Unveiling the Symmetry Protection of Bound States in the Continuum with Terahertz Near-Field Imaging

Niels J.J. van Hoof; Diego R. Abujetas; Stan E.T. ter Huurne; Francesco Verdelli; Giel C.A. Timmermans; José A. Sánchez-Gil; Jaime Gómez Rivas

doi:10.1021/acsphotonics.1c00937

Unveiling the Symmetry Protection of Bound States in the Continuum with Terahertz Near-Field Imaging

Niels J.J. van Hoof, Diego R. Abujetas, Stan E.T. ter Huurne, Francesco Verdelli, Giel C.A. Timmermans, José A. Sánchez-Gil, Jaime Gómez Rivas (Corresponding author)

Research output: Contribution to journal › Article › Academic › peer-review

44 Citations (Scopus)

Abstract

Bound states in the continuum (BICs) represent a new paradigm in photonics due to the full suppression of radiation losses. However, this suppression has also hampered the direct observation of them. By using a double terahertz (THz) near-field technique that allows the local excitation and detection of the THz amplitude, we are able to map for the first time the electromagnetic field amplitude and phase of BICs over extended areas, unveiling the field-symmetry protection that suppresses the far-field radiation. This investigation, done for metasurfaces of dimer scatterers, reveals the in-plane extension and formation of BICs with antisymmetric phases, in agreement with coupled-dipole calculations. By displacing the scatterers, we show experimentally that a mirror symmetry is not a necessary condition for a BIC formation. Only π-rotation symmetry is required, making BICs exceptionally robust to structural changes. This work makes the local field of BICs experimentally accessible, which is crucial for the engineering of cavities with infinite lifetimes.

Original language	English
Pages (from-to)	3010-3016
Number of pages	7
Journal	ACS Photonics
Volume	8
Issue number	10
DOIs	https://doi.org/10.1021/acsphotonics.1c00937
Publication status	Published - 20 Oct 2021

Funding

The authors thank K. de Mare for help in the development of the setup and Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) (Vici 680-47-628); Spanish Ministerio de Ciencia e Innovación (MICIU/AEI/FEDER, UE) through the grants MELODIA (PGC2018-095777–B-C21) and NANOTOPO (FIS2017-91413-EXP), and Ministerio de Educación, Cultura y Deporte through a PhD Fellowship (FPU15/03566) for funding.

Keywords

coupled dipole model
metasurfaces
Symmetry-protected bound states in the continuum
THz near-field microscopy
THz time-domain spectroscopy

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10.1021/acsphotonics.1c00937

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title = "Unveiling the Symmetry Protection of Bound States in the Continuum with Terahertz Near-Field Imaging",

abstract = "Bound states in the continuum (BICs) represent a new paradigm in photonics due to the full suppression of radiation losses. However, this suppression has also hampered the direct observation of them. By using a double terahertz (THz) near-field technique that allows the local excitation and detection of the THz amplitude, we are able to map for the first time the electromagnetic field amplitude and phase of BICs over extended areas, unveiling the field-symmetry protection that suppresses the far-field radiation. This investigation, done for metasurfaces of dimer scatterers, reveals the in-plane extension and formation of BICs with antisymmetric phases, in agreement with coupled-dipole calculations. By displacing the scatterers, we show experimentally that a mirror symmetry is not a necessary condition for a BIC formation. Only π-rotation symmetry is required, making BICs exceptionally robust to structural changes. This work makes the local field of BICs experimentally accessible, which is crucial for the engineering of cavities with infinite lifetimes. ",

keywords = "coupled dipole model, metasurfaces, Symmetry-protected bound states in the continuum, THz near-field microscopy, THz time-domain spectroscopy",

author = "{van Hoof}, {Niels J.J.} and Abujetas, {Diego R.} and {ter Huurne}, {Stan E.T.} and Francesco Verdelli and Timmermans, {Giel C.A.} and S{\'a}nchez-Gil, {Jos{\'e} A.} and {G{\'o}mez Rivas}, Jaime",

note = "Funding Information: The authors thank K. de Mare for help in the development of the setup and Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) (Vici 680-47-628); Spanish Ministerio de Ciencia e Innovaci{\'o}n (MICIU/AEI/FEDER, UE) through the grants MELODIA (PGC2018-095777–B-C21) and NANOTOPO (FIS2017-91413-EXP), and Ministerio de Educaci{\'o}n, Cultura y Deporte through a PhD Fellowship (FPU15/03566) for funding. Publisher Copyright: {\textcopyright} 2021 The Authors. Published by American Chemical Society.",

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AU - Verdelli, Francesco

AU - Timmermans, Giel C.A.

AU - Sánchez-Gil, José A.

AU - Gómez Rivas, Jaime

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PY - 2021/10/20

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N2 - Bound states in the continuum (BICs) represent a new paradigm in photonics due to the full suppression of radiation losses. However, this suppression has also hampered the direct observation of them. By using a double terahertz (THz) near-field technique that allows the local excitation and detection of the THz amplitude, we are able to map for the first time the electromagnetic field amplitude and phase of BICs over extended areas, unveiling the field-symmetry protection that suppresses the far-field radiation. This investigation, done for metasurfaces of dimer scatterers, reveals the in-plane extension and formation of BICs with antisymmetric phases, in agreement with coupled-dipole calculations. By displacing the scatterers, we show experimentally that a mirror symmetry is not a necessary condition for a BIC formation. Only π-rotation symmetry is required, making BICs exceptionally robust to structural changes. This work makes the local field of BICs experimentally accessible, which is crucial for the engineering of cavities with infinite lifetimes.

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Unveiling the Symmetry Protection of Bound States in the Continuum with Terahertz Near-Field Imaging

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