[Paper Review] Dirac Metamaterial Assembled by Pyrene Derivative and its Topological Photonics

Kyoung Hwan Choi, Da Young Hwang+1 more|arXiv (Cornell University)|Jan 12, 2021

Metamaterials and Metasurfaces Applications49 references4 citations

TL;DR

This paper proposes a self-assembled 3D Dirac metamaterial using the pyrene derivative HYLION-12, which exhibits anisotropic polarizability and ring current. By leveraging Mie resonances and dielectric hyperbolic behavior in the ultraviolet, it demonstrates topological photonics phenomena such as Pancharatnam-Berry phase effects, wavefront shaping, and edge-mode waveguiding, achieving 142% reflectance at 242 nm and asymmetric transmittance up to 30%.

ABSTRACT

Over the past decade, topology has garnered great attention in a wide area of physics. In particular, it has exerted influence on photonics because carefully engineered photonic crystals and metamaterials can help explore the non-trivial state of materials. In this regard, all dielectric metamaterials with large anisotropy, and dipole and multipole Mie resonators have played an increasingly important role in topological photonics. Advantages of Mie resonators make it possible to quest for non-trivial states in three dimensions and theoretical calculation supports its potential. However, it is very difficult to demonstrate this experimentally because it is hard to make the metacrystal by anisotropic meta-atoms despite much effort. Here we report a Dirac metamaterial for 3D topological photonics. It is implemented by a metacrystal self-assembled by a molecule, HYLION-12 which has both anisotropic polarizability and ring current. As its peculiar properties, it has an exotic optical constant that can be used for the electric and magnetic hyperbolic metamaterial, and the double hyperbolic metamaterial in the ultraviolet region. It also showed 142% of reflectance at 242nm as an amplified reflector and asymmetric transmittance up to 30% through the opaque substrate as a Huygens source under 300nm. Furthermore, it demonstrated various phenomena of topological photonics such as Pancharatnam-Berry and waveguide phase merging, wavefront shaping and waveguide on edges as a 3D topological photonic material. The new strategy using polyaromatic hydrocarbons (PAHs) is expected to be an effective way to realize 3D topological photonics.

Motivation & Objective

• To realize three-dimensional topological photonics using all-dielectric metamaterials with non-trivial band topology.
• To overcome experimental challenges in fabricating anisotropic meta-atoms for 3D metacrystals.
• To exploit the unique optical properties of polyaromatic hydrocarbons (PAHs) for self-assembled metamaterials.
• To demonstrate topological edge states and wavefront control in a 3D photonic system using molecular self-assembly.
• To achieve enhanced optical responses such as hyperbolic behavior and Huygens-like emission in the deep ultraviolet.

Proposed method

• Utilized the pyrene-based molecule HYLION-12, which exhibits anisotropic polarizability and supports ring currents.
• Engineered a metacrystal via self-assembly of HYLION-12 molecules to form a 3D periodic structure with Mie resonances.
• Leveraged Mie resonances in dielectric meta-atoms to achieve electric and magnetic hyperbolic modes in the ultraviolet range.
• Designed the system to support double hyperbolic behavior, enabling strong anisotropy and directional wave propagation.
• Employed wavefront shaping and phase engineering to demonstrate topological edge states and Pancharatnam-Berry phase effects.
• Measured asymmetric transmittance through an opaque substrate, confirming Huygens-like source behavior under 300 nm illumination.

Experimental results

Research questions

• RQ1 Can a self-assembled molecular metamaterial support 3D topological photonics with non-trivial band topology?
• RQ2 Can pyrene-based molecules with anisotropic polarizability and ring currents enable hyperbolic behavior in the deep ultraviolet?
• RQ3 To what extent can molecular self-assembly produce functional 3D metacrystals with tunable optical responses?
• RQ4 Can such a system exhibit topological edge states and wavefront control in three dimensions?
• RQ5 What are the limits of reflectance and asymmetric transmission in a dielectric metamaterial at 242 nm?

Key findings

• The HYLION-12-based metacrystal achieved 142% reflectance at 242 nm, indicating amplified reflection beyond unity.
• Asymmetric transmittance of up to 30% was observed through an opaque substrate, confirming Huygens-like source behavior.
• The system exhibited double hyperbolic metamaterial response in the ultraviolet, enabling strong anisotropy and directional propagation.
• Topological photonics phenomena such as Pancharatnam-Berry phase effects and waveguide phase merging were experimentally demonstrated.
• Edge-mode waveguiding was observed, confirming the presence of topologically protected states in 3D.
• The self-assembled structure supported electric and magnetic hyperbolic modes, validating theoretical predictions for 3D topological photonics.