Radio frequency/microwave-directed energy sources using wide bandgap SiC photoconductive semiconductors have attracted much attention due to their unique advantages of high-power output and multi-parameter adjustable ability. Over the past several years, benefitting from the sustainable innovations in laser technology and the significant progress in materials technology, megawatt-class output power electrical pulses with a flexible frequency in the P and L microwave wavebands have been achieved by photoconductive semiconductor devices. Here, we mainly summarize and review the recent progress of the high-power photonic microwave generation based on the SiC photoconductive semiconductor devices in the linear modulation mode, including the mechanism, system architecture, critical technology, and experimental demonstration of the proposed high-power photonic microwave sources. The outlooks and challenges for the future of multi-channel power synthesis development of higher power photonic microwave using wide bandgap photoconductors are also discussed.

提出了一种新的Si衬底上GaN微盘谐振腔的制备方式，避免了传统Si基GaN器件中晶体质量较差以及外延层较厚对器件性能的影响。本工作中GaN的外延生长使用蓝宝石衬底，随后将外延层转移至硅衬底上进行微盘谐振腔的制备。外延生长时靠近衬底侧的GaN富缺陷层可使用减薄抛光的方式去除，并且通过简单湿法刻蚀二氧化硅牺牲层即可实现GaN微盘与Si衬底之间的空气间隙结构。基于较好的晶体质量与低损耗的谐振腔，实现了高Q值的Si基GaN微盘谐振腔低阈值激射，阈值能量低至5.2 nJ/pulse，Q值最高为10 487。同时，器件具有较好的温度稳定特性，在100 ℃环境下也能维持低阈值激射，为大规模单片硅基光子集成提供了高性能的激光源。

垂直腔面发射激光器凭借阈值低、发散角小、调制速率高以及输出光束呈圆斑对称等特点，迅速成为当下半导体激光器的研究热点。氮化镓（GaN）材料是制造紫外到绿光波段光电子器件的理想材料，经过四十余年的研究，蓝光和绿光LED在照明、显示等领域得到广泛应用。技术含量更高的激光器件也已进入了应用的快车道，即将覆盖照明、通信、投影显示、光存储、医疗、微型原子钟及传感器等场景。铝镓氮（AlGaN）是GaN基半导体材料的重要代表之一，其禁带宽度可在3.4 eV（GaN）到6.2 eV（AlN）范围内连续可调，对应波长可覆盖200~365 nm波段，是制造从近紫外波段到深紫外波段紫外垂直腔面发射激光器的理想材料。而铝镓氮（AlGaN）垂直腔面发射激光器经过近20年来的发展，如今已成为半导体激光器的研究热点之一。首先回顾了GaN基垂直腔面发射激光器的发展历史，简要介绍了其在各个波段的主要应用场景；然后介绍蓝光、绿光及紫外垂直腔面发射激光器的研究进展；最后分析了光注入和电注入紫外垂直腔面发射激光器发展过程中的挑战和困难，并介绍了改进和优化的策略。