稀薄燃烧是一种先进的燃烧方法，采用稀薄燃烧技术可以使发动机在减少废气排放的同时提高热效率。稀薄燃烧催发了激光点火技术的应用。最近几十年，脉冲宽度短、峰值功率高的被动调Q 固体激光器得到了飞速的发展，特别是采用掺钕离子(Nd3+ )和镱离子(Yb3+ )的激光材料作为激光增益介质，用Cr4+∶YAG 作为被动调Q 开关的微片固体激光器在激光点火研究方面取得了长足的进展。系统地介绍了激光点火的机理和应用于激光点火的基于Nd∶YAG/Cr4+∶YAG 与Yb∶YAG/Cr4+∶YAG 的被动调Q 固体激光器的最新研究进展，以及两类被动调Q 激光器在激光点火应用中的优缺点，并指出了Yb∶YAG/Cr4+∶YAG 被动调Q 微片激光器在激光点火应用中的优势、需解决的问题及发展方向。

Laser ignition technology emerges as an advanced combustion method for engine. It can make the engine reduce waste gas emission and improve the thermal effect. Lean burning improves thermal efficiency and reduces exhaust emissions by laser ignition. In recent decades, short pulse, high peak power passively Q-switched solid-state lasers are developed rapidly for their potential applications in laser ignition. Especially the passively Q-switched lasers using neodymium ion (Nd3+) or ytterbium ion (Yb3+) doped materials as the laser gain media and Cr4+∶YAG as the saturable absorber, make much progress in potential laser ignition applications. We overviewe the mechanism of laser ignition and progresses in passively Q-switched solid-state lasers based on Nd∶YAG/Cr4+∶YAG and Yb∶YAG/Cr4+∶YAG. And the advantages and disadvantages of these two types passively Q-switched lasers used in laser ignition are discussed systematically. The advantages of Yb∶YAG/Cr4+∶YAG passively Q-switched microchip lasers used in laser ignition are addressed for future application in engine ignition. And the key issues for developing high peak power Yb∶YAG/Cr4+∶YAG passively Q-switched microchip lasers are also addressed.