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High-Q nanophotonics over the full visible spectrum enabled by hexagonal boron Nitride metasurfaces
Publikationstyp
Journal Article
Date Issued
2022-12-31
Sprache
English
Author(s)
Kühner, Lucca
Tilmann, Benjamin
Watanabe, Kenji
Taniguchi, Takashi
Journal
Volume
35
Issue
13
Article Number
2209688
Citation
Advanced Materials 35 (13): 2209688 (2022)
Publisher DOI
Scopus ID
Publisher
Wiley-VCH
All-dielectric optical metasurfaces with high quality (Q) factors have been hampered by the lack of simultaneously lossless and high-refractive-index materials over the full visible spectrum. In fact, the use of low-refractive-index materials is unavoidable for extending the spectral coverage due to the inverse correlation between the bandgap energy (and therefore the optical losses) and the refractive index (n). However, for Mie resonant photonics, smaller refractive indices are associated with reduced Q factors and low mode volume confinement. Here, symmetry-broken quasi bound states in the continuum (qBICs) are leveraged to efficiently suppress radiation losses from the low-index (n ≈ 2) van der Waals material hexagonal boron nitride (hBN), realizing metasurfaces with high-Q resonances over the complete visible spectrum. The rational use of low- and high-refractive-index materials as resonator components is analyzed and the insights are harnessed to experimentally demonstrate sharp qBIC resonances with Q factors above 300, spanning wavelengths between 400 and 1000 nm from a single hBN flake. Moreover, the enhanced electric near fields are utilized to demonstrate second-harmonic generation with enhancement factors above 10². These results provide a theoretical and experimental framework for the implementation of low-refractive-index materials as photonic media for metaoptics.
Subjects
bound states in the continuum
hexagonal boron nitride
high-Q resonances
low index photonics
DDC Class
600: Technology