Extended bound states in the continuum with symmetry-broken terahertz dielectric metasurfaces

Excitation of the non-radiative eigenmodes in photonics and metamaterials above their light cone, that is, the bound states in the continuum (BICs), has drawn fundamental and technological interest. However, the current studies on photonic BICs are mainly restricted to the characterization of the ei...

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Main Authors: Han, Song, Pitchappa, Prakash, Wang, Wenhao, Srivastava, Yogesh Kumar, Rybin, Mikhail V., Singh, Ranjan
Other Authors: School of Physical and Mathematical Sciences
Format: Article
Language:English
Published: 2022
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Online Access:https://hdl.handle.net/10356/159928
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-1599282022-07-06T01:20:04Z Extended bound states in the continuum with symmetry-broken terahertz dielectric metasurfaces Han, Song Pitchappa, Prakash Wang, Wenhao Srivastava, Yogesh Kumar Rybin, Mikhail V. Singh, Ranjan School of Physical and Mathematical Sciences Institute of Microelectronics, A*STAR Centre for Disruptive Photonic Technologies (CDPT) The Photonics Institute Science::Physics Terahertz Symmetry-Broken Metasurfaces Topological Charges Excitation of the non-radiative eigenmodes in photonics and metamaterials above their light cone, that is, the bound states in the continuum (BICs), has drawn fundamental and technological interest. However, the current studies on photonic BICs are mainly restricted to the characterization of the eigenmodes with fixed point group. Here, a fourfold rotationally symmetric (C4v) array of silicon resonators in a square lattice is investigated that reveals the traditional symmetry-protected (Γ-state) and accidental (off-Γ) BICs in the momentum space. Upon symmetry-breaking, BICs at Γ-state transform into quasi-states with decaying quality factors that obey the inverse-square law α−2 as a function of the structural asymmetry parameter α. Surprisingly, at larger asymmetries, multiple new states of extended BICs are observed beyond typical inverse-square law behavior. The structural asymmetry of a resonator provides an important degree of freedom for exploring the Friedrich–Wintgen and new accidental BICs that are topologically protected by robust polarization vortices. The extended family of sharp BIC resonances in all-dielectric silicon metasurfaces is extremely important for scalable applications in terahertz sensing, higher harmonic generation, and ultralow-power switching. Ministry of Education (MOE) The authors acknowledge the financial support from the Singapore Ministry of Education (MOE) Academic Research Fund (AcRF) Tier 1 grant RG96/19, Tier 2 grant MOE2017-T2-1-110, and Tier 3 grant MOE2016-T3-1-006. 2022-07-06T01:20:04Z 2022-07-06T01:20:04Z 2021 Journal Article Han, S., Pitchappa, P., Wang, W., Srivastava, Y. K., Rybin, M. V. & Singh, R. (2021). Extended bound states in the continuum with symmetry-broken terahertz dielectric metasurfaces. Advanced Optical Materials, 9(7), 2002001-. https://dx.doi.org/10.1002/adom.202002001 2195-1071 https://hdl.handle.net/10356/159928 10.1002/adom.202002001 2-s2.0-85100152206 7 9 2002001 en RG96/19 MOE2017-T2-1-110 MOE2016-T3-1-006 Advanced Optical Materials © 2021 Wiley-VCH GmbH. All rights reserved.
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Science::Physics
Terahertz Symmetry-Broken Metasurfaces
Topological Charges
spellingShingle Science::Physics
Terahertz Symmetry-Broken Metasurfaces
Topological Charges
Han, Song
Pitchappa, Prakash
Wang, Wenhao
Srivastava, Yogesh Kumar
Rybin, Mikhail V.
Singh, Ranjan
Extended bound states in the continuum with symmetry-broken terahertz dielectric metasurfaces
description Excitation of the non-radiative eigenmodes in photonics and metamaterials above their light cone, that is, the bound states in the continuum (BICs), has drawn fundamental and technological interest. However, the current studies on photonic BICs are mainly restricted to the characterization of the eigenmodes with fixed point group. Here, a fourfold rotationally symmetric (C4v) array of silicon resonators in a square lattice is investigated that reveals the traditional symmetry-protected (Γ-state) and accidental (off-Γ) BICs in the momentum space. Upon symmetry-breaking, BICs at Γ-state transform into quasi-states with decaying quality factors that obey the inverse-square law α−2 as a function of the structural asymmetry parameter α. Surprisingly, at larger asymmetries, multiple new states of extended BICs are observed beyond typical inverse-square law behavior. The structural asymmetry of a resonator provides an important degree of freedom for exploring the Friedrich–Wintgen and new accidental BICs that are topologically protected by robust polarization vortices. The extended family of sharp BIC resonances in all-dielectric silicon metasurfaces is extremely important for scalable applications in terahertz sensing, higher harmonic generation, and ultralow-power switching.
author2 School of Physical and Mathematical Sciences
author_facet School of Physical and Mathematical Sciences
Han, Song
Pitchappa, Prakash
Wang, Wenhao
Srivastava, Yogesh Kumar
Rybin, Mikhail V.
Singh, Ranjan
format Article
author Han, Song
Pitchappa, Prakash
Wang, Wenhao
Srivastava, Yogesh Kumar
Rybin, Mikhail V.
Singh, Ranjan
author_sort Han, Song
title Extended bound states in the continuum with symmetry-broken terahertz dielectric metasurfaces
title_short Extended bound states in the continuum with symmetry-broken terahertz dielectric metasurfaces
title_full Extended bound states in the continuum with symmetry-broken terahertz dielectric metasurfaces
title_fullStr Extended bound states in the continuum with symmetry-broken terahertz dielectric metasurfaces
title_full_unstemmed Extended bound states in the continuum with symmetry-broken terahertz dielectric metasurfaces
title_sort extended bound states in the continuum with symmetry-broken terahertz dielectric metasurfaces
publishDate 2022
url https://hdl.handle.net/10356/159928
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