Wave manipulation with magnetically tunable metasurfaces

Abstract

Tunable metasurfaces have emerged as an efficient approach to manipulate the wave propagation. Different from previous work concentrating on electrically tunable mechanisms, here we demonstrate a magnetically tunable metasurface composed of ferrite rods and metallic foils. By tuning the thickness of ferrite rods, metasurfaces with different rod thickness gradients are obtained. The incident wave can propagate through the metasurfaces due to the extraordinary transmission. The deflection angle of the transmission wave is not only influenced by the rod thickness gradient, but also tuned by the applied magnetic field. This approach opens a way for the design of tunable metasurfaces.Manipulation of electromagnetic (EM) waves (e.g., for phase modulation, light absorption, and imaging applications) has long been restricted by the limited range of EM parameters among natural materials. Electromagnetic metamaterials are composites in which subwavelength features, rather than the natural ones, control the macroscopic electromagnetic properties 1-3 . The unique metamaterial structure makes it possible to achieve considerable electromagnetic response by just using a slab of metamaterial which is much thinner than a wavelength 4 . Metasurface is an ultrathin planar metamaterial comprising artificially designed arrays of subwavelength resonating units, which has attracted significant interests in the optics community 5,6 . The key point for metasurface is to use resonating unit arrays with subwavelength separation and spatially varying geometric parameters (for example, resonating unit shape, size, orientation) to induce a spatially varying optical response, especially the abrupt changes to the phase and amplitude of the incident wave 7-10 . Therefore, they offer much more opportunities for the control of EM waves than traditional materials.Recently, several kinds of metasurfaces have been designed and many interesting phenomena have been exploited [11][12][13][14] . A metasurface made of "v-shaped" antennas can realize anomalous reflection/refraction of impinging light, which cannot be explained by the classical Snell's law 15 . Another metasurface perforated with an array of coaxial annular apertures obtained highly efficient beam steering. In spite of the aboved achievements on metasurfaces, the realization of high performance metasurface-based devices still remains a great challenge due to very limited tuning ranges and modulation depths. Great efforts have been paid in developing tunable metasurfaces 16,17 . Yao et al. demonstrated electrically tunable metasurface absorbers with strong light modulation effect by incorporating a metasurface on graphene into an asymmetric Fabry−Perot resonator 18 . Ee et al. proposed a mechanically reconfigurable metasurface by fabricating Au nanorod arrays on a stretchable polydimethylsiloxane substrate 19 . The anomalous refraction angle induced by such a metasurface can be adjusted from 11.4° to 14.9° by stretching the substrate by 30%. It is well known that, besides the electrically a...

Tunable/Reconfigurable Metasurfaces: Physics and Applications

“…In conclusion, we have briefly summarized recent exciting progress on tunable/reconfigurable metasurfaces with meta-atoms controlled both uniformly and individually by different types of external knobs, focusing particularly on available tuning mechanisms and potential applications of realized metadevices. These research outputs have offered metasurfaces significantly expanded capabilities to control EM waves in different frequency regimes, providing a promising platform to realize functional devices meeting different applications, such as SLMs [33, 36, 121, 122], switchable color filter [123], tunable metalenses [53, 96, 124], and polarization controller [31, 41]. However, although tunable metadevices can bring expanded controllability on EM waves, they inevitably exhibit certain disadvantage as compared to passive ones.…”

Toward Intelligent Metasurfaces: The Progress from Globally Tunable Metasurfaces to Software‐Defined Metasurfaces with an Embedded Network of Controllers

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Electromagnetic Control by Actuating Kirigami-Inspired Shape Memory Alloy: Thermally Reconfigurable Antenna application

“…Optical control is normally as fast as electrical, but the short wavelength makes it difficult to implement. Magnetic methods use magnetic material, e.g., ferrite, to control RF properties by controlling DC bias or magnetic field using a magnetic tensor [ 13 , 14 ]. However, magnetic approaches require bulky and difficult to control components.…”