Chalcogenide platforms for photonic metamaterials

Abstract

Photonic metamaterials - media artificially structured at the nanometre scale - provide extraordinary optical properties not found in nature. In this work I explored opportunities provided by changes of complex optical properties of chalcogenide alloys related to compositional variation and structural phase change to develop switchable and tunable plasmonic and dielectric metamaterials:

• I have systematically explored the properties of Bi:Sb:Te across UV to near infrared wavelengths through combinatorial high-throughput mapping techniques for the widest compositional spread reported so far. This study reveals that Bi:Sb:Te has better plasmonic properties than gold at wavelengths below 580 nm and silver below 365 nm; ability to support dielectric (Mie) resonances better than oxides at telecommunication wavelengths beyond 1200 nm; epsilon-near-zero properties across UV to IR wavelengths; sub-unity refractive index (down to 0.7) in the UV and the highest refractive index in the near-IR (up to 11.5 at 1680 nm) reported so far to our knowledge.

• I have studied for the first time the plasmonic character of amorphous Bi:Te and developed resonant optical metasurfaces based on this alloy that present strong, period-dependent plasmonic absorption resonances (QMax = 7.5) in the visible range. Furthermore, I have investigated changes of optical properties of this alloy upon structural phase change from amorphous to crystalline phases.

• I have studied for the first time channelling of light through nano-hole arrays filled with dispersive low-epsilon chalcogenides. The complex changes in the composite’s spectral response depend strongly on the interplay between the dispersion of the optical properties of the plasmonic nanostructure and the low-epsilon medium and lead to increase of transmission over a broad range of plasmonic frequencies.

• I have developed the first switchable UV metamaterials that exploits the low refractive index (equal to 1.07 at 245 nm for c-GST) and phase change properties of chalcogenides. In particular, I have shown that laser-induced structural phase transitions can be used to switch quality factors of dielectric resonances (QMax = 15) in metamaterials without affecting their spectral positions.

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Identifiers

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

ORCID for Kevin MacDonald: orcid.org/0000-0002-3877-2976

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