plasmonic circuits. Research on versatile components in planar spoof SPP waveguides has attracted widespread attention over the decades. In particular, cascaded chip-scale devices play an important role in enhancive buffering, highly-sensitive sensing and nonlinear interaction. Herein, we propose a novel strategy to manipulate the switching and slow wave features of spoof SPPs on the basis of plasmon-induced transparency (PIT) spectral responses. A combined module consisting of split square-ring resonators and electric-LC resonators is loaded with a spoof SPP waveguide along the propagating trajectory, where the destructive interference between the two resonators contributes to the PIT behavior and the group delay of the spoof SPPs. A modulation contrast of up to 16.2 dB is achieved for the spoof SPP transmission at the PIT peak frequency. The measurements are consistent with both full-wave simulations and theoretical calculations. Cascaded capabilities performed by installing multiple PIT modules at an interval of an equivalent wavelength are accomplished in the planar spoof SPP waveguide. The proposed strategy opens up fascinating prospects on highly integrated plasmonic circuits and networks.

Spoof surface plasmon polaritons transmission lines with line‐width reduction based on miniature unit structures

Spoof surface plasmon polaritons transmission lines with line‐width reduction based on miniature unit structures

Ultra-compact on-chip spoof surface plasmon polariton transmission lines with enhanced field confinements

On-chip transmission lines (TLs) for spoof surface plasmon polariton (SSPPs) have been proved to suppress on-chip channel crosstalk in terahertz band due to their field confinement property. But the contradiction between strong field confinement and miniaturization limits the application of the on-chip SSPP TLs in millimeter and terahertz bands. Here, an ultra-compact on-chip SSPP TL with strong field confinement is proposed using 0.18 μm CMOS technology. The proposed SSPP TL reduces the cutoff frequency down to 435 GHz in a very limited TL width. Broadband feeding without using gradient transition structures is presented to guarantee the compact size. Compared to microstrip and the typical SSPP TLs, outstanding field confinement of the novel on-chip SSPP TL is demonstrated by the electrical-field- intensity distributions. Measured result matches to simulated one well. It is shown that the proposed on-chip SSPP TL possesses the lowest cutoff frequency and the smallest width relative to the cutoff wavelength, compared to the microstrip and the typical SSPP TLs. Thus the ultra-compact on-chip SSPP TL with strong field confinement may be widely used in the future miniaturized monolithic microwave integrated circuits.

An Ultra‐Compact Spoof Surface Plasmon Polariton Transmission Line and Its Signal Integrity Analysis

An ultra‐compact spoof surface plasmon polariton (UCSSPP) transmission line (TL) based on a meander line is proposed, which can achieve almost the same transmission performance as the conventional rectangular‐groove SSPP TL, but the linewidth is greatly reduced by more than 40%. The coupling effect between two UCSSPP TLs in different line arrangements has been well studied, revealing that excellent crosstalk suppression can be achieved when two TLs are arranged back‐to‐back, while strong coupling occurs when they are arranged face‐to‐back or face‐to‐face. The signal integrity of back‐to‐back UCSSPP TLs is analyzed and demonstrated, which shows that the signal integrity can be greatly improved compared with microstrip (MS) TLs. In addition, based on the principle of mode mismatch, MS and UCSSPP TLs are arranged alternately to solve the mutual coupling problem in multi‐line systems. In contrast, benefiting from the strong coupling of face‐to‐face UCSSPP TLs, an ultra‐miniaturized SSPP coupler working at 9 GHz is designed, whose size can be reduced by over 75% compared with conventional MS coupler. The measurement results show good agreement with full‐wave simulations, indicating that the proposed UCSSPP TL has significant advantages in signal integrity and device miniaturization over previously reported SSPP TLs.

T-shaped double-strip spoof surface plasmon polariton transmission lines and application to microwave resonators

A microwave double-strip spoof surface plasmon polariton (DS SSPP) is proposed for high-speed interconnects and high-performance microwave circuits. Based on the dispersion analysis, a T-shaped double-strip structure is designed to provide strong surface- and slow-wave properties from very low to very high frequencies (~ 40 GHz). It allows the tight field confinement and greatly reduces the electromagnetic wave leakage. It exhibits broadband performance with reduced ripples in the insertion loss. It also shows more constant group delay and impedance than counterpart single-strip SSPP. The compact coaxial-to-microstrip-to-DS SSPP transition are designed using gradient grooves. The measurement shows that the DS SSPP lines can exhibit the lower coupling and lower insertion loss than the microstrip lines, so that the former is well-suited for the densely packed high-speed interconnects. The designed DS SSPP is utilized for high quality (Q)-factor microwave ring resonator. The measured unloaded Q-factor is 107.9 at the resonant frequency of 8.7 GHz, which is 1.3 times higher than the microstrip ring resonator. It is found to be caused by the reduction of the radiation loss, according to the loss analysis. The size is also reduced due to the short wavelength, occupying 56.8% of that of the microstrip ring resonator. Therefore, the proposed T-shaped DS SSPP can be also applied for high-performance miniaturized microwave circuits.

Embroidered Spoof Surface Plasmon Polariton Transmission Line for Wireless Body Sensor Network

A wearable Spoof Surface Plasmon Polariton Transmission Line (SSPP TL) operating at 2.45 GHz designed for embroidery production and on-body communication is proposed. The SSPP TL supports both even and odd modes launched by near field coupling with a dipole antenna perpendicular and parallel to the TL, respectively. First, the experimental dispersion curves and transmission for the even and odd modes are favourably compared to simulations. Then, experimental transmission for each mode is compared with the Line-Of-Sight (LOS) transmission between two parallel-oriented antennas. At 2.45 GHz, a transmission enhancement of 16 dB is measured for the even mode and it reaches up to 37 dB for the odd mode. A transmission enhancement of 30 dB is also measured at 2.45 GHz between two antennas with orthogonal orientations. Performances of the SSPP TL for Wireless Body Sensor Network are evaluated. Transmission is sustained for the SSPP TL under curvature and right angle bending. Transmission measured when both an arm and a copper plate obstacle between antennas were surrounded by the curved SSPP TL is compared with the obstructed LOS transmission. Measurements show a transmission enhancement up to 22 and 25 dB for the even and odd modes, respectively.

Design of Compact Sub-Terahertz Spoof Surface Plasmon Polariton Transmission Line Based on InP Technology

Design of Compact Sub-Terahertz Spoof Surface Plasmon Polariton Transmission Line Based on InP Technology

Generation of dual-band rejection filtering function in two frequency bands developed by spoof surface plasmon polaritons

In this paper, we propose the generation of dual-band rejection filters based on the interaction between spoof surface plasmon polaritons transmission line and -type resonator cells. By selecting a suitable value of spacing inside them, the -type resonator cells generate excellent dual-band band rejection filter on combining with spoof SPP transmission line in lower frequency band. A simple parametric calculation based on varying the value of spacing inside -type resonator cells, has been performed for the conversion of dual-band band rejection filter from lower frequency band to higher frequency band. Greater value of spacing results in larger LC coupling which deteriorate filtering performance by leaving us with dual-band rejection filtering function in lower frequency band. By choosing smaller value of spacing converts it into dual-band rejection filtering function in upper frequency band because of significant reduction in LC coupling, and hence leading to much improved broadband filtering performance. In short, the formation of dual-band rejection filter in lower frequency band and its conversion into dual-band rejection filter in upper frequency band can be fully controlled by just adjusting the value of vertical width inside -type resonator cells. The simulation results demonstrate the outstanding performance of the proposed filters and can play a crucial role in developing integrated plasmonic circuits at microwave and terahertz frequencies.

Short-circuited stub-loaded spoof surface plasmon polariton transmission lines with flexibly controllable lower out-of-band rejections.

This Letter proposes an approach to develop a spoof surface plasmon polariton (SSPP) transmission line (TL) by loading short-circuited (SC) shunt stubs. Lower out-of-band rejections can be flexibly controlled without affecting the upper cutoff frequency by independently modifying the stubs. Dispersion analysis of the SSPP unit is realized by theoretical calculation and circuit simulation to predict the upper cutoff frequency of the proposed SSPP TL simultaneously. Also, parametric sweeping of the SC shunt stubs is performed based on circuit simulation to investigate their impacts on the lower and upper out-of-band rejections of the proposed SSPP TL. In addition, electric field distributions of different types of TLs are simulated and compared to study the transmission characteristics of the proposed SSPP TL. The lower cutoff frequency can be flexibly tuned in a wide range, from 1.2 to 2.1 GHz, in the simulations. The measured 3-dB fractional bandwidth is about 128.1%, covering a range from 1.19 to 5.43 GHz. The numerical and experimental results are compatible, which verifies the feasibility of the proposed approach. This approach can offer more convenience and flexibility for controlling the rejections of the SSPP by introducing up to four tuning parameters. More importantly, the proposed SSPP TL avoids using the substrate integrated waveguide (SIW) technique, which shows the potential to decrease the transverse width (0.44λg), especially at lower frequencies (e.g., 1.2 GHz), and to reduce the complexity in designing the high-efficiency transition. This work paves the way for the development of novel SSPP-based microwave devices.

Spoof surface plasmon polariton‐based switch using liquid metal

By virtue of good liquidity and high conductivity of the liquid metal, a radio frequency (RF) switch based on the spoof surface plasmon polariton (SPP) transmission line is investigated in this paper. The SPP transmission line with H-shaped unit cells are used here and the signal can be successfully blocked by cutting several unit cells. By introducing a micro-channel containing the liquid metal, the SPP transmission line can be reformed with the liquid metal slug. Different states of the switch can be obtained via moving the liquid metal slug by microfluidic technology. The prototype of the presented switch is fabricated and measured and good agreement between the simulation and measurement can be observed. Low insert loss at ON state and high isolation at OFF state can be obtained over the operation band.

Spoof Surface Plasmon Polariton Filter With Reconfigurable Dual and Non-Linear Notched Characteristics

In this brief, we propose a spoof surface plasmon polariton (SPP) filter with reconfigurable dual and non-linear notched frequencies. The SPP waveguide with asymmetrical geometry leads to asymmetrical field confinement depending on the groove orientation. By loading half-wavelength SPP resonators along the weaker field confinement side of the asymmetrical SPP waveguide, dual notches can be generated in the SPP transmission. Meanwhile, since the dispersion of SPP cell is not linear, the dual notched frequency locations are also non-linearly spaced. Varactor diodes, with voltage controllable capacitance, are incorporated into the SPP resonators to engineer the SPP non-linear dispersion. Thus, the SPP effective wavelength can be altered and the dual-notched frequencies be tuned. Two reconfigurable notched frequencies are achieved at 4.29/5.69, 4.045/5.27 and 3.765/4.85 GHz with 16, 4.5 and 0 V bias, respectively.

Electromagnetic metamaterials&amp;mdash;from effective media to field programmable systems

Electromagnetic metamaterials are periodic or nonperiodic artificial structures comprising basic elements in subwavelength scales. They can be used to control electromagnetic waves by designing the basic elements and their spatial arrangements. Metamaterial has been a research hotspot in physical and information sciences. In this review, I present the history and main progresses achieved in metamaterial studies conducted in the State Key Laboratory of Millimeter Waves at Southeast University, which were performed in three stages. In the first stage, we improved the developments in effective-medium metamaterials. In particular, we proposed a general theory to accurately describe the effective permittivity and permeability of metamaterials. Based on the general theory, we designed and realized a three-dimensional (3D) wideband ground-plane invisibility cloak, free-space electrostatic invisibility cloak, electromagnetic black hole, electromagnetic illusions, and radially anisotropic zero-index metamaterial for omni-directional radiations and nearly perfect power combinations of source arrays. Moreover, we undertook significant efforts in engineering applications of microwave metamaterials, such as broadband and low-loss 3D transformation-optic lens for wide-angle scanning, 3D planar gradient-index lens for high-gain radiations, and random metasurfaces to reduce radar cross sections. In the second stage, we opened up a new direction of plasmonic metamaterials from the viewpoint of microwave transmission lines. We proposed an ultrathin, narrow, and flexible corrugated metallic strip to guide spoof surface plasmon polaritons (SPPs) with small bending and radiation losses, based on which we designed and realized a series of passive SPP devices (such as power divider, coupler, filter, and resonator), active SPP devices (such as amplifier and duplexer) and SPP antennas in the microwave bands. We demonstrated a significant feature of the ultrathin SPP transmission line in overcoming challenges of signal integrity existing in the traditional integrated devices and circuits. We built up a full-SPP wireless communication system with unique properties to remotely transmit two movies in two deep-subwavelength-distance channels exhibiting excellent performance. In the third stage, we established a new area of metamaterial-information metamaterial. We proposed to describe the metamaterial using digital coding from the information science viewpoint, which directly resulted in a new kind of metamaterial-digital coding metamaterial. We theoretically and experimentally illustrated that the digital coding metamaterials comprising digital units can be controlled using different coding sequences to achieve different functions. When the digital state of the coding unit was controlled using a field programmable gate array (FPGA), we realized a field programmable metamaterial that can manipulate electromagnetic waves in real time and generate numerous different functions using a single piece of hardware. The digital coding metamaterial provides a platform to establish a digital space on the physical space and enriches the methodology and theory of metamaterials. We proposed measuring the information capacity of metamaterials using Shannon entropy and presented the convolution and addition theorems on metamaterial platforms, which can be used to simultaneously control the physical properties and digital information. Based on information metamaterials, we established new-architecture microwave imaging systems, wireless communication systems, and other intelligent information systems.

Spoof surface plasmon polariton transmission line with reduced line‐width and enhanced field confinement

This article proposes a compact spoof surface plasmon polaritons (SSPPs) transmission line, by introducing capacitive loading metal strips to manipulate the dispersion characteristics and electromagnetic field confinement. Results validate that, compared with conventional rectangular-grooved SSPP structure, the proposed SSPP transmission line features a line-width reduction up to 53%, and moreover a tighter field confinement, that is, 67% reduction of confinement area. This proposed structure can be further implemented in silicon process with multiple metal layers for on-chip transmission of terahertz signals.

Tri-Band Band-Pass Filter Based on Multi-Mode Spoof Surface Plasmon Polaritons

This paper presents a novel tri-band bandpass filter based on multi-mode spoof surface plasmon polaritons (SSPPs) in microwave frequencies. The combination of multi-mode resonance and cutoff characteristic of SSPPs contributes to a tri-band bandpass response. The proposed SSPPs-based filter consists of two coplanar waveguides, two conversion parts and a SSPPs transmission structure made of five unit-cells. Each unit cell is a multi-mode resonator, which is constructed by a pair of oppositely oriented double-side folded strips, and the ends of folded strips are placed closely to form coupled-stubs. Two distinct passbands divided by a sharp stopband are produced under the cutoff frequency of SSPPs transmission structure. The third passband above the cutoff frequency is introduced by the resonant tunneling effect due to the self-resonant mode of proposed SSPPs unit cell. Dispersion relations, electric field distributions and proposed equivalent transmission line model give a physical insight into the filter operating mechanism. As a demonstration, a prototype of the proposed filter has been fabricated and measured. The measurement results demonstrate that the proposed filter has a tri-band bandpass performance with excellent frequency selectivity, which may be very useful in many applications, such as multi-band wireless systems.

Crosstalk Suppression Based on Mode Mismatch Between Spoof SPP Transmission Line and Microstrip

We propose an efficient method to suppress the crosstalk based on the mode mismatch between spoof surface plasmon polariton (SPP) transmission line (TL) and microstrip. Since microstrip and spoof SPP TL support quasi-transverse electromagnetic (quasi-TEM) wave and transverse magnetic (TM) wave, respectively, the transmitting electromagnetic (EM) energy can hardly be coupled between these two kinds of TLs, which helps to reduce the crosstalk. For the cases of weak and strong coupling, two kinds of structures of spoof SPP TLs are designed. To verify the performance of crosstalk suppression, two samples of the coupled TLs are presented and fabricated. Simulated and experimental results show that the crosstalk of both strong and weak coupling is reduced by approximately 35 and 30 dB, respectively, by introducing the spoof SPP TL into the microstrip pair. Thus, crosstalk in traditional circuits can be alleviated by the mode mismatch between spoof SPP TLs and microstrips, which is significant for high-speed and high-density integrated systems.

Tunable spoof surface plasmon polariton transmission line based on ferroelectric thick film

Spoof surface plasmon polaritons (SSPPs) provide a high field confinement in the sub-wavelength scale and low transmission loss in the propagation, which are widely used in microwave functional devices. In this paper, we first propose a tunable SSPP transmission line (TL) based on ferroelectric thick film. The ferroelectric thick film associated with the SSPP planar waveguide can provide an electrically tunable transmission phase. Two electric-field-coupled inductive–capacitive (ELC) resonators are added in the configuration to inspire the coupling between ELC resonant modes and SSPPs, enabling the tunable TL to work in the frequency-selective transmission passband. It is demonstrated that the SSPP mode can be designed in higher or lower confinement to modulate the electromagnetic field strength inside the ferroelectric thick film. This property promotes a balanced design between low transmission loss and large phase change for tunable TL. As a result, this study provides an alternative route to design tunable SSPP devices based on ferroelectric thick film, which may open up new applications in tunable microwave devices.