中心博士生秦睿恒同学的工作——Towards Direct Sampling of Ultra-Broadband Microwave Signals: A Review of Integrated Photonic Analog-to-Digital Converter Technologies（面向超宽带微波信号的直接采样：集成光子模数转换器技术综述）的相关成果最近被Journal of Lightwave Technology期刊接收，该工作得到了国家自然科学基金（T2225023, 62205202, 62205203）以及上海市青年科技英才扬帆计划（No. 22YF1420200）的部分资助。
现有的基于传统电学技术的高速宽带射频信号数字化方案在带宽和速率方面已逐渐无法满足新一代高性能信号采集的需求。为实现更低抖动、更高带宽、多路复用的新型信号采集系统，本工作系统性回顾了光子模数转换器（PADC）的基本原理与近五十年来的研究进展。本文基于光子技术在信号数字化过程中的作用，将现有PADC技术方案分为四大类：光辅助型PADC、电采样光量化型PADC、光采样电量化型PADC，以及全光采样量化型PADC。
在此基础上，本文进一步聚焦于光采样电量化型PADC架构，该方案因其集成化进展迅速及在直接射频采样中的广泛应用，成为当前学术研究的热点。该方案通过集成电光调制器、光学复用网络和光电探测器等光子元件，以及光电协同的模块化封装设计，实现了100 GHz以上的模拟带宽，8-14位的分辨率，从而有效突破传统电子接收系统瓶颈。本工作系统分析了不同架构的光采样电量化型PADC的集成化成果及其在雷达和通信等典型应用场景的实际表现，并评估了其对下一代信号采集处理的变革性影响。
最后，本文分析总结了现阶段PADC技术发展面临的集成化与高性能化挑战，并针对未来PADC技术的发展方向提出了潜在解决策略与前瞻性展望。
摘要:
Photonic analog-to-digital converters (PADCs) have been investigated for nearly five decades as a promising solution for next-generation high-performance signal acquisition, thanks to their inherent advantages such as low jitter, high bandwidth, and unique multiplexing techniques. This paper reviews the fundamental principles and recent advancements in four well-known categories of PADCs based on the role of photonic technology in the signal digitization process: photonic assisted PADCs, electronic sampling and photonic quantizing PADCs, photonic sampling and electronic quantizing PADCs, and photonic sampling and quantizing PADCs. We then focus on photonic sampling and electronic quantizing PADCs, which have emerged as the most widely used architecture, owing to their rapid integration progress and practical applications in direct RF sampling. This architecture overcomes the limitations of electronic systems by achieving bandwidths exceeding 100 GHz while maintaining a resolution of 8-14 bits. The modular design, which integrates optical components like modulators, optical demultiplexers, and photodetectors with chiplet-based photonic-electronic co-packaging, holds great potential for hybrid integration and monolithic implementation. Demonstrated in direct RF sampling applications, such as radar and communication systems with >8 GHz instantaneous bandwidth, these PADCs offer a transformative solution for next-generation signal acquisition and processing. Furthermore, this paper reviews the latest integration results of these PADC architectures and their applications in radar and communication systems. In the end, acknowledging the existing challenges, we highlight potential strategies and provide insights into the future development of PADCs for integration and direct RF sampling applications.