Hidden mechanism of mode locking for solid-state lasers using a slow off-resonant saturable absorber

There are two types of the traditional passive mode locking by saturable absorbers. Slow saturable absorbers with a longer response time than the pulse duration work very efficiently in dye lasers, and the mechanism of pulse generation in this case is characterized by the combined effects of slow saturation of the absorption and the gain, which imposes severe constraints on the laser parameters. The solid-state laser does not satisfy this conditions, and pulse generation by this type of laser demands a fast saturable-absorberlike action.