Exploiting Colloidal Metamaterials for Achieving Unnatural Optical Refractions

Ji Hyeok Huh, Kwangjin Kim, Eunji Im, Jaewon Lee, Yong Deok Cho, Seungwoo Lee

Research output: Contribution to journalReview articlepeer-review

Abstract

The scaling down of meta-atoms or metamolecules (collectively denoted as metaunits) is a long-lasting issue from the time when the concept of metamaterials was first suggested. According to the effective medium theory, which is the foundational concept of metamaterials, the structural sizes of meta-units should be much smaller than the working wavelengths (e.g., << 1/5 wavelength). At relatively low frequency regimes (e.g., microwave and terahertz), the conventional monolithic lithography can readily address the materialization of metamaterials. However, it is still challenging to fabricate optical metamaterials (metamaterials working at optical frequencies such as the visible and near-infrared regimes) through the lithographic approaches. This serves as the rationale for using colloidal self-assembly as a strategy for the realization of optical metamaterials. Colloidal self-assembly can address various critical issues associated with the materialization of optical metamaterials, such as achieving nanogaps over a large area, increasing true 3D structural complexities, and cost-effective processing, which all are difficult to attain through monolithic lithography. Nevertheless, colloidal self-assembly is still a toolset underutilized by optical engineers. Here, the design principle of the colloidally self-assembled optical metamaterials exhibiting unnatural refractions, the practical challenge of relevant experiments, and the future opportunities are critically reviewed.

Original languageEnglish
Article number2001806
JournalAdvanced Materials
Volume32
Issue number51
DOIs
Publication statusPublished - 2020 Dec 22

Keywords

  • capacitive coupling
  • colloids
  • magnetism
  • metamaterials
  • self-assembly

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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