Three‐dimensional Random Dielectric Colloid Metamaterial with Giant Isotropic Optical Activity

Abstract

Motivated by the theoretical observation that isotropic chirality can exist even in completely random systems, a dielectric metamaterial consisting of a random colloid of meta-atoms is designed, which exhibits unprecedentedly high isotropic optical activity. Each meta-atom is composed of a helically arranged cluster of silicon nanospheres. Such clusters can be fabricated by large-scale DNA self-assembly techniques. It is demonstrated that the use of a high concentration of the meta-atoms in the colloid provides significant suppressions of incoherent scattering losses. As a result, the proposed system shows three orders of magnitude improvement of isotropic optical activity as compared with the previous metamaterial designs. This work highlights the significant potential of completely random systems, which are commonly produced in colloidal sciences, for applications as metamaterials toward novel photonic effects and devices.

Roadmap on electromagnetic metamaterials and metasurfaces

“…Large reduction in fabrication costs of some types of BAMMs and BAMSs can be achieved with the use of self-assembly techniques, such as DNA-origami [83]. This advance would allow creation of macroscopic devices for applications in nonlinear optics, stereochemistry, and pharmaceutical engineering.…”

Spheres of maximum electromagnetic chirality

“…However, to date, objects yielding MECh have only been unveiled in complex chiral metamaterials. For instance, in a double-turn helix [43], on metasurfaces made of pairs of dielectric bars [44], in dielectric metamaterials consisting of a random colloid of meta-atoms [45], or in a photonic crystal with a chiral array of perforating holes [46], among others [47][48][49][50][51][52]. In this regard, we should note that numerical methods are involved in all previous examples devoted to the search for objects yielding MECh [43][44][45][46][47][48][49][50][51][52].…”

“…For instance, in a double-turn helix [43], on metasurfaces made of pairs of dielectric bars [44], in dielectric metamaterials consisting of a random colloid of meta-atoms [45], or in a photonic crystal with a chiral array of perforating holes [46], among others [47][48][49][50][51][52]. In this regard, we should note that numerical methods are involved in all previous examples devoted to the search for objects yielding MECh [43][44][45][46][47][48][49][50][51][52]. This is because the constitutive relations of chiral media have only been analytically solved for the case of spherical objects by Craig Bohren in 1974 [53].…”

Magnetically Induced Terahertz Birefringence and Chirality Manipulation in Transverse‐Magnetized Metasurface

“…[8][9][10] Usually, the structures lacking the mirror plane or inversion symmetry can exhibit different optical responses to the circularly polarized (CP) light with different photonic spin chiral states of left-circular polarization (LCP) and right-circular polarization (RCP). [11][12][13] The optical chirality can be described quantitatively by the circular dichroism (CD) effect, i.e., the differential transmittance for the two spin states; and the optical activity (OA) effect, i.e., the polarization rotation of a linearly polarized (LP) light through the chiral media. [14,15] By breaking the mirror symmetry in the geometry, chiral metasurfaces with artificial electromagnetic chirality can be achieved, which provides new opportunities for THz chiral materials and devices.…”