Bound states in the continuum on periodic structures surrounded by strong resonances

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal

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Original languageEnglish
Article number043828
Journal / PublicationPhysical Review A
Volume97
Issue number4
Online published13 Apr 2018
Publication statusPublished - Apr 2018

Abstract

Bound states in the continuum (BICs) are trapped or guided modes with their frequencies in the frequency intervals of the radiation modes. On periodic structures, a BIC is surrounded by a family of resonant modes with their quality factors approaching infinity. Typically the quality factors are proportional to 1/|β β|2, where β and β are the Bloch wave vectors of the resonant modes and the BIC, respectively. But for some special BICs, the quality factors are proportional to 1/|β β|4. In this paper, a general condition is derived for such special BICs on two-dimensional periodic structures. As a numerical example, we use the general condition to calculate special BICs, which are antisymmetric standing waves, on a periodic array of circular cylinders, and show their dependence on parameters. The special BICs are important for practical applications, because they produce resonances with large quality factors for a very large range of β.