Laser-induced acoustic (LIA) underwater detection, as a next-generation sensing paradigm, combines high spatial resolution, rapid temporal response, and cross-medium detection capability, positioning it as a strategically significant technology in marine resource exploration, military security, and ocean environmental monitoring. The fundamental principles underlying LIA technology are systematically examined, together with recent advances in representative experimental systems and critical enabling techniques. The characteristics of the laser–acoustic transmission channel are comprehensively investigated, and the mechanisms through which laser parameters modulate the properties of acoustic signals are rigorously elucidated. Moreover, several challenges hindering practical applications are underscored, including laser energy attenuation, interference arising from complex underwater environments, and the comparatively high cost of equipment. Finally, future research directions are outlined, encompassing the development of high-efficiency laser sources, multimodal integrated sensing strategies, intelligent signal processing algorithms, and improved environmental adaptability. These efforts are intended to provide theoretical underpinnings for the continued advancement and broader application of LIA-based underwater detection technologies.

A passively Q-switched Er:YAP laser of 2.7 µm, utilizing Au-doped CsPbI₃ quantum dots (QDs) as a saturable absorber (SA), was realized. It was operated stably with a minimum pulse width of 185 ns and a maximum repetition rate of 480 kHz. The maximum pulse energy and the maximum peak power were 0.6 μJ and 2.9 W, respectively, in the Q-switched operation. The results show that the CsPbI₃ QDs SA exhibits remarkable laser modulation properties at ~3 μm.