摘要
设计了一种由交替堆叠的二氧化硅和二氧化钛薄膜组成的新型多层膜光栅混合结构,该结构可以同时支持类导模共振和类布洛赫表面波模式。通过在周期性多层膜结构中引入缺陷层和改变多层膜禁带中心波长的方法,可以改变类导模共振和类布洛赫表面波模式之间的耦合程度,当两种模式的相位匹配时,两种模式发生干涉相消,形成共振耦合型BIC,品质因子高达10^(5)。通过改变光栅周期和光栅材料可以有规律地调控多层膜光栅混合结构所形成BIC的波长,为利用多层膜光栅结构设计高Q谐振器提供理论指导。
Objective In modern photonics and optics,the development of high-performance optical devices,such as sensors,lasers,and filters with ultra-high quality factor(Q-factor),is crucial.Bound states in the continuum(BICs)are considered an effective approach for achieving this goal,as they can theoretically reach an infinite Q-factor under ideal conditions,showing great potential for various applications.BICs are generally classified into two types based on their decoupling from far-field radiation:symmetry-protected BICs(S-P BICs)and resonance-coupled BICs,also known as parameter-tuned BICs.While S-P BICs are appealing due to their straightforward predictability,their practical realization often encounters significant obstacles,including intricate structural designs,limited integration capabilities,and complex design challenges.Resonance-coupled BICs,with their simpler structure and ease of fabrication,have become the focus of research.However,the Q-factor and structural integration of resonance-coupled BICs reported in the literature still require improvement.To address this challenge,we propose a novel multilayer grating hybrid structure composed of alternating silica and titanium dioxide films.By precisely controlling the bandgap center wavelength,grating period,and material parameters of the multilayer structure,the localization of the optical field is further enhanced,resulting in a significant increase in the Q-factor.This enhancement aims to achieve breakthroughs in optical device performance and open up new possibilities for advanced photonic applications.Methods Based on temporal coupled mode theory,a new structure for forming resonance-coupled BICs has been proposed.Using the reflection principle of the distributed Bragg reflector(DBR)method,a multilayer film structure is designed to precisely control the propagation and reflection characteristics of light waves within the multilayers.Utilizing equivalent medium theory in the design of grating structures can effectively regulate the propagation path of light waves,achieving precise control over their propagation characteristics.Finally,by employing the control variable method,we adjust system parameters such as the incident light angle,grating period,and grating material in a five-layer film grating structure to investigate the principles governing the realization of BIC in the hybrid multilayer film grating structure.Results and Discussions A novel multilayer grating hybrid structure composed of alternating silica and titanium dioxide films is designed by combining multilayer and grating structures(Fig.1).First,a thorough analysis of the potential modes in the structure is conducted.By comparing a simple TiO2 grating with the proposed multilayer grating structure,guidedmode resonance(like-GMR)and Bloch surface wave(like-BSW)modes are identified.The introduction of a defect layer allows the two modes to satisfy phase-matching conditions,leading to destructive interference between the modes and forming a resonance-coupled BIC,significantly enhancing field localization.By carefully designing the period and central wavelength of the multilayer structure,further refinements are made to precisely control the spatial distribution and coupling strength between the modes.This optimization achieves a high Q-factor of~105.In addition,the effects of incident light angle,grating period(P),and the refractive index of the grating material on the position and Q-factor of the resonant BIC are systematically studied,establishing a regular tuning strategy for achieving the resonant BIC.The results show that the incident angle has little influence on the BIC.As the grating period is incrementally enlarged,the wavelength at the BIC is observed to increase linearly,exhibiting a direct proportionality of about 1.5 times the period length.Although the material’s refractive index has a subtle effect on the BIC’s position,an increase in the refractive index is found to enhance field localization and achieve a high Q-factor(Fig.5).Conclusions In this paper,we propose a multilayer grating hybrid structure that effectively forms a resonance-coupled BIC.The results show that two optical modes,like-GMR and like-BSW,coexist in the hybrid structure.By adjusting the layer thickness,the resonant frequencies of the modes can be altered,leading to strong coupling between the two modes,reducing the resonant wavelength,and enhancing light localization.Introducing a defect layer of specific thickness on the surface of the multilayer system or altering the center wavelength of the multilayer bandgap structure can achieve phase matching between the two optical modes,forming a resonance-coupled BIC with a Q-factor up to 105.In the multilayer grating structure,the wavelength of the resonance-coupled BIC increases linearly with the grating period while maintaining a high Q-factor.Furthermore,enhancing the refractive index of the multilayer materials can improve the Q-factor of the resonance-coupled BIC,further intensifying the localization of field energy.This approach provides effective theoretical guidance for designing high-Q resonances across different wavelength bands.
作者
赵敏丞
许蓉蓉
邓玲玲
卜华银
宋雨辰
郑加金
Zhao Mincheng;Xu Rongrong;Deng Lingling;Bu Huayin;Song Yuchen;Zheng Jiajin(College of Electronic and Optical Engineering&College of Flexible Electronics(Future Technology),Nanjing University of Posts and Telecommunications,Nanjing 210023,Jiangsu,China)
出处
《光学学报》
北大核心
2025年第2期291-298,共8页
Acta Optica Sinica
基金
国家自然科学基金(11974188)
中国博士后科学基金(2021T140339,2018M632345)
江苏省博士后科学基金(2021K617C)。
关键词
导模共振
多层膜禁带特性
共振耦合型连续域束缚态
品质因子
guided-mode resonance
multilayer film forbidden band characteristics
resonance-coupled bound states in the continuum
quality factor
