Deflecting and changing the direction of propagation of electromagnetic waves are needed in multiple applications, such as in lens–antenna systems, point-to-point communications and radars. In this realm, metamaterials have been demonstrated to be great candidates for controlling wave propagation and wave–matter interactions by offering manipulation of their electromagnetic properties at will. They have been studied mainly in the frequency domain, but their temporal manipulation has become a topic of great interest during the past few years in the design of spatiotemporally modulated artificial media. In this work, we propose an idea for changing the direction of the energy propagation of electromagnetic waves by using time-dependent metamaterials, the permittivity of which is rapidly changed from isotropic to anisotropic values, an approach that we calltemporal aiming. In so doing, here, we show how the direction of the Poynting vector becomes different from that of the wavenumber. Several scenarios are analytically and numerically evaluated, such as plane waves under oblique incidence and Gaussian beams, demonstrating how proper engineering of the isotropic—anisotropic temporal function of ε_r(t) can lead to a redirection of waves to different spatial locations in real time.

Metamaterials are mostly designed in the time‐harmonic scenario where wave propagation can be spatially manipulated. Tailoring the electromagnetic response of media in time has also gained the attention of the scientific community in order to achieve further control on wave‐matter interaction both in space and time. In the present work, a temporally effective medium concept in metamaterial is theoretically investigated as a mechanism to create a medium with a desired effective permittivity. Similar to spatially subwavelength multilayered metamaterials, the proposed “temporal multilayered”, or “multistepped” metamaterial, is designed by alternating in time the permittivity of the medium between two values. In so doing, the temporally periodic medium can be modeled as an effective metamaterial in time with an effective permittivity initiated by a step function. The analogy between the temporal multistepped and the spatial multilayered metamaterials is presented demonstrating the duality between both domains. The proposed temporal metamaterial is analytically and numerically evaluated showing an excellent agreement with the designed parameters. Moreover, it is shown how the effective permittivity can be arbitrarily tailored by changing the duty cycle of the periodic temporal metamaterial. This performance is also connected to the spatial multilayer scenario in terms of the filling fraction of the different materials used to create the multilayered structures.

Controlling amplitude, phase, and polarization of electromagnetic (EM) waves is key for a full manipulation of wave-matter interactions. The Brewster angle is one of the important features in this context. Here, we exploit metamaterial concepts with a time-modulated permittivity to propose the temporal equivalent of the spatial Brewster angle, a concept we call temporal analogue/equivalent of the Brewster angle. We consider temporal boundaries (as the temporal equivalent of the spatial boundaries between two media) by rapidly changing the permittivity of the medium where a wave travels from isotropic to an anisotropic permittivity tensor. It is theoretically shown that, when the incidence angle coincides with that of the temporal analogue of the Brewster angle, a forward (temporal transmission) wave is produced, while the backward (temporal reflection) is eliminated. We provide a closed-form analytical expression of the temporal analogue of the Brewster angle and demonstrate its performance both theoretically and numerically. Our findings may provide a fresh view on how to control EM wave propagation and wave-matter interactions in real time using temporal metamaterials.

The capability of generating terajets using three-dimensional (3D) dielectric cuboids working at terahertz (THZ) frequencies (as analogues of nanojets in the infrared band) is introduced and studied numerically. The focusing performance of the terajets is evaluated in terms of the transversal full width at half maximum (FWHM) along x- and y-directions using different refractive indices 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 two-dimensional (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.