Terahertz transmission lines based on surface waves in plasmonic waveguides

Abstract

Effect of a dielectric coating on terahertz surface plasmon polaritons on metal wires Appl. Phys. Lett. This paper studies the guided-wave transmission of terahertz electromagnetic waves along the surface waveguides and parallel-plate waveguides ͑PPWGs͒. Field analysis is presented to show that low-loss and quasi-TEM propagation is only possible when the waveguides are operating in their plasmonic modes. It is shown that the observed low-loss and quasi-TEM propagation of terahertz waves in the PPWGs is due to resonant coupling of surface plasmons between the two plates. Transmission line models based on the peculiar characteristics of the surface waves associated with the plasmonic modes of the guides are developed and the distinctions with the conventional transmission line theory are highlighted.

Rigorous analysis of the parallel plate waveguide: From the transverse electromagnetic mode to the surface plasmon polariton

“…The analysis of the ideal parallel plate waveguide (with perfect conductor) is carried out in several references [e.g., Pozar , 1997]. More elaborate studies are presented by Mahmoud [1991] and Tayyar et al [2008] who analyze a parallel plate waveguide with different arbitrary surface impedance boundary conditions, or by Ghamsari and Majedi [2008] who use a nonideal metallic conductor. Staffaroni et al [2011] propose an equivalent circuit of a parallel plate waveguide working at optical frequencies.…”

The transition from a TEM-like mode to a plasmonic mode in parallel-plate waveguides

“…Thus, the field amplitude is nearly constant along a line from one plate to the other, and the mode is similar to the conventional uniform TEM mode. 1,22 However, when b is comparable to or larger than ␦, then the mode begins to more closely resemble two-independent surface waves, one on each metal surface, analogous to the hybrid mode described by Barlow. [9][10][11] For finite-width PPWGs, this field distribution also shows strong enhancements at the edges due to the excitation of edge modes.…”

“…We can develop a simple theoretical model to compute this transition frequency and compare to our experimental results. We use the analytical expressions for the TMpolarized waves between two metal plates of infinite width, 22 and model the metal using Drude theory. 23 From these expressions, we can numerically compute the value of the electric field E͑y͒, along the y axis ͑perpendicular to the plate surfaces͒.…”

Broadband Terahertz Source Based on Photomixing in Laser-Assisted Field Emission with Clusters of Carbon Nanotubes

“…This method shows promise for coupling energy from the common junction because it would be possible to obtain an impedance of 50 Ω for TEM mode propagation at THz frequencies with a cut-off frequency of zero Hz (Ghamsari et al, 2008). As was already noted in section 6.2, the common junction of the CNT could be attached to one plate of this transmission line with the other plate grounded.…”

“…A much lower impedance is requried in order to provide greater output power. One possibility is the parallel-plate plasmonic transmission line which can provide an impedance of 50 Ω for TEM mode propagation at THz frequencies with a cut-off frequency of zero Hz (Ghamsari et al, 2008). The common junction of the CNT could be attached to one plate of this transmission line with the other plate grounded.…”