基于反射式微环的集成光控波束成形技术研究

Optical true time delay based on micro-ring resonators is an effective approach for integrated optical beam-former. However, the delay bandwidth limited by large group delay dispersion is a key challenge in conventional micro-ring resonator. In this project, we propose a new method based on group delay dispersion cancellation to expand the bandwidth and design a novel reflective-type micro-ring resonator. In such reflective-type micro-ring resonator, the light propagating counterclockwise is slow light, while the one propagating clockwise is fast light. Given the fact that the group delay dispersion of fast light can offset that of the slow light, the total group delay dispersion can be reduced. Hence, one can use only one micro-ring resonator to achieve continuously tunable wide-bandwidth optical true time delay. Herein, we propose and design a novel integrated optical beam-former based on cascaded reflective-type micro-ring resonators with different radii, with potential to solve common problems found in the binary-tree delay network, such as massive micro-ring resonators, larger footprint, and unequal output power. In addition, the optical single-sideband suppressed-carrier modulation can be realized without extra optical filter. As a result, our system can work in a large frequency range and become reconfigurable. To achieve our goal, we will first study the interaction between slow light and fast light in the micro-ring resonator, as well as the mechanistic insight of expanding the optical true time delay. We will then analyze the relationship between the input light wavelength and the output delay of each channel, and establish delay allocation and tuning mechanism. Finally, we will design, fabricate and test the integrated optical beam-former chip. The research finding of this project will aid the development in fields such as new generation phased array radar, multi-beam satellite antenna, and mobile communication (smart antenna).

光微环是集成光控波束成形网络实现延时控制的有效途径。针对传统微环延时带宽受限于群延时色散的关键挑战，本项目拟提出基于群延时色散对消效应拓展延时带宽的新方法，设计反射式微环新结构，利用同一微环内逆时针传播慢光和顺时针传播快光的群延时色散对消，获得连续可调大带宽光真延时。在此基础上，提出基于级联反射式微环和波分复用技术的光控波束成形新方案，解决传统树状延时分配网络微环数目多、尺寸大、输出功率不均衡等关键问题，且无需额外的光滤波器即可实现抑制载波单边带调制，从而提高系统的工作频率范围和可重构性。项目将研究反射式微环中快慢光的相互作用，阐明其实现连续可调大带宽光真延时的物理机理；研究级联反射式微环输入波长和各信道延时量的关系，掌握延时分配和调节方法；研究器件的设计制作方法，完成原型芯片的制作、测试和功能验证。研究成果可为新一代相控阵雷达、多波束卫星通信和移动通信（智能天线）的发展提供技术支持。

光控波束成形技术在卫星通信、下一代无线通信、雷达、电子战等民用和军用领域有着广泛的应用。宽带可调光延时线是光控波束成形网络中的基础功能单元。针对传统光微环延时带宽受限于群延时色散的挑战，本项目提出一种新的集成光延时单元——反射式微环，并围绕该器件以及基于光子芯片的光控波束成形网络开展研究工作。在反射式微环方面，建立了反射式微环传输线模型，仿真研究了不同耦合系数下幅度和延时的三种线型（劈裂、平顶和洛伦兹）响应，推导了幅度和延时的平顶状态条件，提出选取合适的两个耦合系数可以在平顶状态下获得不同延时。研制了相关原型器件，实验结果与理论一致。在反射式微环的研究过程中，针对微环延时调谐过程中微环波长漂移现象，提出了一种适用于马赫曾德尔型微环的调谐方式，有效避免了谐振波长的漂移问题。此外，提出并实验验证了基于多载波和单个微环的可重构微波光子滤波器/延时线方案，以及基于单个微环和无检偏铌酸锂相位调制器的可切换带通/带阻微波光子滤波器方案。在光控波束成形芯片方面，基于微环周期性延时响应，搭建了二维波束成形系统，获得了二维波束四天线阵元所需的延时量。提出了基于微环延时矩阵芯片的多波束光控波束成形方案，实验验证了基于2×2微环延时矩阵芯片的2阵元2波束成形系统。在暗室环境下，开展了基于光控波束成形芯片的相控阵天线远场方向图测试。此外还提出了基于平行相位调制器和可调光耦合器的可集成微波光子移相器方案,利用分立器件搭建了相应系统，验证了方案的可行性。为了将反射式微环宽带延时线应用于集成微波光子相控阵雷达芯片中，对微波光子雷达芯片进行了探索性研究，研制了集成微波光子雷达芯片，实现了对多普勒频移大小和方向的同时测量，并首次在世界上实现了基于微波光子雷达芯片的高分辨率雷达成像实验，成像分辨率达2.7cm。