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Widely tunable infrared semiconductor Mie resonators (Conference Presentation)
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Paper Abstract

Optical antenna metasurfaces have attracted substantial attention in recent years, as they may enable new classes of planar optical elements. However, actively tuning nanoantenna resonances, whether dielectric or plasmonic, remains an unresolved challenge. In this work, we investigate tuning mid-infrared (MIR) Mie resonances in semiconductor subwavelength particles by directly modulating the permittivity with free charge carriers. Using femtosecond laser ablation, we fabricate spherical silicon and germanium particles of varying sizes and doping concentrations. Single-particle infrared spectra reveal electric and magnetic dipole, quadrupole, and hexapole resonances. We first demonstrate size-dependent Si and Ge Mie resonances spanning the entire mid-infrared (2-16 μm) spectral range. We subsequently show doping-dependent resonance frequency shifts that follow simple Drude models. Taking advantage of the large doping dependence of Si and Ge MIR permittivities, we demonstrate a huge tunability of Mie resonance wavelengths (up to ~ 9 μm) over a broad 2-16 μm MIR range. This tuning range corresponds to changes of permittivity as large as 30 within a single material system, culminating in the emergence of plasmonic modes at high carrier densities and long wavelengths. We also demonstrate dynamic tuning of intrinsic semiconductor antennas using thermo-optic effects. These findings demonstrate the potential for actively tuning infrared Mie resonances, thus providing an excellent platform for tunable metamaterials.

Paper Details

Date Published: 9 November 2016
PDF: 1 pages
Proc. SPIE 9918, Metamaterials, Metadevices, and Metasystems 2016, 99180S (9 November 2016); doi: 10.1117/12.2237905
Show Author Affiliations
Tomer Lewi, Univ. of California, Santa Barbara (United States)
Prasad P. Iyer, Univ. of California, Santa Barbara (United States)
Nikita A. Butakov, Univ. of California, Santa Barbara (United States)
Alexander A. Mikhailovsky, Univ. of California, Santa Barbara (United States)
Jon A. Schuller, Univ. of California, Santa Barbara (United States)


Published in SPIE Proceedings Vol. 9918:
Metamaterials, Metadevices, and Metasystems 2016
Nader Engheta; Mikhail A. Noginov; Nikolay I. Zheludev, Editor(s)

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