All-metal self-supported THz metamaterial – the meta-foil

Abstract

Modern metamaterials face functional constraints as they are commonly embedded in or deposited on dielectric materials. We provide a new solution by microfabricating a completely free-standing all-metal self-supported metamaterial. Using upright S-string architecture with the distinctive feature of metallic transverse interconnects, we form a locally stiff, globally flexible space-grid. Infrared Fourier transform interferometry reveals the typical double-peak structure of a magnetically excited left-handed and an electrically excited right-handed pass-band that is maintained under strong bending and heating, and is sensitive to dielectrics. Exploiting UV/X-ray lithography and ultimately plastic moulding, meta-foils can be mass manufactured cost-effectively to serve as optical elements.

3D THz metamaterials from micro/nanomanufacturing

“…Process materials like substrates, resists, and sputter targets should be readily available. State-of-the-art experimental devices were made primarily from -primary pattern generation including direct writing by means of electron, laser, and ion beams [13,41] -UV or X-ray lithography (LIGA) [11,13,15,16,19] -Nanoimprint lithography [50] -Interferometric lithography enhanced by other process steps [14,51] -direct laser writing exploiting two-photon-absorption in resist [44][45][46] -directional evaporation and deposition [47] -electroplating in porous alumina templates [48] -self-rolling of strained layers [52]. Furthermore, Moser et al proposed plastic molding of metamaterials, in particular, of the meta-foil [53].…”

“…Starting from a constant refractive index meta-foil [19], Moser and collaborators have worked out a concept to include a spatial variation of the refractive index across a constant-thickness meta-foil [76] to achieve more sophisticated optical functions than with a slab, such as prism-like deflection and dispersion or lens-like focusing/defocusing starting, for simplicity, with cylindrical lenses. Furthermore, even more complex functions seem possible that use arbitrary index distributions.…”

“…O. Moser and C. Rockstuhl: 3D THz metamaterials from micro/nanomanufacturing caused by a dielectric added to a free-standing all-metal metamaterial was described in [19]. An upper bound of the sensitivity achieved was 1.1 THzcm 3 /g of PMMA soaked into the meta-foil [49,105].…”

“…Present day electromagnetic metamaterials in the THz range usually come as composite materials with micro/nanometer range metallic elements, the so-called inclusions, embedded in a plastic matrix or deposited on a dielectric substrate. Figure 1 shows a few selected samples of metamaterials starting with the original GHz rod-splitring materials designed and realized by Pendry et al [8], Smith et al [9,10], and extending to near infrared and optical frequencies [11][12][13][14][15][16][17][18][19][20]. Furthermore, latest developments like the free-standing bi-layer chip [15,16] and, more so, the meta-foil [19] rely on completely self-supported metamaterials that do no longer need matrices or substrates, thus avoiding constraints of their functionality due to dielectric host materials.…”

“…Present-day fabrication methods typically produce layers of metamaterials which are then stacked to multilayers. This is a common approach for primary pattern generation [41,42] as well as for lithography [15,16,19]. A few layers are commonly sufficient to develop the full electromagnetic effect.…”