Multiple Epsilon-Near-Zero Resonances in Multilayered Cadmium Oxide: Designing Metamaterial-Like Optical Properties in Monolithic Materials

Kyle P. Kelley, Evan L. Runnerstrom, Edward Sachet, Christopher T. Shelton, Everett D. Grimley, Andrew Klump, James M. Lebeau, Zlatko Sitar, Jonathan Y. Suen, Willie J. Padilla, Jon Paul Maria

Research output: Contribution to journalArticlepeer-review

40 Scopus citations

Abstract

In this Letter, we demonstrate a new class of infrared nanophotonic materials based on monolithic, multilayered doped cadmium oxide (CdO) thin films, where each CdO layer is individually tuned to support a separate epsilon-near-zero (ENZ) resonance. Infrared reflectivity measurements reveal that the optical response of the multilayered stack combines multiple discrete absorption events, each associated with an individual ENZ plasmonic polaritonic mode. Structural and chemical characterization confirm that the multilayers are homoepitaxial and monolithic, with internal interfaces defined by discrete steps in dopant density and carrier concentration. Structurally, the layers are indistinguishable as they differ from their neighbors by only â1 in 10000 constituent atoms. The optoelectronic property contrast, however, is pronounced, as each layer maintains an independent electron concentration, as corroborated by secondary ion mass spectroscopy and numerical solutions to Poisson's equation. It is this electron confinement that imbues each individual layer with the ability to independently resonate at separate mid-infrared frequencies. We additionally demonstrate simultaneous thermal emission of infrared light from each individual layer at its respective ENZ frequency, pursuant to Kirchhoff's law of radiation. The highly localized property contrast intrinsic to these monoliths offers great potential in nanophotonics, plasmonics, and physics thanks to the ability to engineer infrared response and achieve metamaterial-like optical properties without the need for lithography or micro/nanofabrication. New possibilities arising from this work include strongly tunable and multimodal perfect absorbers as well as spectrally engineered and narrow-band light emitters.

Original languageEnglish
Pages (from-to)1139-1145
Number of pages7
JournalACS Photonics
Volume6
Issue number5
DOIs
StatePublished - May 15 2019
Externally publishedYes

Funding

We gratefully acknowledge support for this work by NSF Grant CHE-1507947, by Army Research Office Grants W911NF16-1-0406 and W911NF-16-1-0037, and by Office of Naval Research Grant N00014-18-12107. We also thank the Efimenko and Genzer groups (NCSU, CBE) for providing access to the IR-VASE. EDG and JML gratefully acknowledge support from the National Science Foundation (DMR-1350273). EDG acknowledges support for this work through a National Science Foundation Graduate Research Fellowship (DGE-1252376). The SIMS and STEM work was performed in part at the Analytical Instrumentation Facility (AIF), which is supported by the State of North Carolina and the National Science Foundation (Award Number ECCS-1542015). The AIF is a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), a site in the National Nanotechnology Coordinated Infrastructure (NNCI).

FundersFunder number
National Science FoundationDGE-1252376, ECCS-1542015, CHE-1507947, DMR-1350273
National Science Foundation
Office of Naval ResearchN00014-18-12107
Office of Naval Research
Army Research OfficeW911NF-16-1-0037, W911NF16-1-0406
Army Research Office

    Keywords

    • CdO
    • epsilon-near-zero
    • infrared
    • nanophotonics
    • plasmonics
    • thin film

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