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Surface plasmon polaritons (SPPs) are localized surface electromagnetic waves that propagate along the interface between a metal and a dielectric. Owing to their inherent subwavelength confinement, SPPs have a strong potential to become building blocks of a type of photonic circuitry built up on 2D metal surfaces; however, SPPs are difficult to control on curved surfaces conformably and flexibly to produce advanced functional devices. Here we propose the concept of conformal surface plasmons (CSPs), surface plasmon waves that can propagate on ultrathin and flexible films to long distances in a wide broadband range from microwave to mid-infrared frequencies. We present the experimental realization of these CSPs in the microwave regime on paper-like dielectric films with a thickness 600-fold smaller than the operating wavelength. The flexible paper-like films can be bent, folded, and even twisted to mold the flow of CSPs. [ABSTRACT FROM AUTHOR]

Novel and compact triple-mode resonators have been investigated and designed using split-ring resonator (SRR) to obtain three controllable resonant frequencies. An even/odd-mode method is proposed. The current distributions are computed by commercial software. Several triple-mode resonators are designed and fabricated. Both simulation and measurement results are presented to show the good performance of the resonators, which have excellent agreements. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2918–2922, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22955 [ABSTRACT FROM AUTHOR]

Open cavities are investigated using properly designed right-handed (RH) and left-handed (LH) transmission-line media (TLM), with detailed formulations to design TLM. We demonstrate large fields and high energies are concentrated at the center because of the resonance, which is a strong localization of electromagnetic waves and energies. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1662–1665, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21689 [ABSTRACT FROM AUTHOR]

We propose a broadband slow-wave system based on metallic graded grating structures of subwavelength thickness. A metal wire is used to excite the slow waves propagating along the gratings. The analysis and full-wave simulations show that the electromagnetic waves could be stopped at designed positions under different frequencies. Experiments are conducted in the microwave frequencies to verify the proposed system. The measured results show very good agreements to the full-wave simulations. We have further modeled a broadband slow-wave system of subwavelength thickness in the terahertz (THz) frequencies to demonstrate its validity. [ABSTRACT FROM AUTHOR]

The wave dispersion characteristics for loop array-based metamaterials were analyzed, based on the general transmission line model of a one-dimensional host medium interacting with a chain of coupled loops. By relating the wave propagation constant and the effective parameters of the coupled host medium, we showed that an active medium embedded with non-Foster loaded loop array can be designed to exhibit broadband negative material parameters with positive gain. Accounting for all interactions, the stability of the active medium was investigated, further yielding necessary design specifications for the non-Foster loads. Subsequently, an experimental demonstration was provided to verify the theoretical analysis, showing that stable reconfigurable broadband gain metamaterials at microwave frequencies can be obtained with proper negative impedance converter design. [ABSTRACT FROM AUTHOR]

We propose a robust method to design arbitrarily directional cloaks by solving the Laplace’s equation. The method is based on the orthogonality between light rays and eikonal curves. By employing the analogy between light rays and electric force lines, and the equivalence between eikonal curves and isopotential lines, the original problem in the geometrical optics is converted into a boundary value problem in electrostatics. Examples are given and the simulation results validate the design. The method can also be used to design other optical-transformation devices and be extended to solve three-dimensional problems. The medium parameters designed by the method are easily realized using metamaterials or normal materials, and hence, the method can find applications in the optical and microwave engineering. [ABSTRACT FROM AUTHOR]

We propose and experimentally demonstrate a broadband illusion device--"electromagnetic gateway" at microwave frequencies. The device is first realized using crossed split-ring resonator and wire unit cells, which can provide the desirable double-negative parameters through fine geometrical designs. Taking into account the complexities in practical realization, we then simplify the original design by using only half of the unit cells. Both simulation and experimental results verify the good abilities of the simplified gateway device in broadband in microwave frequencies. [ABSTRACT FROM AUTHOR]

We propose dynamic control to excite spoof surface plasmon polaritons (SPPs) in the microwave frequency. Using switchable devices, the excitation of spoof SPPs can be turned on and off depending on the DC voltages applied on the switchable devices. To demonstrate the dynamic mechanism, a switchable spoof SPP waveguide is proposed and fabricated in the microwave frequency. Both simulation and measurement results show good performances of the dynamic control in exciting spoof SPPs. [ABSTRACT FROM AUTHOR]

We propose an ultra-wideband plasmonic waveguide based on designer surface plasmon polaritons (DSPPs) with double gratings. In such plasmonic metamaterials, the DSPP waves in the region of lower frequencies of the dispersion curve can be tightly confined and hence effectively broaden the operating bandwidth. Based on such features, we design and fabricate a high performance DSPP filter, in which a transducer consisting of microstrip, slotline, and gradient corrugations is employed to feed electromagnetic energies into the plasmonic waveguide with high efficiency. The simulated and measured results on reflection and transmission coefficients in the microwave frequency demonstrate the excellent filtering characteristics such as low loss, wide band, and high square ratio. The high performance DSPP waveguide and filter pave a way to develop advanced plasmonic integrated functional devices and circuits in the microwave and terahertz frequencies. [ABSTRACT FROM AUTHOR]

A band-stop filter based on spoof surface plasmon polaritons for microwave applications is proposed, which can realise high-efficiency band rejections by etching gradient semi-circular grooves on both sides of the middle stripline of coplanar waveguide. The operating bandwidth and frequency of band-stop can be controlled by changing the radii of semi-circular holes and the length of unit cell, respectively. The operating principle of the designed band-stop filter is explained by the dispersion curves and electric field distributions. Parametric studies are also conducted to analyse the effects of key parameters on the performance of the band-stop filter, which is useful for practical designs. A prototype of the band-stop filter is fabricated and measured. The good agreements between the simulated and measured results validate the proposed design, which indicate that the presented band-stop filter can be potentially useful in many microwave applications. [ABSTRACT FROM AUTHOR]

A planar lens made of gradient index metamaterials can transform cylindrical waves to plane waves, and the beam direction of plane waves is controlled by adjusting the refractive-index distributions of the lens. Based on such properties, we present high-performance beam-scanning antennas experimentally using the gradient-index planar lens and horn antenna. The lens is carefully designed with metamaterials to achieve different refractive indices and good matching of impedance. The near-field distributions of antennas are measured using a two-dimensional near-field microwave scanning apparatus, and the radiation patterns are presented to show the high directivity and low sidelobe. [ABSTRACT FROM AUTHOR]