Improvement of THz coupling using a tapered parallel-plate waveguide

Abstract

This paper reports an experimental and simulation study of a tapered parallel-plate waveguide (TPPWG) to improve THz coupling to the plate separation gap. The flat- and round-type TPPWG without any silicon lens is compared to the parallel-plate waveguide (PPWG) with a plano-cylindrical silicon lens. The spectrum amplitudes of the input-side TPPWG and the input- and output-side TPPWG both having a 3 degrees slop angle increased about 56% and 103% at 1 THz when compared to that of the PPWG. Since the input- and output-side TPPWG had almost no impedance mismatch to the propagating THz wave, coupling to the waveguide could be improved twice compared with the PPWG.

Adiabatic compression of terahertz waves using metal flares

“…Compared to the results of Kim et al 8 obtained with bulk milled flares ͑coupling ratio of 56% at 1 THz and dropping with higher frequencies͒ our results show a reasonable performance. We believe that our approach, relying only on naturally curved surfaces is advantageous because it is much easier to apply, does not need high precision milling and guarantees a steady smooth surface quality.…”

“…Previous results have shown that the adiabatic compression of the TEM mode within a waveguide is highly efficient, by reducing the input plate separation b from 100 m at the entrance face to 10 m at midwaveguide, and then increasing to 100 m at the output face. 7 As recently shown by Kim et al 8 high precision milled flares can be used to couple and guide free-space THz radiation through a parallel-plate waveguide, thereby eliminating the coupling lenses. Our conceptually similar approach in this paper is based on using standard 100 m thick copper shim ͑cut from a commercial 9 cm diameter shim stock roll using a paper cutter͒ to make the coupling flares.…”

Highly sensitive terahertz measurement of layer thickness using a two-cylinder waveguide sensor

“…Waveguide geometries based on slowly varying metal surfaces have recently attracted interest in the THz range. [8][9][10][11][12][13] Using these results, we propose and demonstrate improved thin film sensing of plastic coatings.…”

Terahertz field enhancement to the MV/cm regime in a tapered parallel plate waveguide

“…It has been recently shown that this limitation can be overcome by use of plasmonic structures and metamaterials [3][4][5][6][7][8]. A significant effort in achieving deep subwavelength confinement has been focused on the use of tapered waveguides [9][10][11][12][13][14][15]. Zhan et al [13] demonstrated that a tapered parallel plate waveguide (TPPWG) supports superfocusing of THz waves below λ /250.…”