Bound States in the Continuum in Fiber Bragg Gratings

Gao, Xingwei; Zhen, Bo; Soljačić, Marin; Chen, Hongsheng; Hsu, Chia Wei

doi:10.1021/acsphotonics.9b01202

Cited by 83 publications

(46 citation statements)

References 72 publications

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“…Here, we propose another system for the possible experimental realization of the found phenomena. The system considered is a photonic crystal fiber with periodic index modulations ( 38 ) shown in the inset of Fig. 5A , where the two components of the dielectric core are of equal thickness, i.e., d = 0.5 a , and have relative permittivities ε 1 = 4.9 and ε 2 = 1.…”

Section: Resultsmentioning

confidence: 99%

Coexistence of a new type of bound state in the continuum and a lasing threshold mode induced by PT symmetry

Song

Dai

et al. 2020

Sci. Adv.

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Some photonic systems support bound states in the continuum (BICs) that have infinite lifetimes, although their frequencies and momenta are matched to vacuum modes. Using a prototypical system that can be treated analytically, we show that each of these BICs always splits into a pair of new type BIC and lasing threshold mode when a parity-time (PT)–symmetric perturbation is introduced. The radiation loss at the lasing threshold is exactly balanced by the net gain of the particles. These PT symmetry-induced BICs are different from ordinary BICs, as they can be excited by an external source but do not radiate, and they carry a different quality factor divergence rate from that of the ordinary BICs. While most of the attention of PT-symmetric systems is captured by the coalescence of modes at exceptional points, the splitting of ordinary BICs is a new phenomenon that illustrates the rich physics embedded in PT-symmetric systems.

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Section: Resultsmentioning

confidence: 99%

Coexistence of a new type of bound state in the continuum and a lasing threshold mode induced by PT symmetry

Song

Dai

et al. 2020

Sci. Adv.

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“…Optical bound states in the continuum (BICs) are special electromagnetic states that remain well localized in photonic structures even though they coexist with outgoing waves that can carry electromagnetic energy away from the photonic structure [4][5][6][7][8]. Diverse types of BICs have been implemented in various photonic systems, including metasurfaces [9][10][11], photonic crystals [12][13][14][15][16][17], plasmonic structures [18], and fiber Bragg gratings [19]. Recently, robust BICs in subwavelength photonic crystal slab geometry have attracted much attention because they are associated with interesting topological physical phenomena [20][21][22][23] as well as practical applications, such as lasers [24,25], sensors [26,27], and filters [28].…”

Section: Introductionmentioning

confidence: 99%

Bound states in the continuum (BIC) accompanied by avoided crossings in leaky-mode photonic lattices

2020

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When two nonorthogonal resonances are coupled to the same radiation channel, avoided crossing arises and a bound state in the continuum (BIC) appears with appropriate conditions in parametric space. This paper presents numerical and analytical results on the properties of avoided crossing and BIC due to the coupled guided-mode resonances in one-dimensional (1D) leaky-mode photonic lattices with slab geometry. In symmetric photonic lattices with up-down mirror symmetry, Friedrich–Wintgen BICs with infinite lifetime are accompanied by avoided crossings due to the coupling between two guided modes with the same transverse parity. In asymmetric photonic lattices with broken up-down mirror symmetry, quasi-BICs with finite lifetime appear with avoided crossings because radiating waves from different modes cannot be completely eliminated. We also show that unidirectional-BICs are accompanied by avoided crossings due to guided-mode resonances with different transverse parities in asymmetric photonic lattices. The Q factor of a unidirectional-BIC is finite, but its radiation power in the upward or downward direction is significantly smaller than that in the opposite direction. Our results may be helpful in engineering BICs and avoided crossings in diverse photonic systems that support leaky modes.

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“…This is a precursor of the bound states in the continuum not caused by a symmetry mismatch. Such phenomena are predicted for DBR pillars by Bulgakov and Sadreev [24] and Gao et al [25].…”

Section: D Photonic Band Structurementioning

confidence: 55%

Hybrid method of plane-wave and cylindrical-wave expansions for distributed Bragg-reflector pillars: formalism and its application to topological photonics

Ochiai

2018

J. Opt. Soc. Am. B

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A hybrid computational method of plane-wave and cylindrical-wave expansions for distributed Bragg-reflector (DBR) pillars is proposed. The plane-wave expansion is employed to represent the one-dimensional periodic structure of the DBR. The cylindrical-wave expansion is employed to describe the scattering by circular pillars with the DBR structure inside. This formalism enables us to calculate the radiation fields, t-matrices, scattering cross sections, photonic band structures, and quality factors of the DBR pillars. Furthermore, optical properties of arrayed DBR pillars are also investigated with the aid of the multiple-scattering method. Using this formalism, we demonstrate explicitly that high Q photonic band modes including the so-called bound states in continuum are obtained both in isolated and arrayed DBR pillars. We also present a novel formation of gapless Dirac-cone surface states in a three-dimensional photonic crystal composed of a two-dimensional periodic arrangement of core-shell DBR pillars.

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Bound States in the Continuum in Fiber Bragg Gratings

Cited by 83 publications

References 72 publications

Coexistence of a new type of bound state in the continuum and a lasing threshold mode induced by PT symmetry

Coexistence of a new type of bound state in the continuum and a lasing threshold mode induced by PT symmetry

Bound states in the continuum (BIC) accompanied by avoided crossings in leaky-mode photonic lattices

Hybrid method of plane-wave and cylindrical-wave expansions for distributed Bragg-reflector pillars: formalism and its application to topological photonics

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