【作者】 王玉；

【导师】 王春晖；

【作者基本信息】 哈尔滨工业大学 ， 电子科学与技术， 2025， 博士

【摘要】 激光雷达(Light Detection and Ranging,LiDAR)是一种通过发射激光束并分析反射信号来探测物体距离、形状和表面特征的主动探测技术,一般由激光发射器、接收器、扫描部件和数据处理单元构成,依据扫描方式可以分成机械式激光雷达和固态激光雷达。近年来,随着光子集成电路技术的突破,激光雷达正逐步从机械扫描架构向全固态集成化方向发展。基于焦平面开关阵列(Focal Plane Switch Array,FPSA)的芯片级光子集成激光雷达发射系统,凭借片上开关网络与片外透镜的结合,可以实现二维光束扫描。该系统兼具扫描视场角较大、可扩展性强及调制方式简单的优势,成为全固态激光雷达的下一代核心技术方案。然而,该技术目前仍面临一些技术挑战,包括大视场角与高精度角分辨率难以兼容、工艺水平制约下的阵列规模受限,以及系统发射功率难以满足探测距离需求等挑战。为了解决以上问题,本研究以光子激光雷达FPSA发射芯片为研究核心,以扩展发射阵列规模、降低系统复杂度、提升探测距离和增强整体光学效率为主要研究目标,系统性地研究了FPSA的整体架构及各光子集成器件,并通过实验进行了相关验证,主要研究内容如下:(1)光子激光雷达FPSA扫描原理与架构。基于FPSA的扫描原理,深入研究了光学天线、光开关网络和波分复用器的整体布局,提出了两种发射系统架构:大规模行扫描硅基FPSA发射系统架构和大规模高功率行扫描氮化硅基FPSA发射系统架构。硅基架构通过光开关网络控制光路,在列方向上自动寻址到特定的波导总线,从而实现光束在列方向的偏转控制。个由功率分配器和光栅耦合器组成的光学天线在行方向上同步发射,并结合片外透镜实现行方向的光束偏转控制。由此方法,系统可以通过少量的光开关网络实现大规模的二维光束扫描效果。氮化硅基架构则采用全氮化硅无源器件构建,无需光开关网络。该架构通过调制入射光的波长来实现在列方向的光束偏转控制,行方向的光束偏转控制仍由功率分配器、光栅耦合器和片外透镜的结合共同实现。(2)大规模低复杂度行扫描硅基FPSA发射系统研究。针对硅基FPSA发射架构的需求对其系统及各光子器件进行了优化设计。首先,利用遗传算法设计并优化了光栅耦合器的光栅区域、利用拓扑算法和片上超透镜理论设计了一种新型模式转换器,将两者结合实现了一种紧凑型光栅耦合器的设计。然后,针对马赫-曾德尔干涉仪光开关单元,基于多模干涉理论构建了基础模型,采用遗传算法和拓扑优化算法分别优化了多模干涉仪区域输入/输出端和弯曲连接波导,确保了最终设计的光开关具备较高的传输效率和较低的相位误差。其次,基于传统定向耦合器,利用拓扑优化算法设计不同功分比的功率分配器,以确保能将相同能量的光输出至发射光栅耦合器中。最后,在设计发射光栅耦合器时,综合考虑了耦合效率和模场匹配,进一步优化了发射模式的光束质量。(3)大规模高功率行扫描氮化硅基FPSA发射系统研究。针对氮化硅基FPSA发射架构的需求对各光子器件进行了相关设计和优化,首先,基于模场匹配原理,设计了倒锥形边缘耦合器和小尺寸多级三叉型边缘耦合器,在宽波长范围内大幅提高了耦合效率。然后,针对波分复用器,设计了大规模阵列波导光栅和小尺寸验证的阵列波导光栅,并优化了阵列波导及弯曲波导。为适应更大规模的发射阵列,提出了阵列波导光栅与多模干涉仪波分器级联的设计方案,并利用拓扑优化算法优化了宽波长多模干涉仪波分器,提高了耦合效率和波长适应性。其次,结合深度学习算法与遗传算法,成功完成了不同波长下发射光栅耦合器的快速设计,显著提高了设计效率。最后,基于超透镜仿真设计了一种新型片外透镜,能几乎无像差地实现对光栅耦合器辐射光的角度偏转控制。(4)光子激光雷达FPSA发射芯片测试与分析。采用紫外光刻与电子束光刻技术制备了两种光子激光雷达FPSA发射芯片,并结合光波导耦合平台搭建了发射芯片远场测试系统。根据实际加工规模,设计并仿真了片外透镜,结合高精度电压源完成了远场光束扫描测试。通过对视场、角分辨率、发散角和光束消光比等参数的分析,评估了整体性能,验证了所提出的两种架构在实际应用中的有效性。更多还原

【Abstract】 LiDAR(Light Detection and Ranging)is an active sensing technology that detects the distance,shape,and surface characteristics of objects by transmitting laser beams and analyzing the reflected signals.A typical LiDAR system consists of a laser transmitter,receiver,scanning module,and data processing unit.Based on the scanning method,LiDAR systems can be categorized into mechanical and solid-state types.In recent years,with advancements in photonic integrated circuit technology,LiDAR is gradually transitioning from mechanical scanning architectures to all-solid-state integration.Specifically,the chip-level photonic integrated LiDAR transmitter system based on the Focal Plane Switch Array(FPSA)can achieve two-dimensional beam scanning through the integration of on-chip switching networks and off-chip lens.This system offers advantages such as a large scanning field of view,strong scalability,and simple modulation methods,making it the next-generation core technology solution for all-solid-state LiDAR.However,the technology still faces several challenges,including difficulties in achieving compatibility between wide field of view and high angular resolution,limitations on the array scale due to fabrication constraints,and the inability of the system’s transmission power to meet the detection range requirements.To address the aforementioned challenges,this work focuses on the photonic LiDAR FPSA transmitter chip,with primary research objectives of expanding the transmitting array scale,reducing chip complexity,increasing detection range,and enhancing overall optical efficiency.It systematically investigates the FPSA architecture and individual photonic integrated devices,validated through experimental studies.The main research contents are as follows:(1)Research on the scanning principle and architecture of photonic LiDAR FPSA.Based on the FPSA scanning principle,this work conducts an in-depth investigation into the overall layout of optical antennas,optical switch networks,and wavelength-division multiplexers.Two architectures are proposed:a large-scale line scanning silicon-based FPSA transmitter system and a high-power large-scale line scanning silicon nitride-based FPSA transmitter system.In the silicon-based architecture,the optical path is controlled via a network of optical switches,enabling automatic addressing to specific waveguide buses in the column direction,thereby achieving beam deflection control along the column axis.A set of?optical antennas-each composed of a power splitter and a grating coupler-transmit synchronously in the row direction,and in combination with an offchip lens,facilitate beam deflection control along the row axis.This approach allows the system to realize large-scale two-dimensional beam scanning with minimal optical switch networks.The silicon nitride-based architecture,constructed entirely with passive silicon nitride devices,eliminates the need for optical switches.It achieves column-direction beam steering by modulating the wavelength of incident light,while row-direction steering is still accomplished through the combined action of power splitters,grating couplers,and off-chip lenses.(2)Research on large-scale line scanning silicon-based FPSA transmitter system.To address the requirements of the silicon-based FPSA transmitter architecture,the system and its photonic devices were studied and optimized.First,a genetic algorithm was employed to design and optimize the grating region of the grating coupler.A novel mode converter was developed using topology optimization and on-chip metalens theory,integrating these to achieve a compact grating coupler design.Next,for the Mach–Zehnder interferometer optical switch unit,a foundational model was constructed based on multi-mode interference theory.The genetic algorithm was used to optimize the input/output ports of the multimode interferometer region,while the topology optimization algorithm was applied to refine the curved connecting waveguides.These optimizations ensured high transmission efficiency and low phase error in the final optical switch design.Furthermore,building on traditional directional couplers,topology optimization was utilized to design power splitters with varying splitting ratios,ensuring uniform optical energy distribution to the transmitting grating couplers.Finally,the design of the transmitting grating couplers incorporated considerations of coupling efficiency and mode-field matching,further enhancing the beam quality of the transmitted modes.(3)Research on high-power large-scale line scanning silicon nitride-based FPSA transmitter system.To meet the requirements of the silicon nitride-based FPSA trans-mitter architecture,the photonic devices were designed and optimized.First,based on mode-field matching principles,an inverse-tapered edge coupler and a compact multi-stage trident-type edge coupler were designed,significantly improving coupling efficiency over a broad wavelength range.For the wavelength-division multiplexer,a large-scale arrayed waveguide grating and a compact validated arrayed waveguide grating were designed,with optimizations applied to the arrayed waveguides and bent waveguides.To accommodate larger-scale transmitter arrays,a cascaded design combining arrayed waveguide gratings with multimode interference-based wavelength division multiplexers was proposed.The topology optimization algorithm was employed to design and optimize broadband multimode interference-based wavelength division multiplexers,enhancing coupling efficiency and wavelength adaptability.Additionally,by integrating deep learning and genetic algorithms,rapid design of transmitting grating couplers under different wavelengths was achieved,substantially improving design efficiency.Finally,a novel off-chip lens based on metalens simulations was designed,enabling nearly aberration-free angular steering control of light emitted from the grating couplers.(4)Testing and analysis of FPSA transmitting chip system for photonic LiDAR.Two types of photonic integrated LiDAR FPSA transmitter chips were fabricated using ultraviolet lithography and electron beam lithography techniques,and a far-field testing system for the transmitter chips was constructed in combination with an optical waveguide coupling platform.Based on the actual processing scale,an off-chip lens was designed and simulated.Far-field beam scanning tests were performed with the integration of a high-precision voltage source.By analyzing parameters such as field of view,angular resolution,divergence angle,and beam extinction ratio,the overall performance was evaluated,and the effectiveness of the two proposed architectures in practical applications was validated.更多还原