Cr4 +: YAG crystal is an excellent passive Q-switched crystals for a large number of 1μm neodymium and ytterbium lasers. With Q-switch output high efficiency, it is suitable for repetitive frequency operation. It has a high light damage threshold and is stable and durable over dyes and color-centered saturable absorbers, which in some cases can replace the electro-optic Q-switch to output high-power laser pulses.