What does laser continuous pulse operation depend on?

Some laser applications rely on beams whose output power is constant over time. This high powered laser is called a continuous wave (CW). Many types of lasers can be designed to operate in continuous wave mode for such applications. Many of these lasers operate in several longitudinal modes at the same time, and the beats between the slightly different optical frequencies of these oscillations actually produce amplitude variations on a shorter time scale than the round-trip time (the reciprocal of the frequency interval between modes), usually a few nanoseconds or less. For continuous wave operation, the particle number inversion of the gain medium needs to be continuously supplemented by a stable pump source. In some laser media, this is not possible. In some other lasers, the laser must be pumped to very high continuous power levels, which would be impractical or would damage the laser by generating too much heat. These lasers cannot operate in CW mode.