Bound States in the Continuum in double layer structures

Li, Liangsheng; Yin, Hongcheng

doi:10.1038/srep26988

Cited by 50 publications

(43 citation statements)

References 28 publications

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“…From Eqs. (25) and (26) above, we obtain b − 1 = b + 1 = 0. Therefore, Im(ω 4 ) = 0 and u 2 does not radiate out power as x → ±∞.…”

Section: Structural Perturbationmentioning

confidence: 64%

Perturbation theories for symmetry-protected bound states in the continuum on two-dimensional periodic structures

Yuan

2020

Phys. Rev. A

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On dielectric periodic structures with a reflection symmetry in a periodic direction, there can be antisymmetric standing waves (ASWs) that are symmetry-protected bound states in the continuum (BICs). The BICs have found many applications, mainly because they give rise to resonant modes of extremely large quality-factors (Q-factors). The ASWs are robust to symmetric perturbations of the structure, but they become resonant modes if the perturbation is non-symmetric. The Q-factor of a resonant mode on a perturbed structure is typically O(1/δ 2 ) where δ is the amplitude of the perturbation, but special perturbations can produce resonant modes with larger Q-factors. For twodimensional (2D) periodic structures with a 1D periodicity, we derive conditions on the perturbation profile such that the Q-factors are O(1/δ 4 ) or O(1/δ 6 ). For the unperturbed structure, an ASW is surrounded by resonant modes with a nonzero Bloch wave vector. For 2D periodic structures, the Q-factors of nearby resonant modes are typically O(1/β 2 ), where β is the Bloch wavenumber. We show that the Q-factors can be O(1/β 6 ) if the ASW satisfies a simple condition.

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“…From Eqs. (25) and (26) above, we obtain b − 1 = b + 1 = 0. Therefore, Im(ω 4 ) = 0 and u 2 does not radiate out power as x → ±∞.…”

Section: Structural Perturbationmentioning

confidence: 64%

Perturbation theories for symmetry-protected bound states in the continuum on two-dimensional periodic structures

Yuan

2020

Phys. Rev. A

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“…Up to now, the existence of BICs and their location in the parameter space has been calculated either with rigorous numerical methods [26][27][28][29] , coupled-wave theory [30][31][32] , or a perturbation approach 13,33 . Some interesting proposals of numerical approaches especially suitable for such problems have been put forward 34,35 .…”

Section: Introductionmentioning

confidence: 99%

Bound states in the continuum in symmetric and asymmetric photonic crystal slabs

et al. 2020

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We develop a semi-analytical model to describe bound states in the continuum (BICs) in photonic crystal slabs. We model leaky modes supported by photonic crystal slabs as a transverse Fabry-Perot resonance composed of a few propagative Bloch waves bouncing back and forth vertically inside the slab. This multimode Fabry-Perot model accurately predicts the existence of BICs and their positions in the parameter space. We show that, regardless of the slab thickness, BICs cannot exist below a cut-off frequency, which is related to the existence of the second-order Bloch wave in the photonic crystal. Thanks to the semi-analyticity of the model, we investigate the dynamics of BICs with the slab thickness in symmetric and asymmetric photonic crystal slabs. We evidence that the symmetry-protected BICs that exist in symmetric structures at the Γ-point of the dispersion diagram can still exist when the horizontal mirror symmetry is broken, but only for particular values of the slab thickness.

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“…A particularly simple structure supporting BICs is a slab waveguide with anisotropic core and substrate [11,12]. Many recent works are concerned with BICs on periodic structures, including two-dimensional (2D) structures with one periodic direction [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], threedimensional (3D) biperiodic structures [28][29][30][31][32][33][34][35][36][37], and 3D rotationally symmetric structures [38,39]. In these studies, the periodic structures are sandwiched between or surrounded by homogeneous media, the BICs are guided Bloch modes above the lightline, and the radiative waves are propagating plane waves in the homogeneous media.…”

Section: Introductionmentioning

confidence: 99%

Bound states with complex frequencies near the continuum on lossy periodic structures

Zhen

Yuan

2020

Phys. Rev. A

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On a lossless periodic dielectric structure sandwiched between two homogeneous media, bound states in the continuum (BICs) with real frequencies and real Bloch wavevectors may exist, and they decay exponentially in the surrounding homogeneous media and do not couple with propagating plane waves with the same frequencies and wavevectors. The BICs are of significant current interest, because they give rise to high-Q resonances when the structure or the Bloch wavevector is slightly perturbed. In this paper, the effect of a small material loss on the BICs is analyzed by a perturbation method and illustrated by numerical results. It is shown that bound states with complex frequencies near the continuum appear, but they behave differently depending on whether the BIC is symmetryprotected or not. The Bloch wavevector of a bound state with a complex frequency can be real if the original BIC is symmetry-protected, and it is usually complex if the original BIC is not symmetryprotected. Our study improves the theoretical understanding on BICs and provides useful insight for their practical applications.

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Bound States in the Continuum in double layer structures

Cited by 50 publications

References 28 publications

Perturbation theories for symmetry-protected bound states in the continuum on two-dimensional periodic structures

Perturbation theories for symmetry-protected bound states in the continuum on two-dimensional periodic structures

Bound states in the continuum in symmetric and asymmetric photonic crystal slabs

Bound states with complex frequencies near the continuum on lossy periodic structures

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