Cr: YAG crystal can be made use of not just as Q-switch but likewise as a gain medium as a result of its excellent physicochemical properties. The Q-switch procedure of pulse as well as CW Nd: YAG lasers have actually been recognized by using Cr4+: YAG as a Q-switch, and also the CW tunable and also self-mode-locked operation has likewise been recognized by utilizing CR4 +: YAG as a gain tool. Compared with the standard saturable absorber, Cr: YAG transcends the traditional saturable absorber in lots of facets. The doping focus of the Cr4+ ion in Cr4+: YAG is as high as 1018 cm-3, which can efficiently reduce the dimension of passive Q-switch elements. It is beneficial to achieve high optical conversion efficiency, integration, and also compact passive Q-switch laser.