Applications brief: Experimental demonstration of the microscopic origin of circular dichroism in two-dimensional metamaterials

Key points


  • AFM-IR and s-SNOM have been used in combination to probe the role of chirality in the circular dichroism observed in nanoscale 2D metasurfaces
  • By accessing both the radiative (s-SNOM) and non-radiative (AFM-IR) information on plasmonics structures, unique and complementary plasmonic properties can be obtained.
  • s-SNOM is used to map the optical energy distribution of 2D metasurfaces.
  • AFM-IR is used to detect the Ohmic heating in the structure.
  • For the first time, it has been conclusively established the circular dichroism observed in 2D metasurfaces is attributed to handedness dependent Ohmic heating.

Key words

AFM-IR | s-SNOM | Plasmon, Metasurfaces | Circular Dichroism | Ohmic Heating

Authors

A. B. Khanikaev, N. Arju, Z. Fan, D. Purtseladze, F. Lu, J. Lee, P. Sarriugarte, M. Schnell, R. Hillenbrand, M. A. Belkin & G. Shvets

Abstract

Optical activity and circular dichroism are fascinating physical phenomena originating from the interaction of light with chiral molecules or other nano objects lacking mirror symmetries in three-dimensional (3D) space. While chiral optical properties are weak in most of naturally occurring materials, they can be engineered and significantly enhanced in synthetic optical media known as chiral metamaterials, where the spatial symmetry of their building blocks is broken on a nanoscale. Although originally discovered in 3D structures, circular dichroism can also emerge in a two-dimensional (2D) metasurface. The origin of the resulting circular dichroism is rather subtle, and is related to non-radiative (Ohmic) dissipation of the constituent metamolecules. Because such dissipation occurs on a nanoscale, this effect has never been experimentally probed and visualized. Using a suite of recently developed nanoscale-measurement tools, we establish that the circular dichroism in a nanostructured metasurface occurs due to handedness-dependent Ohmic heating.

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