Enhanced Q factor and robustness of photonic bound states in the continuum merging at locally bent trajectories

Bound states in the continuum (BICs) in planar photonic structures have attracted broad scientific interest owing to their exceptional capability to confine light. Topological robustness of certain BICs allows them to be moved in the momentum space by tuning the geometric parameters of the structure...

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Main Authors: Huayu Bai, Andriy Shevchenko, Radoslaw Kolkowski
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:JPhys Photonics
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Online Access:https://doi.org/10.1088/2515-7647/add1a1
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author Huayu Bai
Andriy Shevchenko
Radoslaw Kolkowski
author_facet Huayu Bai
Andriy Shevchenko
Radoslaw Kolkowski
author_sort Huayu Bai
collection DOAJ
description Bound states in the continuum (BICs) in planar photonic structures have attracted broad scientific interest owing to their exceptional capability to confine light. Topological robustness of certain BICs allows them to be moved in the momentum space by tuning the geometric parameters of the structure. In this work, we study such a BIC in a one-dimensional periodic grating, and find that its momentum-space position can be made a non-monotonic function of a geometric parameter, forming a locally bent V-shaped trajectory. We show that, near the turning point of this trajectory, the robustness of the BIC and its Q factor can be greatly enhanced. We tune such ‘V-BICs’ to almost merge with a symmetry-protected BIC at the Γ-point. This creates a K-shaped ultrahigh- Q region containing a BIC with a much higher and more stable Q factor compared to the ordinary merging BICs. The ‘K-BICs’ are also found to provide a strong enhancement of the Q factor in finite gratings over an extremely wide range of geometric parameters. Our findings enable further advancements in the development of ultrahigh- Q BICs and their applications.
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spelling doaj-art-2a85f9eb5c8c4288aaa0366cd679a93d2025-08-20T02:14:42ZengIOP PublishingJPhys Photonics2515-76472025-01-017303LT0110.1088/2515-7647/add1a1Enhanced Q factor and robustness of photonic bound states in the continuum merging at locally bent trajectoriesHuayu Bai0https://orcid.org/0000-0003-2046-9650Andriy Shevchenko1https://orcid.org/0000-0002-7621-2830Radoslaw Kolkowski2https://orcid.org/0000-0003-3866-9394Department of Applied Physics, Aalto University , PO Box 13500, Aalto FI-00076, FinlandDepartment of Applied Physics, Aalto University , PO Box 13500, Aalto FI-00076, FinlandDepartment of Applied Physics, Aalto University , PO Box 13500, Aalto FI-00076, FinlandBound states in the continuum (BICs) in planar photonic structures have attracted broad scientific interest owing to their exceptional capability to confine light. Topological robustness of certain BICs allows them to be moved in the momentum space by tuning the geometric parameters of the structure. In this work, we study such a BIC in a one-dimensional periodic grating, and find that its momentum-space position can be made a non-monotonic function of a geometric parameter, forming a locally bent V-shaped trajectory. We show that, near the turning point of this trajectory, the robustness of the BIC and its Q factor can be greatly enhanced. We tune such ‘V-BICs’ to almost merge with a symmetry-protected BIC at the Γ-point. This creates a K-shaped ultrahigh- Q region containing a BIC with a much higher and more stable Q factor compared to the ordinary merging BICs. The ‘K-BICs’ are also found to provide a strong enhancement of the Q factor in finite gratings over an extremely wide range of geometric parameters. Our findings enable further advancements in the development of ultrahigh- Q BICs and their applications.https://doi.org/10.1088/2515-7647/add1a1bound states in the continuumphotonic crystalstopological photonicsQ factor
spellingShingle Huayu Bai
Andriy Shevchenko
Radoslaw Kolkowski
Enhanced Q factor and robustness of photonic bound states in the continuum merging at locally bent trajectories
JPhys Photonics
bound states in the continuum
photonic crystals
topological photonics
Q factor
title Enhanced Q factor and robustness of photonic bound states in the continuum merging at locally bent trajectories
title_full Enhanced Q factor and robustness of photonic bound states in the continuum merging at locally bent trajectories
title_fullStr Enhanced Q factor and robustness of photonic bound states in the continuum merging at locally bent trajectories
title_full_unstemmed Enhanced Q factor and robustness of photonic bound states in the continuum merging at locally bent trajectories
title_short Enhanced Q factor and robustness of photonic bound states in the continuum merging at locally bent trajectories
title_sort enhanced q factor and robustness of photonic bound states in the continuum merging at locally bent trajectories
topic bound states in the continuum
photonic crystals
topological photonics
Q factor
url https://doi.org/10.1088/2515-7647/add1a1
work_keys_str_mv AT huayubai enhancedqfactorandrobustnessofphotonicboundstatesinthecontinuummergingatlocallybenttrajectories
AT andriyshevchenko enhancedqfactorandrobustnessofphotonicboundstatesinthecontinuummergingatlocallybenttrajectories
AT radoslawkolkowski enhancedqfactorandrobustnessofphotonicboundstatesinthecontinuummergingatlocallybenttrajectories