Free-standing THz electromagnetic metamaterials

Abstract

Using micromanufactured S-shaped gold strings suspended in free space by means of window-frames, we experimentally demonstrate an electromagnetic meta-material (EM(3)) in which the metallic structures are no longer embedded in matrices or deposited on substrates such that the response is solely determined by the geometrical parameters and the properties of the metal. Two carefully aligned and assembled window-frames form a bi-layer chip that exhibits 2D left-handed pass-bands corresponding to two different magnetic resonant loops in the range of 1.4 to 2.2 THz as characterized by Fourier transform interferometry and numerical simulation. Chips have a comparably large useful area of 56 mm(2). Our results are a step towards providing EM(3) that fulfill the common notions of a material.

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].…”

“…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.…”

Singapore Synchrotron Light Source

“…The world's first bi-layer chips of 2.2 THz EM 3 were built and spectrally characterized at ISMI (Figure 3 (right)) [10][11][12]. ISMI also served for a microspectroscopic study of explosives RDX, PETN, and TNT in the fingerprint region (400-4000 cm −1 ), which showed that explosives can be unambiguously determined from their post-blast residues, the brilliance of synchrotron radiation enhancing sensitivity and spatial resolution [13].…”

Terahertz metamaterials and systems based on rolled-up 3D elements: designs, technological approaches, and properties

“…Metamaterials are at the stage of active development61023. The development scheme of THz and optical metamaterials can be outlined as the progress from metamaterials with planar resonators81424252627, to multilayer resonators and metamaterials282930, then to metamaterials with 3D resonators313233, and, finally, to various systems and devices101634 based on such metamaterials. Nowadays, metamaterials for THz and optical ranges are mainly fabricated by planar patterning technologies.…”