Bound states in the continuum and Fano resonances in the strong mode coupling regime  

作　　者：Andrey A.Bogdanov Kirill LKoshelev Polina VKapitanova Mikhail VRybin Sergey AGladyshev Zarina FSadrieva Kirill BSamusev Yuri SKivshar a Mikhail FLimonov 

机构地区：[1]ITMO University,Department of Nanophotonics and Metamaterials,St.Petersburg,Russia [2]Ioffe Institute,St.Petersburg,Russia [3]Australian National University,Nonlinear Physics Center,Canberra,Australia

出　　处：《Advanced Photonics》2019年第1期33-44,共12页先进光子学（英文）

基　　金：We acknowledge fruitful discussions with H.Atwater,I.V.Shadrivov,P.A.Belov,A.N.Poddubny,A.Polman,and A.Moroz.The numerical calculations were performed with support from the Ministry of Education and Science of the Russian Federation(Project 3.1500.2017/4.6);the Australian Research Council.The experimental study of the cylinder SCS in the microwave frequency range was supported by the Russian Science Foundation(17-79-20379);The analytical calculations with resonant-state expansion method were performed with support from the Russian Science Foundation(17-12-01581)。

摘　　要：The study of resonant dielectric nanostructures with a high refractive index is a new research direction in the nanoscale optics and metamaterial-inspired nanophotonics.Because of the unique optically induced electric and magnetic Mie resonances,high-index nanoscale structures are expected to complement or even replace different plasmonic components in a range of potential applications.We study a strong coupling between modes of a single subwavelength high-index dielectric resonator and analyze the mode transformation and Fano resonances when the resonator’s aspect ratio varies.We demonstrate that strong mode coupling results in resonances with high-quality factors,which are related to the physics of bound states in the continuum when the radiative losses are almost suppressed due to the Friedrich–Wintgen scenario of destructive interference.We explain the physics of these states in terms of multipole decomposition,and show that their appearance is accompanied by a drastic change in the far-field radiation pattern.We reveal a fundamental link between the formation of the high-quality resonances and peculiarities of the Fano parameter in the scattering cross-section spectra.Our theoretical findings are confirmed by microwave experiments for the scattering of high-index cylindrical resonators with a tunable aspect ratio.The proposed mechanism of the strong mode coupling in single subwavelength high-index resonators accompanied by resonances with high-quality factors helps to extend substantially functionalities of all-dielectric nanophotonics,which opens horizons for active and passive nanoscale metadevices.

关 键 词：Fano resonance bound states in the continuum Mie resonance dielectric resonator meta-optics 

分 类 号：TB383.1[一般工业技术—材料科学与工程]