Experimental Verification of Low-Loss TM Modes in Dielectric-Lined Waveguide

Abstract

Experimental measurements have been carried out to verify the recent theoretical prediction that, in dielectric‐lined circular waveguide, modes other than those of the TEon family can exhibit a loss characteristic which decreases with increasing frequency. The TM11 waveguide was launched in 51‐mm diameter circular waveguide lined with a 200‐micron layer of polyethylene, and its loss characteristics were measured. Losses of 23 dB/km at 80 GHz and 3.5 dB/km at 110 GHz were measured, thus confirming the decreasing loss with increasing frequency trend predicted by theory.

Modes in silver-iodide-lined hollow metallic waveguides mapped by terahertz near-field time-domain microscopy

“…The visible delay in the dielectric-lined waveguide compared to the metal-only waveguide reflects slightly different group velocities for the dominant modes in the two waveguides. In accordance with the theory of dielectric-lined or corrugated waveguides [2][3][4]8,[15][16][17][18], the coating, even as thin as in our case, slows down the mode propagation. This is evident by comparing the 2D color plots of Figs.…”

“…Experimental and theoretical development in this area started in the millimeter-wave regime [2][3][4]. In light of the high losses suffered by the TE 10 of the traditional rectangular waveguides and the transverse electromagnetic mode of coaxial waveguides, microwave engineers shifted their interest to cylindrical waveguides and their TE 0n modes (where n is an integer and denotes radial variation) because of their low attenuation at high frequencies [5].…”

“…In light of the high losses suffered by the TE 10 of the traditional rectangular waveguides and the transverse electromagnetic mode of coaxial waveguides, microwave engineers shifted their interest to cylindrical waveguides and their TE 0n modes (where n is an integer and denotes radial variation) because of their low attenuation at high frequencies [5]. However, the TE 01 mode is degenerate with the highly lossy TM 11 mode, and researchers then examined strategies to break this degeneracy by, for instance, corrugations [6,7] or dielectric coatings [2][3][4]8,9]. Corrugations and dielectric inclusions were also designed to transform the TE 11 eigenmode of the cylindrical waveguide to the optical-fiber-like hybrid HE 11 mode.…”

“…Corrugated waveguides have been the mainstream in high-energy science where strong interaction with an axial electron flux is pursued [12,13] and an active line in antenna research [6,14]. Dielectric-lined cylindrical waveguides were meanwhile developed for communication systems [2][3][4]; however, they were abandoned later in favor of optical fibers. These waveguides were recuperated subsequently for high-power delivery as well as for surgical applications with midinfrared lasers [15,16].…”

Silver-Coated Teflon Tubes for Waveguiding at 1–2 THz

“…By introducing a dielectric coating on the inner metallic walls of an oversized waveguide (as a rule of thumb,~λ 0 /4 thick), the waveguide dominant mode becomes the linearly polarized hybrid HE 11 mode [1][2][3][4][5][11][12][13][14][15][16]. This HE 11 mode is advantageous because it suffers low losses and it couples efficiently to freespace linearly polarized Gaussian beams [11,17].…”