Tailoring Light with Layered and Moiré Metasurfaces

Abstract

Optical metasurfaces are assemblies of subwavelength, artificially designed inclusions forming planarized devices with unprecedented capabilities to manipulate electromagnetic waves and facilitate multiple functionalities. Recent topical efforts in this research area have been focused on pushing forward the frontiers of enhanced light-matter interactions exploiting new concepts and fabrication capabilities. In this context, layered and twisted metasurfaces have showcased interesting features, including flexibility and tunability in manipulating light, contributing to the development of moiré physics for light. Here, we provide an overview on the state-of-art layered and stacked moiré metasurfaces. Freespace multifunctional metadevices are first discussed, followed by recent discoveries in polaritonics and twistronics for twisted hyperbolic metasurface bilayers. We conclude with a discussion on recent advances in the nanofabrication of moiré metasurfaces and remark on their future potential applications. Emerging Strategies for Advanced Optical Metasurfaces Using Twisting and StackingOptical metasurfaces (see Glossary), commonly recognized as the 2D counterpart of bulk metamaterials, are composed of subwavelength planarized inclusions [1,2]. Unlike metamaterials, metasurfaces usually have a thickness smaller than the operational wavelength in free space, holding the promise for next-generation multifunctional, compact, and integrated functional optical devices. Their ultrathin nature can significantly ease nanofabrication requirements compared with metamaterials, making them compatible for mass production in the semiconductor industry. One essential step in designing metasurfaces is to control light interactions with its local functional composites, so-called meta-atoms, thus enabling unprecedented control of the local scattering processes in terms of phase, amplitude, polarization, frequency, dispersion, and more [3][4][5][6]. In this way, a designer metasurface can be endowed with unprecedented control in tailoring the impinging light. This process inherently requires resonant light-matter interactions in meta-atoms, given the small light-matter interaction length. Tremendous efforts have been made in searching for better materials and novel metasurface designs for improved performance. For composite materials, metals can support enhanced photonic local density of states due to plasmonic phenomena, but may suffer from large Ohmic loss [7][8][9]. On the contrary, all-dielectric materials have significantly lower loss, but typically require a larger thickness, in the order of the wavelength in the material, limiting the field localization and enhancement of light-matter interactions [10]. Various geometries have been explored to realize metasurfaces, including split ring resonators, nanorods, and V-shape nanoantennas, supporting optical resonances in subwavelength meta-atoms [7,10]. These designs typically rely on heavy optimization techniques to obtain the best responses, requiring computational resources and tim...

Chiral plasmonic nanostructures: recent advances in their synthesis and applications

“…[51][52][53][54][55][56][57][58][59][60] It is nevertheless much more difficult to prepare complex chiral assemblies with a hierarchical arrangement of the building blocks using top-down approaches. 61 One representative example of such materials is the twisted multilayer structure composed of aligned gold nanorods developed by Y. Zhao et al (Fig. 2C).…”

Hyperbolic metamaterials: fusing artificial structures to natural 2D materials

“…Lastly, those hyperbolicities are intrinsically bounded by pristine forms of material candidates and hence have fixed working frequency ranges, which impose a limit on the working frequency ranges of various exciting applications. Further application of the philosophy of metamaterials, i.e., to mold electromagnetic responses by engineering sub-wavelength structures, could yield architectures of natural hyperbolic materials that induce exotic wave phenomena, such as infrared HMSs in nanostructured hBN [66,67], topological polaritons in twisted ( -MoO 3 ) bilayers [217], stacked multilayers for heterostructures [65,128,[229][230][231][232], and others [233].…”

Tunable circular dichroism through absorption in coupled optical modes of twisted triskelia nanostructures

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