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The lattice geometry of natural materials and the structural geometry of artificial materials are crucial factors determining their physical properties. Most materials have predetermined geometries that lead to fixed physical characteristics. Here, the demonstration of a carbon nanotube network serves as an example of a system with controllable orientation achieving on‐demand optical properties. Such a network allows programming their optical response depending on the orientation of the constituent carbon nanotubes and leads to the switching of its dielectric tensor from isotropic to anisotropic. Furthermore, it also allows for the achievement of wavelength‐dispersion for their principal optical axes – a recently discovered phenomenon in van der Waals triclinic crystals. The results originate from two unique carbon nanotubes features: uniaxial anisotropy from the well‐defined cylindrical geometry and the intersection interaction among individual carbon nanotubes. The findings demonstrate that shaping the relative orientations of carbon nanotubes or other quasi‐one‐dimensional materials of cylindrical symmetry within a network paves the way to a universal method for the creation of systems with desired optical properties. [ABSTRACT FROM AUTHOR]

The development of technology for integrating optical metaresonators with two-dimensional and layered van der Waals (vdW) materials opens up broad prospects for the creation of subdiffraction concentrators of electromagnetic energy, surface-emitting lasers, laser displays, and highly efficient nonlinear converters. In this work, we develop a straightforward strategy for the design and fabrication of surface-emitting laser devices based on few-layer transition metal dichalcogenides placed on the dielectric metasurfaces in the regime of quasi-trapped mode excitation. We optimize the parameters of MoTe2 flake and Si metasurface to achieve a positive feedback and to observe the lasing, resulting from their integration, with the predicted characteristics. Promising potential for the development of vdW-metalaser platform is associated with the possibility of simple polarization control of lasing regimes by employing the features of the bianisotropic response of the metasurface's building blocks. [ABSTRACT FROM AUTHOR]

Chirality is one of the most mysterious symmetry transformations. Very readily broken in biological systems, it is practically absent in naturally occurring inorganic materials and is very challenging to create artificially. Chiral optical wavefronts are often used for the identification, control, and discrimination of left‐ and right‐handed biological and other molecules. Thus, it is crucially important to create materials capable of chiral interaction with light, which would allow one to assign arbitrary chiral properties to a light field. This study utilizes van der Waals technology to assemble helical homostructures with chiral properties (e.g., circular dichroism). Because of the large range of van der Waals materials available, such helical homostructures can be assigned with very flexible optical properties. The approach is demonstrated by creating helical homostructures based on multilayer As2S3${\rm As}_2{\rm S}_3$ (arsenic trisulfide), which offers the most pronounced chiral properties even in thin structures due to its strong biaxial optically anisotropy. The work showcases that the chirality of an electromagnetic system may emerge at an intermediate level between the molecular and the mesoscopic one due to the tailored arrangement of non‐chiral layers of van der Waals crystals and without additional patterning. [ABSTRACT FROM AUTHOR]

The growing family of two-dimensional crystals has been recognized as a promising platform for investigation of rich low-dimension physics and production of a variety of devices. Of particular interest are recently reported atomic sheets of non-van der Waals materials, which reshape our understanding of chemical bonds and enable heterostructures with novel functionality. Here, we study the structural and optical properties of ultrathin non-van der Waals InGaS3 sheets produced by standard mechanical cleavage. Our ab initio calculations reveal weak out-of-plane covalent bonds, responsible for the layered structure of the material. The energy required for isolation of a single layer is as low as ~50 meVÅ–2, which is comparable with the conventional van der Waals material's monolayer isolation energies of 20–60 meVÅ–2. A comprehensive study of the structural, vibrational, and optical properties of the material reveals its wide bandgap (2.73 eV), high refractive index (>2.5) and negligible losses in the visible and infrared spectral ranges. These properties make it a perfect candidate for visible-range all-dielectric nanophotonics. [ABSTRACT FROM AUTHOR]