Journal
ACS PHOTONICS
Volume 7, Issue 2, Pages 416-424Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsphotonics.9b01368
Keywords
plasmonics; aluminum; nanoantenna; surface lattice resonances; inverse design; space mapping
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Funding
- National Science Foundation [ECCS-1611290]
- National Science Foundation CAREER Award [ECCS-1847733]
- National Institutes of Health (NIH) [5R21AI139790-0]
- University of California Chancellor's Dissertation Year Fellowship
- Army Research Office [W911NF-17-1-0460]
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Aluminum, with its distinctively favorable dielectric characteristics down to deep ultraviolet (UV) regime, has recently emerged as a broad-band and low-cost alternative to noble metals. However, low Q-factor resonances (Q similar to 2-4), offered by Al nanostructures, pose a fundamental bottleneck for many practical applications. Here, we show that it is possible to realize Al-nanoantenna with remarkably large extinction cross sections and strong resonance characteristics surpassing those of their noble metal counterparts. By quenching radiation damping through far-field coherent dipolar interactions, we experimentally demonstrate exceptionally narrow line width (similar to 15 nm) and high Q-factor (similar to 27) dipolar plasmonic resonances in the blue-violet region of the optical spectrum (similar to 3 eV) beyond the practical operational limits of traditional plasmonic metals. To realize high Q-factor Al resonators, we introduce a novel space mapping algorithm enabling inverse design of Al nanoantenna arrays at arbitrary sub/superstrate material interfaces with diminished radiative losses. We show that radiatively coupled Al nanoantenna arrays offer remarkably high-Q factor (27 <= Q <= 53) resonances over the entire visible spectrum and readily outperform similarly optimized silver (Ag) nanoantenna arrays in green-blue-violet wavelengths (<= 550 nm) and near UV regime. This report shows that it is possible to realize high Q-factor aluminum resonators by suppressing radiative losses and that Al-based plasmonics holds enormous potential as a viable and low-cost alternative to noble metals. Our inverse-design technique, on the other hand, provides a general and efficient approach in engineering of high Q-factor resonator arrays, independently from the metals and sub/superstrates used.
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