Bound States in the Continuum in a T-Shape Nanohole Array Perforated in a Photonic Crystal Slab
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Bound States in the Continuum in a T-Shape Nanohole Array Perforated in a Photonic Crystal Slab Suxia Xie 1,2,3
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Song Xie 1 & Jie Zhan 1 & Changzhong Xie 1 & Guang Tian 1 & Zhijian Li 1,3,4 & Qiong Liu 1
Received: 4 October 2019 / Accepted: 17 February 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract We have studied the reflectance spectra of T-shape nanohole array in a layer of Photonic crystal (PhC) slab. Results show that light can be confined perfectly in the PhC slab at a given incident angle at a suitable hole shape, hole size, layer thickness, and refractive index of surrounding medium. We obtained that the Q-factor at BIC can exceed 105, and the wavelength, incident angle of BIC can be modulated by structure parameters and surrounding mediums dielectric factor. Especially, the BIC has high sensitivity to the refractive index of the surrounding medium. The results can be helpful in the design of new-type photonics devices, such as filters and sensors. Keywords Photonic crystal . Nanohole array . Bound states in the continuum . Q-factor . Refractive index
Introduction The localization of waves is always more difficult to control than their propagation. Perfect optical constraints can be achieved as a result of a special type of local state: the bound state in the continuum (BIC) [1]. It has been proved that the direct interaction between the quasi-static state and the continuum interaction can produce BIC [2–4], ,which can be regarded as a resonance with infinite lifetime. Historically, von Neumann and Wigner [5] first proposed that when the wave function exhibits a weakly damped oscillation, BIC can be explicitly constructed in a quantum system and interpreted as a quasi-steady state, interference between the direct channel and the continuous medium channel [2]. It is
* Suxia Xie [email protected] * Jie Zhan [email protected] 1
School of Physics and Electronic Science, Hunan University of Science and Technology, Xiangtan, People’s Republic of China
2
School of Mechanical Engineering, University of Shanghai for Science and Technology, Shanghai, People’s Republic of China
3
Department of Electrical and Computer Engineering, University of Wisconsin, Madison, WI, USA
4
College of Electrical and Information Engineering, Hunan University, Changsha, People’s Republic of China
a very common effect and is important in many fields of physics, including photonics [6–9], quantum [10–14], hydraulics, and sound waves [15, 16]. The term BICs first appeared in the field of optics around 2008 [7, 9], although this phenomenon has been studied previously [17–20]. Experimental observations of optical BICs were only conducted in 2011 [6]. Recently, BIC has been demonstrated in photonic crystal (PhC) plates [21], where the periodic geometry results in a BIC at the Γ of the photonic band structure, which is similar to the electron band structure in solids [22–26]. This special resonant state has high quality characteristics, making it a promising application in many fields such as fi
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