A high-quality 2 μm ultrafast laser is successfully developed using a zirconium pentatelluride saturable absorber mirror (ZrTe₅-SAM) composed of a layered structure of ZrTe₅. Continuous wave mode-locked (CWML) operation has been demonstrated in the fabricated laser with Tm:YAG ceramic as the laser gain medium. Ultrafast pulses as short as 4.8 ps are obtained with a maximum average output power of 767 mW and a repetition frequency of 56 MHz, at a central wavelength of 2014 nm. To the best of our knowledge, this is the highest average output power achieved so far, for a passively mode-locked laser at 2 μm using a two-dimensional (2D) saturable absorber (SA). This study opens new doors for the development of high power 2 μm ultrafast lasers.

A passively Q-switched compact dual-wavelength Er: SrF₂ laser, operating at a 2729.73 nm and 2747.2 nm wavelength, was demonstrated by utilizing CsPbCl₃ quantum dots (QDs) as a saturable absorber (SA). The maximum average output power with the shortest duration of 510 ns and a repetition rate of 45 kHz was achieved at 190 mW, and the corresponding maximum single pulse energy and the peak power were 73.69 μJ and 141.7 W, respectively. The results present an efficient dual-wavelength laser source, and the halogen perovskite quantum dot has the potential to be employed as an excellent saturable absorber in mid-infrared pulsed solid-state lasers.

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 (PQS) Er:YAP laser at ∼3 μm with the two-dimensional saturable absorber (SA) tin diselenide (SnSe₂) nanosheet as SA was successfully demonstrated for the first time. Under the maximum absorbed pump power of 4.0 W, the obtained continuous-wave maximum output power of Er:YAP laser was 258 mW with a corresponding slop efficiency of 7.18%. In the PQS experiment, laser pulses with the shortest pulse duration of 198 ns were yielded with a repetition rate of 317 kHz under the maximum absorbed pump power of 4.0 W, and the corresponding single pulse energy and pulse peak power were 0.66 µJ and 3.3 W, respectively. The investigation indicates that SnSe₂ has the potential to be an outstanding laser modulator for PQS solid-state laser at 3 μm wavelength.

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.