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.

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Conformal surface plasmons propagating on ultrathin and flexible films

The conversion from spatial propagating waves to surface plasmon polaritons (SPPs) has been well studied, and shown to be very efficient by using gradient-index metasurfaces. However, feeding energies into and extracting signals from functional plasmonic devices or circuits through transmission lines require the efficient conversion between SPPs and guided waves, which has not been reported, to the best of our knowledge. In this paper, a smooth bridge between the conventional coplanar waveguide (CPW) with 50 Ω impedance and plasmonic waveguide (e.g., an ultrathin corrugated metallic strip) has been proposed in the microwave frequency, which converts the guided waves to spoof SPPs with high efficiency in broadband. A matching transition has been proposed and designed, which is constructed by gradient corrugations and flaring ground, to match both the momentum and impedance of CPW and the plasmonic waveguide. Simulated and measured results on the transmission coefficients and near-filed distributions show excellent transmission efficiency from CPW to a plasmonic waveguide to CPW in a wide frequency band. The high-efficiency and broadband conversion between SPPs and guided waves opens up a new avenue for advanced conventional plasmonic integrated functional devices and circuits.

Broadband and high-efficiency conversion from guided waves to spoof surface plasmon polaritons

Thermal physics: Second edition by C. B. P. Finn, Chapman and Hall, London-Glasgow-New York-Tokyo-Melbourne-Madras, 1993 physics and its applications series, volume 5, 256 pages price: ß13.95

In this paper, we report results on an original way to excite surface waves on a single-wire transmission line. Although these waves were proposed many decades ago by Goubau, the novelty of our structures is to achieve a broadband planar excitement. This configuration is very well suited for the terahertz frequency range and allows the investigation of biological entities with high spatial resolution with the use of novel biomicroelectromechanical systems, which include microfluidic functions. From experimental results, we compare different types of transitions from coplanar waveguides, and different substrates are also used. We show that the excitation is highly efficient and broadband for structures on a quartz substrate

Single-wire transmission lines at terahertz frequencies

Aspects of the subject disclosure may include, for example, receiving, by a feed point of a dielectric antenna, electromagnetic waves from a dielectric core coupled to the feed point without an electrical return path, where at least a portion of the dielectric antenna comprises a conductive surface, directing, by the feed point, the electromagnetic waves to a proximal portion of the dielectric antenna, and radiating, via an aperture of the dielectric antenna, a wireless signal responsive to the electromagnetic waves being received at the aperture. Other embodiments are disclosed.

Method and apparatus for coupling an antenna to a device

We propose and demonstrate an original planar excitation of a single wire transmission line also known as Goubau-Line (G-Line). The excitation is based on an electromagnetic transition between a coplanar waveguide and the desired G-line in a planar configuration. We present some characteristics for this line such as its electromagnetic spatial distribution, its velocity, and results in the frequency domain analysis for the transitions. We will also show some results concerning the shape of the G-line and its influence on the transmission level. From these results, we show that there is a great interest for these structures in the field of biological characterization.

Planar excitation of Goubau Transmission Lines for THz BioMEMS

Quite recently, it has been found that conducting wires lying on a flat dielectric substrate can propagate Terahertz (THz) waves in the same way as conducting wires entirely coated with a dielectric (Goubau line). This phenomenon is interesting because it is a basic requirement to fabricate integrated circuits at THz frequencies. The excitation of planar Goubau line (PGL) waves was found to have a very strong Goubau mode on conducting wire. The excitation was made with a coplanar waveguide transition fed with a THz signal obtained from a vector network analyzer. The Goubau mode on PGL was excited with high efficiency (up to 75%.). This is a first step in the design of THz BioMEMS dedicated to living cell investigations. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2998–3001, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23850

New THZ excitation of planar Goubau line

Cold plasma functionalized TeraHertz BioMEMS for enzyme reaction analysis.

Corrugations on planar Goubau lines are presented in order to slow down and focus electromagnetic waves. A propagation effective index shift is observed between corrugated and non-corrugated planar Goubau lines. Influence of the corrugation geometrical parameters is studied. Two original methods based on Bianco-Parodi differential measurements or on THz interferometer structure are validated. Finally, the effect of corrugating lines on unwanted substrate modes reject is discussed with experimental and parametric simulation studies. The wave stronger “attachment” in corrugated configurations is demonstrated.

A. Treizebre

Papers

Single-wire transmission lines at terahertz frequencies

Planar excitation of Goubau Transmission Lines for THz BioMEMS

New THZ excitation of planar Goubau line

Cold plasma functionalized TeraHertz BioMEMS for enzyme reaction analysis.

Corrugated Goubau Lines to Slow Down and Confine THz Waves