【作者】 刘丽；

【导师】 李洵； 张晨；

【作者基本信息】 山东大学 ， 电子科学与技术， 2025， 博士

【摘要】 在大数据与高速信息时代,高效、稳定的光子集成回路(PIC)成为光通信发展的关键。集成光学将体积光学中的概念缩小至微观尺度,使得各类光子器件能够集成到单个芯片上。在集成化进程中,磁光隔离器作为控制光单向传输的核心功能器件,扮演着不可替代的关键角色。目前,硅基磁光隔离器是光隔离器的主要方案,具有成本及损耗低等优势,但其尺寸、带宽等发展限制同样不可忽视。另外,目前主流的激光器、放大器等器件开发普遍采用Ⅲ-V族材料,其与硅基磁光隔离器的集成存在较大的纵向耦合损耗问题。基于绝缘体上GaAs平台的磁光隔离器具备与Ⅲ-Ⅴ族有源器件单片集成的天然优势,是新一代磁光隔离器的理想结构。但目前GaAs基磁光隔离器的单片集成和器件设计研究尚不充分,缺乏系统的理论分析和实践经验。针对该挑战,本文系统进行了 GaAs基磁光隔离器的理论推导和模场分布分析,揭示了影响其非互易相移(NRPS)的关键因素。分析了在绝缘体上GaAs平台集成磁光隔离器的结构与工艺可行性,随后,设计和优化了三种基于非对称马赫-曾德尔型(MZI)的GaAs基磁光隔离器,并对器件性能进行了对比和深入分析。主要研究工作和创新点如下:(1)不同非对角项下磁光波导中TM模式和TE模式的非互易性理论分析。基于磁光克尔效应角度从理论推导、数值仿真及模场分布三个维度阐释了 NRPS的物理机制及其影响因素,通过参数化非对角项条件计算了传播常数的特征方程,揭示了±χmn(±γ1β)耦合项是产生NRPS效应的直接原因,即:在不对称结构的基础上,磁化反转时,耦合项导致正反向传播常数的差异。同时,基于GaAs异质结构磁光波导的模场分布明确了影响NRPS值的关键因素:磁光包层电磁场的积分面积及场梯度。此外,适当调整核心层厚度与折射率可提升NRPS值。三维与二维、理论计算与仿真结果均呈现高度一致性。(2)基于绝缘体上GaAs的TM模式紧凑型磁光隔离器设计。TM模式的磁光隔离器是目前的主流方案,在微型化和高隔离度方面更具优势和应用潜力。为此,提出两种具有非对称MZI结构的TM模式磁光隔离器(结构A:针对晶圆键合工艺;结构B:针对激光脉冲沉积工艺),并基于器件参数对NRPS影响的系统性分析,实现了磁光波导和互易波导尺寸的最佳方案设计。通过有限元仿真分析,两种隔离器分别实现了大于53.5 nm和70 nm的35 dB隔离带宽,对应的插入损耗分别低至2.59 dB和2.25 dB。所设计磁光波导结构的最大NRPS值达到9000.39 rad/m,同时长度仅为174.53 μm,尺寸是现有结构的约25%,进一步提高器件的集成度。此外,设计了一种适用于上述两种结构的多模干涉(MMI)耦合器,来进一步提高器件性能与紧凑性。(3)基于绝缘体上AlGaAs的TE模式宽带型磁光隔离器设计。在半导体激光器普遍采用TE模式输出的需求驱动下,提出一种基于AlGaAs的宽带型磁光隔离器。通过优化侧壁沉积磁光材料的波导结构,实现了 2332.62rad/m的NRPS及673.40μm的磁光波导长度。通过三种耦合器的设计和对比分析,明确了引入锥形波导的MMI型耦合器具有最优性能,其插入损耗低至0.13 dB,是宽带高集成系统的首选。通过对整体器件的损耗优化,确定了在半径R=15 μm的弯曲波导尺寸下,器件的总损耗控制在1.47 dB。同时在30 dB隔离度下的带宽达到91 nm,是现有器件带宽的两倍以上,展现了其在宽带应用中的突出优势。(4)基于TE-TM模式转换的绝缘体上AlGaAs的TM模式高性能磁光隔离器设计。为兼容TM模式和TE模式隔离器的优点,即在保证宽带宽的同时,实现尺寸的微型化,提出单锥形波导(TE1-TMo)和双锥形波导(TE0-TMo)两种模式转换器结构。通过优化锥形波导参数和耦合区域,分别实现了高达99%和97%的模式转换效率。经优化后的磁光波导NRPS达到6100.597rad/m,长度仅为257.48μm,在26dB隔离度的带宽超过93 nm,总损耗控制在2.7 dB以内。分析表明,模式转换器引入的损耗相对较低,其中TE0-TM0的额外损耗仅为0.04 dB。同时器件的优值高达2.65 rad/dB,体现了器件良好的综合性能,这为实现兼具宽带宽和紧凑尺寸的磁光隔离器提供了有效的解决方案。综上,本文围绕绝缘体上GaAs平台的磁光隔离器展开系统的理论和结构设计分析,并针对不同的应用需求,提出三种具有不同性能优势的GaAs基磁光隔离器,包括:TM模式紧凑型磁光隔离器、TE模式宽带型磁光隔离器、具有TE-TM模式转换的高性能磁光隔离器。该器件及其设计方法在理论和工程应用层面均具有重要价值,可为下一代光通信系统中高集成度、宽带宽、低损耗的磁光隔离器提供了新的设计思路与技术路径。更多还原

【Abstract】 In the era of big data and high-speed information,efficient and stable photonic integrated circuit(PIC)have become a key factor in the development of optical communication.Integrated optics scales the concepts of volumetric optics down to the microscopic level,enabling various photonic devices to be integrated into a single chip.In this integration process,the magnetooptical isolator,as the core functional device for controlling unidirectional light transmission,plays an irreplaceable and critical role.Currently,silicon-based magneto-optical isolators are the main solution for optical isolation,offering advantages such as low cost and low loss.However,their limitations in terms of size,bandwidth,and other factors cannot be overlooked.Additionally,mainstream devices like lasers and amplifiers are typically developed using III-V materials,which pose significant vertical coupling loss challenges when integrated with siliconbased magneto-optical isolators.Magneto-optical isolators based on GaAs platforms on insulators have a natural advantage for monolithic integration with III-V active devices,making them an ideal structure for the next generation of magneto-optical isolators.However,the research on the monolithic integration and device design of GaAs-based magneto-optical isolators is still insufficient,lacking systematic theoretical analysis and practical experience.To address this challenge,this paper systematically derives the theory and analyzes the mode field distribution of GaAs-based magneto-optical isolators,revealing the key factors that influence their nonreciprocal phase shift(NRPS).The structural and process feasibility of integrating magneto-optical isolators on an insulator-based GaAs platform is also analyzed.Subsequently,three GaAs-based magneto-optical isolators based on asymmetric Mach-Zehnder interferometer(MZI)structures are designed and optimized,and the device performance is compared and deeply analyzed.The main research work and innovations are as follows:(1)Theoretical analysis of the nonreciprocity of TM and TE modes in magneto-optical waveguides under different off-diagonal terms.From the perspective of the magneto-optical Kerr effect,the physical mechanism of NRPS and its influencing factors are explained through theoretical derivation,numerical simulation,and mode field distribution.By parameterizing the off-diagonal terms,the characteristic equation of the propagation constant is calculated,revealing that the±χmn(±γ1β)coupling term is the direct cause of the NRPS effect.Specifically,based on the asymmetric structure,the coupling term causes a difference in the forward and backward propagation constants when the magnetization is reversed.At the same time,the mode field distribution of the GaAs heterostructure-based magneto-optical waveguide clearly identifies the key factors affecting the NRPS value:the integral area of the magneto-optical cladding electromagnetic field and the field gradient.Furthermore,adjusting the core layer thickness and refractive index appropriately can enhance the NRPS value.Both threedimensional and two-dimensional results,as well as theoretical and simulation results,show a high degree of consistency.(2)Design of a compact TM-mode magneto-optical isolator based on GaAs on insulator.TM-mode magneto-optical isolators are currently the mainstream solution,offering advantages and application potential in miniaturization and high isolation.To this end,two TM-mode magneto-optical isolators with asymmetric MZI structures are proposed:Structure A(for wafer bonding process)and Structure B(for laser pulse deposition process).Based on a systematic analysis of the impact of device parameters on NRPS,the optimal design for the sizes of the magneto-optical waveguide and reciprocal waveguide was achieved.Through finite element simulation,the two isolators achieved isolation bandwidths greater than 53.5 nm and 70 nm with 35 dB isolation,and corresponding insertion losses as low as 2.59 dB and 2.25 dB,respectively.The maximum NRPS value of the designed magneto-optical waveguide structure reached 9000.39 rad/m,while the length was only 174.53 μm,which is about 25%of the size of existing structures,further improving the device’s integration.Additionally,a multimode interference(MMI)coupler suitable for both structures was designed to further enhance the device’s performance and compactness.(3)Design of a broadband magneto-optical isolator based on AlGaAs for TE mode.Driven by the widespread demand for TE-mode output in semiconductor lasers,a broadband magnetooptical isolator based on AlGaAs is proposed.By optimizing the waveguide structure with magneto-optical material deposited on the sidewalls,an NRPS of 2332.62 rad/m and a magnetooptical waveguide length of 673.40 μm were achieved.Through the design and comparative analysis of three different couplers,it was determined that the MMI-type coupler with a tapered waveguide exhibits the best performance,with an insertion loss as low as 0.13 dB,making it the preferred choice for broadband,highly integrated systems,hrough optimization of the overall device loss,the total insertion loss was controlled at 1.47 dB under a bent waveguide radius of R=15μm.Meanwhile,the device achieved a bandwidth of 91 nm at 30 dB isolation,more than doubling the bandwidth of existing devices,demonstrating its outstanding advantages for broadband applications.(4)Design of a high-performance magneto-optical isolator based on TE-TM mode conversion on AlGaAs on insulator.To combine the advantages of both TM-mode and TE-mode isolators,specifically achieving miniaturization while ensuring a wide bandwidth,two mode converter structures are proposed:a single tapered waveguide(TE1-TM0)and a double tapered waveguide(TE0-TM0).By optimizing the parameters of the tapered waveguide and coupling region,mode conversion efficiencies of up to 99%and 97%were achieved,respectively.The optimized magneto-optical waveguide achieves an NRPS of 6100.597 rad/m with a length of only 257.48 μm,and the bandwidth at 26 dB isolation exceeds 93 nm,with total losses controlled to within 2.7 dB.Analysis shows that the loss introduced by the mode converter is relatively low,with the additional loss of the TE0-TM0 converter being only 0.04 dB.The device’s figure of merit reaches 2.65 rad/dB,demonstrating its excellent overall performance.This provides an effective solution for realizing magneto-optical isolators with both wide bandwidth and compact size.In summary,this paper presents a systematic theoretical and structural design analysis of magneto-optical isolators based on the GaAs on insulator platform.Three GaAs-basedd magneto-optical isolators with different performance advantages are proposed to meet various application needs:a compact TM-mode magneto-optical isolator,a broadband TE-mode magneto-optical isolator,and a high-performance magneto-optical isolator with TE-TM mode conversion.The device and its design methods are of significant value both in theory and engineering applications,offering new design ideas and technical paths for high integration,wide bandwidth,and low-loss magneto-optical isolators for next-generation optical communication systems.更多还原