Efficient localization of terahertz waves within a gradient dielectric-filled metallic grating

Abstract

We proposed a gradient dielectric-filled metallic grating to spatially localize wide-band terahertz waves at different locations for different frequencies. The dispersion relations for terahertz waves propagating along gratings with different filling-depths were developed under the first-order approximation based on the spoof surface plasmon theory. The structure can localize terahertz waves at the frequency regime from 0.7 to 1.3 THz, as the filling-depth H gradually increases from 0 to 50 µm. By filling with active media such as nematic liquid crystals, the trapping location can be effectively tuned, providing potential to realize controllable and compact integrated THz devices.

Excitation of Terahertz Spoof Surface Plasmons on a Roofed Metallic Grating by an Electron Beam

“…The metallic grating has the same groove depth of h , groove width of a and period of d , respectively, as shown in the inset of Figure 1 . A metal plate is introduced to this plasmonic waveguide and the distance of the metal plate from the grating surface is marked by g in the inset of Figure 1 b [ 38 , 39 , 40 , 41 , 42 , 43 , 44 ]. We first consider SSP mode dispersion on the x - z plane, which is assumed to be the transverse magnetic mode (TM) along z and metal is set as the ideal conductor for the study [ 39 ].…”

“…The initial point of the x axis is on the grating surface. The dispersion characteristics of the SSP mode for the open space or roofed metallic grating structure are studied using an effective medium method [ 40 ] or rigorous field expansion method [ 39 , 42 ], as mentioned previously. We here employ a simplified mode matching method to obtain its dispersion property on the metallic grating.…”

“…We here employ a simplified mode matching method to obtain its dispersion property on the metallic grating. For the open space metallic grating or closed metallic grating in Figure 1 , the fields under the metallic surface are the same and can be expressed as homogeneous, based on the fact that the lattice period is usually shorter than the wavelength in the THz band [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]: …”

“…These studies focus mainly on open space metallic grating structures (the inset in Figure 1 a) and the interaction between an electron beam and the SSP mode is also simple. Some recent studies indicate that SSP properties and dispersion diagrams can be largely modified or tuned by introducing a closed metal plate in the vicinity of the metallic grating, namely on the roofed metallic grating (the inset in Figure 1 b) [ 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. Thus, the variation in SSP modes on this kind of roofed metallic grating with different gap sizes should be considered carefully.…”

A semi-analytical method for characterization of fractal spoof surface plasmon polaritons with a transfer matrix and bloch theory

“…Note that other conventional methods, such as mode matching or the modal method, have also often been used in the analysis of conventional structures, such as periodic solid cubes 12 , 13 , two-dimensional hole arrays 14 , periodic arrays of slanted grooves 15 , and gradient dielectric-filled metallic grating 16 . Furthermore, it is worth mentioning that commercial solvers (like CST eigenmode solver) are only able to calculate the frequency behaviors of the real parts of complex wave numbers, while the imaginary parts of the waves propagated in the SSPP structures cannot be displayed 17 .…”