Working-Mode Expansion of Active-Trigger Bleached Nd:YAG/Cr⁴⁺:YAG Passive Q-Switched Lasers

This study proposed a working mode incorporating the light control module parameters into the initial design of active-trigger bleached Nd:YAG/Cr $^{\mathbf {4+}}$ : YAG passive Q-switched lasers to extend their functionality. The proposed mode, named Type I mode, generates a pulse with a pumping power lower than the passive mode threshold, while the traditional setup is referred as Type II mode. The universality and implementation of the two working modes are verified experimentally, and the pulse characteristics are determined. The results demonstrate that Type I mode has high performance and low jitter pulses, similar to the Type II mode. Furthermore, Type I mode outperforms the passive mode and can reach the low-frequency region, unlike the Type II mode, which has no frequency lower bound and can be triggered manually. These advantages and the low power consumption make laser devices working in the Type I mode a high-quality light source for remote sensing and long-range communication, especially for space applications.