Terajets produced by dielectric cuboids

Abstract

The capability of generating terajets using 3D dielectric cuboids working at terahertz (THz) frequencies (as analogues of nanojets in the infrared band) are introduced and studied numerically. The focusing performance of the terajets are evaluated in terms of the transversal full width at half maximum along x-and y-directions using different refractive indexes for a 3D dielectric cuboid with a fixed geometry, obtaining a quasi-symmetric terajet with a subwavelength resolution of ~0.46λ0 when the refractive index is n = 1.41. Moreover, the backscattering enhancement produced when metal particles are introduced in the terajet region is demonstrated for a 3D dielectric cuboid and compared with its 2D counterpart. The results of the jet generated for the 3D case are experimentally validated at sub-THz waves, demonstrating the ability to produce terajets using 3D cuboids.

All-dielectric periodic terajet waveguide using an array of coupled cuboids

“…4, it can be observed that the maximum value is obtained for the first cube while it is reduced for the rest. For this chain, the power enhancement (defined as the power at the output surface of each cube compared with the power without cubes) is 8.5, 11.6 and 10.8 (in linear scale) for the first, second and third cube, respectively, in good agreement with the results of a single cuboid 20 . Thus, it is observed that a mesoscale dielectric cube-air-chain waveguide is mainly characterized by the periodicity of jets corresponding to the optimal length of air-gap between cubes when a fixed geometry and materials respectively.…”

“…These results are not surprising since a change in  modifies the refractive index of the cubes and therefore a shift of the focus should occur 20 . Also the length of terajet is increased when increasing the loss tangent.…”

“…By using these structures, the capability to produce jets at terahertz (THz) and sub-THz frequencies (so-called terajets, analog of photonic jet in optics) has been recently proposed and demonstrated experimentally by using 2D and 3D dielectric cuboids. 20,21 In this communication, the capability to produce periodically induced terajets along a chain of mesoscale 3D dielectric cubes (here, at difference with our previous works we use regular hexahedrons) separated with air-gaps of different length is numerically studied. Numerical results demonstrate that the optimum air-gap length is 2.5 0 .…”

“…The results here presented may be directly scaled to other frequency bands such as optical frequencies. All the numerical results were performed using the Finite Integration Technique with the transient solver of the commercial software CST Microwave Studio TM with the same boundary conditions and mesh as in [20][21][22] .…”

Enhancement of spatial resolution of terahertz imaging systems based on terajet generation by dielectric cube

“…23,24 The initial studies on terajet generation were based on spheroids and the well-known Mie scattering theory. 20,25,26 Later, researchers found out-both theoretically and experimentally-that cuboids can generate terajets 27 with some advantages over spheroid-generated terajets from the point of view of the imaging application, such as more symmetric hotspots. 23 The generation of terajets from the cuboid under planar illumination, which can be considered as an NA = 0 focusing device with the focal point at infinity, has been experimentally confirmed and verified in the THz frequency band; the obtained FWHM was 0.6λ.…”