Optical and Infrared Helical Metamaterials

Abstract

By tailoring metamaterials with chiral unit cells, giant optical activity and strong circular dichroism have been achieved successfully over the past decade. Metamaterials based on arrays of metal helices have revolutionized the field of chiral metamaterials, because of their capability of exhibiting these pronounced chiro-optical effects over previously unmatched bandwidths. More recently, a large number of new metamaterial designs based on metal helices have been introduced with either optimized optical performance or other chiro-optical properties for novel applications. The fabrication of helical metamaterials is, however, challenging and even more so with growing complexity of the metamaterial designs. As conventional two-dimensional nanofabrication methods, for example, electron-beam lithography, are not well suited for helical metamaterials, the development of novel three-dimensional fabrication approaches has been triggered. Here, we will discuss the theory for helical metamaterials and the principle of operation. We also review advancements in helical metamaterial design and their limitations and influence on optical performance. Furthermore, we will compare novel nano-and microfabrication techniques that have successfully yielded metallic helical metamaterials. Finally, we also discuss recently presented applications of helical metamaterials extending beyond the use of far-field circular polarizers.

Direct laser printing of chiral plasmonic nanojets by vortex beams

“…Artificially designed nanoscale chiral-shaped structures, mimicking their natural analogues owing to unique ways of interaction with optical radiation, possess remarkable properties as circular dichroism, enhancement of nonlinear signals, highly directional emission and photoactivity [1][2][3][4]. Meanwhile, utilization of state-of-the-art direct nanofabrication techniques based on ion-or electron beam milling for chiral nanostructures fabrication is rather challenging, which triggers, in its turn, search for novel pathways to produce such unique nanostructures.…”

New Twists of 3D Chiral Metamaterials

“…[2] However, the idea of rationally designed artificial crystals got a tremendous boost when magnetic composites based on split-ring resonators were discussed theoretically in 1999 and realized experimentally in 2000. [6,7] Today, the field of metamaterials has become very broad, encompassing nearly all aspects of solids, including optical, electrical, magnetic, thermal, and mechanical properties-linear and nonlinear as well as static and dynamic. [5] Thereafter, the field of metamaterials has strongly benefitted from advances in nanotechnology and 3D additive manufacturing of complex chiral architectures that would be hard or impossible to make by other means.…”

“…In this research news, to avoid repetition, we build on extensive previous review articles by us and others on chiral optical metamaterials [7,11,12] as well as on reviews on mechanical metamaterials in general. Each unit cell is composed of a large number of atoms.…”

Chiroptically Active Metallic Nanohelices with Helical Anisotropy

“…Plasmonic helices with a P in the micro‐scale, i.e., plasmonic microhelices, have been demonstrated to function as circular polarizers with minimized polarization conversion and circular polarization converters, in the mid‐infrared range. The chiroptical theory and functional operation principles of plasmonic microhelices have been reviewed currently …”

“…The chiroptical theory and functional operation principles of plasmonic microhelices have been reviewed currently. [13] Circular polarization manipulation in the ultraviolet (UV)visible-near infrared (NIR) region attracts an increasing attention, due to an intensive desire for advanced optical display and chirality-determined bio-applications. To operate the optical manipulation, it is physically necessary to make P shrink below the micro-scale, that is, the fabrication of nanohelices (NHs).…”