Novel phenomena in planar and layered, photonic and microwave metamaterials

Abstract

This work is related to the investigation and development of novel concepts to utilise planar nanostructures in optics, aided by complementary research in the microwave domain—in particular: Strong polarisation conversion capabilities are shown for planar chiral nanoholes in the near-infrared part of the spectrum. The efficiency is found to depend strongly on the mutual orientation of the chiral hole and the polarisation of the incident light.
Polarisation-dependent nano-focusing is seen for these nanoholes. Light is concentrated to a spot size of 42% of the wavelength in the proximity of a nanohole. Broken enantiomeric symmetry is discovered for planar chiral structures excited with circularly polarised light, it is explained numerically and analytically for optics. Non-paraxial contributions are analytically proven to be crucial to the description of the nonlocal response of planar chiral structures. Asymmetric optical transmission in anisotropically nanostructured planar chiral metamaterials is demonstrated, for the first time. This phenomenon is mediated by a new type of excitation: an enantiomerically sensitive plasmon. The normal incidence transmission of circularly polarised light displays a difference exceeding 25% for opposite propagation directions. Giant gyrotropy in bilayered chiral structures is shown for both optical and microwave spectral regions, for the first time. The maximum relative polarisation rotatory power in the microwave domain is found to be 5 orders of magnitude stronger than in a gyrotropic crystal of quartz; for optical frequencies it exceeds 2500 °/mm. The first demonstration of an optical magnetic mirror is reported. The phase change for the electric field of a wave reflected by a nanostructured metal surface is found to be smaller than 90° (the signature of magnetic mirror behaviour) for a broad spectral range from 550 to 750 nm, reaching values below 25°. A unit of planar chirality is proposed, for the first time. Normalisation procedures for the class of triple-integrated and -summated measures of planar chirality are introduced. A new type of multiplicative measure is defined and its properties and applicability are demonstrated. A process for nanoimprint lithography at room temperature is developed. The production of planar chiral metamaterials for optical applications is validated to be reliable and reproducible and to provide a strong polarisation effect.

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Identifiers

ORCID for Nikolai Zheludev: orcid.org/0000-0002-1013-6636

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