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Extrinsic 2D chirality: giant circular conversion dichroism from a metal-dielectric-metal square array
Tun Cao1, Chenwei Wei1, Libang Mao1
1Department of Biomedical Engineering, Dalian University of Technology, China (P.R.C.).
Scientific Reports
|December 16, 2014
Summary
Researchers demonstrate a novel method for achieving strong chiroptical responses using 2D chirality in multilayer metamaterials (MMs). This approach avoids complex structures, enabling giant circular conversion dichroism (CCD) without intricate designs.
Area of Science:
- Metamaterials
- Chirality
- Plasmonics
Background:
- Giant chiroptical responses are typically observed in complex 3D chiral metamaterials (MMs).
- Fabricating subwavelength chiral structures for optical applications presents significant challenges.
- Alternative methods for achieving strong chiroptical effects are needed.
Purpose of the Study:
- To propose a new paradigm for achieving strong circular conversion dichroism (CCD).
- To demonstrate that extrinsic 2D chirality in multilayer achiral MMs can yield giant chiroptical responses.
- To show that complex structures are not necessary for strong chiroptical effects.
Main Methods:
- Design of a multilayer achiral metamaterial structure.
- The structure comprises an array of thin gold (Au) squares separated by a GaAs dielectric layer from a continuous Au film.
- Investigation of the chiroptical response under oblique incidence in the mid-infrared (M-IR) region.
Main Results:
- A pronounced extrinsically 2D-chiral effect, specifically circular conversion dichroism (CCD), was observed.
- The 2D-chiral effect arises from the interplay between the Au squares array and the incident light's propagation direction.
- A large CCD magnitude was achieved due to significant differences in reflectance conversion efficiencies for left- and right-circularly polarized light.
Conclusions:
- Giant chiroptical responses can be achieved using extrinsic 2D chirality in multilayer achiral metamaterials.
- This approach offers an alternative to complex 3D chiral structures for generating strong chiroptical effects.
- The proposed structure is effective for mid-infrared applications.
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