Large‐Area 3D‐Printed Chiral Metasurface Composed of Metal Helices

Abstract

of semiconductor technology, such as consecutive lithographic steps with layers alignment, and the deposition and chemical etching of materials, are used. Besides, for preventing the capillary sticking of 3D microstructures and nanostructures, special treatments of surfaces and the supercritical drying technique are used after liquid-etching and resistdevelopment steps. [15,16] In ref.[17], a method was proposed for fabrication of microhelices and nanohelices from elastically strained thin semiconductor strips detached, with the help of selective etching of a sacrificial layer, from the substrate and then rolled in classically shaped 3D helices. The latter approach, combined with supercritical drying, [16] was successively employed for forming, on a GaAs substrate, a chiral metamaterial in the form of a single-layer array of 14.5 µm diameter 3D microhelices fabricated from a strained hybrid semiconductor-metal (In 0.2 Ga 0.8 As/GaAs/Ti/Au) films. [18,19] It was shown that the maximum polarization-plane rotation angle for terahertz radiation having passed the heliceson-substrate system reached 17° at 2.1 THz frequency. A close value for the polarization-plane rotation angle of terahertz radiation, 14°, was also obtained using a structure that involved 3D metal gammadion-shaped elements located directly on the surface of pyramidal trenches etched in a silicon substrate. [20] Experimental data obtained for both chiral metamaterials proved a high effectiveness of the interaction of electromagnetic radiation with the 3D conducting microresonators, thus encouraging the workers to spent further efforts on the search for simpler and cheaper technological solutions.Today, rapid progress in the development of additive technologies [21,22] opens up wide opportunities in the field of 3D chiral resonator elements, 3D metamaterials, and photonic crystals. [23][24][25] A number of sequential 3D printing methods have enabled the point-by-point formation of free-standing conducting helices for chiral metamaterials active in a broad range of radiation wavelengths, from microwave (MW) to optical frequencies. Those methods can be classed to several groups. First, these are methods including the electrochemical and chemical deposition of metals onto the surface of printed 3D polymer structures: i) filling of helically shaped channels with a metal [9,26] and ii) covering of free-standing 3D helical microcarcasses with a metal. [27] Second, this is the growth of An original design for chiral metasurfaces formation is proposed. The hybrid fabrication approach is based on the 3D printing of polymer substrates with a shape-generating "helical" relief, molding, and subsequent shadow metal deposition. The formed double-layer grating of multiturn metal helices rotates the polarization plane of sub-terahertz and microwave radiation through an angle in excess of 40°. Both experimentally and in numerical simulations, it is demonstrated that re-reflection phenomena occur in the "metal helixpolymer substrate" hybrid structure. Those phenomena per...

An introduction of perovskite materials in chiral metasurfaces

“…The chiral designs may be extrinsic or intrinsic, exhibiting optical activity or circular dichroism, defined as the rotation of the polarization plane or difference of optical output for two differently polarized lights. Strong chiro-optical responses have been found for various structures such as L-shaped [16], g-shaped [19], X-shaped, Zshaped [20], spiral-shaped, gammadion-shaped [21], helices [22], twisted arcs [23] and semicircles [24], as shown in Figure 1. The chiral objects are optically characterized by birefringence (optical activity) and circular dichroism (CD) [25], meaning one of the polarizations is perfectly absorbed.…”

Bio-Inspired Micro- and Nanorobotics Driven by Magnetic Field

“…This microscopic effect emulates “Venetian blinds” and leads to dynamic changes in the optical properties of the investigated structures in real time. In the field of designing structurally defined colors, considerable success has been achieved owing to the use of bioinspired structures, which are based on the phenomenon of Bragg diffraction [ 157 , 158 , 159 , 160 ]. In addition, a number of biomimetic non-magnetic photonic structures have been created, including artificial opals and lamellar interference structures of the butterfly-wing type [ 161 , 162 , 163 , 164 ].…”

Versatile Cross‐Polarization Conversion Chiral Metasurface for Linear and Circular Polarizations

“…In the past decade, chiral metasurfaces (CMS), which show circular dichroism, asymmetric transmission and polarization rotation in the polarization domain, [27][28][29] have attracted an enormous study interest. [30][31][32][33][34] Various types of meta-atoms (unit cells), for instance, the cross slot, [30] the via connected double-layer slot, [35] the V-shaped slot, [36] the Z-shaped resonator, [37] the T-shaped resonator, [38] the electric field-coupled resonator, [39,40] the split ring resonator [41][42][43][44] and the split-ring spiral [45] have been reported and implemented in the design of XPCs. Due to the high Q nature of CMS, such devices usually function in a limited bandwidth.…”

“…The meta-atom is square in shape and placed one next to another in both x and y directions. The periods along the x and y directions are equal to the side length l. In the closely arranged metasurface, the resonant frequency is related to the period l. [28,33] In this design, l is chosen to be 4.12 mm, which is approximately equal to λ0/2, where λ0 is the wavelength at 35.5…”