Active–passive mode-locking using Cr:YAG crystal as saturable absorber

Cr⁴⁺ : YAG crystal was used as a saturable absorber in an active–passive mode-locked Nd : YAG laser. The stable and complete mode-locked pulse train was achieved at 1064 nm. The duration of a single pulse was obtained from 0.8 to 2.4 ns by changing the Cr⁴⁺ : YAG crystal with different initial transmission, when there was the shortest pulse width. The mode-locking dynamic process of Cr⁴⁺ : YAG crystal was analyzed by the rate equations to explain the experimental result, and the effect of excited-state absorption was considered.