【作者】 张英杰；

【导师】 李俊庆；

【作者基本信息】 哈尔滨工业大学 ， 物理学， 2024， 博士

【摘要】 随着社会的发展,人们对于通信需求的快速增长导致通信系统的建设以及维护成本激增。为了增加通信效率以及降低通信成本,各类基于波导的复用技术被开发出来,包括时分复用、频分复用、空分复用以及模分复用等。其中,模分复用技术可以利用不同的模式作为数据传输的通道,极大地提升了信道数量。然而,常规波导中的“模式简并”可能会导致复用信道之间的频率干扰、码间干扰及功率分配不均等。因此,设计用以减少信道之间串扰的新型波导成为复用通信技术的未来发展趋势。相较于常规波导,手性波导中的“模式分裂”有利于增加信道数量以及减少信道之间的串扰。然而,当前手性波导结构中的模式特性研究还不够完善,尤其在手性表面等离激元模式、手性反谐振模式、手性连续域束缚态以及手性单向导模共振态的模式特性等方面。针对上述不足,本文主要研究波导结构中手性表面等离激元、手性反谐振模式、偶然型手性连续域束缚态以及手性单向导模共振态的模式特性,包括色散、损耗、场分布、能带结构、品质因子以及手性光学响应等。本研究对波导模式的理论体系的丰富、新一代滤波器的设计、波导通讯频段的拓宽、波导器件的集成化发展等具有重要的意义。本文的主要研究内容如下:首先,研究了介电手性材料与单层石墨烯构成的圆柱纳米线波导中表面等离激元模式的特性。手性参数导致具有混合偏振分布的同阶表面等离激元涡旋模式之间发生“模式分裂”,并且可以有效地增加模式的传输长度。此外,纳米线的半径以及石墨烯的费米能级可以调控模式的色散、传输长度以及模式的数量。该表面等离激元模式特性可应用于通信、手性分子检测和可调谐纳米光子器件等领域。其次,研究了介电手性材料构成的手性反谐振圆柱波导中反谐振模式的特性。手性参数导致位于管区的同阶手性反谐振模式之间发生“模式分裂”现象,相应地,同阶手性芯模和管模之间的耦合也会存在差异。基于这种耦合差异,实现了单圆偏振反谐振模式传输,并且手性参数的符号可以控制单圆偏振反谐振模式传输的偏振旋向。该工作在复用通信、手性传感和可调谐纳米光子器件的设计方面具有潜在的应用价值。再次,研究了一维光子晶体波导中偶然型手性连续域束缚态的模式特性。通过打破芯区结构的镜像对称,将结构手性引入到该光子晶体波导中,继而导致其所支持偶然型手性准连续域束缚态模式的向上以及向下辐射通道之间的远场偏振以及品质因子呈现反对称分布。利用平面波激励偶然型手性准连续域束缚态,通过偶然型手性准连续域束缚态的向下辐射通道实现了具有偏振转换功能的高品质因子单向手性光学响应。最后,研究了一维光子晶体波导中手性单向导模共振态的模式特性。通过同时打破芯区结构的镜像对称以及反转对称性,将手性引入到该光子晶体波导中,这导致手性单向导模共振态模式的向上与向下辐射通道之间在远场偏振分布、辐射损耗与品质因子等方面存在差异。同样利用平面波激励相应的模式,通过手性准单向导模共振态模式的向下辐射通道实现了具有偏振保持功能的高品质因子单向手性光学响应。更多还原

【Abstract】 With the development of society,the rapid growth of people’s demand for commu-nication has led to a surge in the construction and maintenance costs of communication systems.In order to increase the communication efficiency and reduce the communica-tion cost,various waveguide based multiplexing technologies have been developed,in-cluding time division multiplexing,frequency division multiplexing,space division mul-tiplexing and mode division multiplexing.Among them,mode division multiplexing can utilize different modes as transmission channels to increase the number of channels.How-ever,“mode degeneracy”in conventional waveguides may lead to frequency interference,inter-symbol inter-ference and uneven power distribution between multiplexed channels.Therefore,novel waveguides designed to reduce crosstalk between channels become the future development trend of multiplex communication technology.Compared with con-ventional waveguides,“mode bifurcation”in chiral waveguides is beneficial to increase the number of channels and reduce the crosstalk between channels.However,current re-search on the characteristics of modes in chiral waveguide structures is not sufficiently comprehensive,especially in the aspects of chiral surface plasmon mode,chiral anti-resonance mode,chiral bound states in the continuum(BIC)and chiral unidirectional guided resonance states.To address these shortcomings,this thesis investigates the char-acteristics of chiral surface plasmon mode,chiral anti-resonance mode,accidental chiral BIC,and chiral unidirectional guided resonance states in waveguide structures,including the dispersion,loss and field distribution,band structures,quality factors and chiroptical responses.The content of this thesis is significant for enriching the theoretical system of waveguide modes,designing the next generation of filters,broadening the communica-tion frequency band of waveguides,and promoting the integration and miniaturization of waveguide devices.The main research content of this thesis is as follows:Firstly,the characteristics of chiral surface plasmon mode in a cylindrical nanowire waveguide composed of dielectric chiral materials and mono-layer graphene are studied.Chiral parameter causes”mode bifurcation”between the same order surface plasmon vor-tex modes with hybrid polarization distribution,and can increase the propagation length of the modes.In addition,the radius of the nanowires and the Fermi level of the graphene can modulate the dispersion,the propagation length and the number of modes.The char-acteristics of chiral surface plasmon mode can be applied to multiplexed communication,chiral molecular detection and tunable nanophotonics devices.Secondly,the characteristics of chiral anti-resonance modes in chiral anti-resonance waveguides composed of dielectric chiral materials are examined.Chiral parameter causes”mode bifurcation”between the same order chiral antir-esonant modes in the tube region,correspondingly,the coupling between the same order chiral core and the tube modes is also different.Based on this coupling difference,the operation of single circular polariza-tion anti-resonance mode is realized,and the sign of the chiral parameter can control the rotation direction of polarization of anti-resonance mode.This work has potential appli-cation in multiplexed communication,chiral sensing and tunable nanophotonic devices.Thirdly,the characteristics of accidental chiral BIC modes in one-dimensional chiral photonic crystal waveguide structures are studied.By breaking the mirror-symmetry of the core structure,the structural chirality is introduced into the photonic crystal waveg-uide,and the far field polarization and quality factor between the upward and downward radiation channels of accidental chiral BIC modes present anti-symmetric distribution.The plane wave is used to excite accidental chiral BIC modes,and the downward radia-tion channel of the chiral quasi-accidental BIC modes can realize the high quality factor unidirectional chiroptical response with polarization conversion function.Finally,the characteristics of chiral unidirectional guided resonance states in one-dimensional chiral photonic crystal waveguide structures are investigated.By simultane-ously breaking the mirror-symmetry and reversion-symmetry of the core structure,struc-tural chirality is introduced into the photonic crystal waveguide,which causes the differ-ences in the far field polarization distribution,radiation loss and quality factor between the upward and downward radiation channels.By the downward radiation channel,the chiral quasi-unidirectional guided resonance states can support a high quality factor uni-directional chiroptical responses with maintaining polarization.更多还原