Quasi-continuous-wave Operation | previous | next | feedback |
Definition: an operation mode of lasers (e.g. diode bars) where the pump power is switched on for short time intervals in order to limit thermal effects
Quasi-continuous-wave (quasi-cw) operation of a laser means that its pump source is switched on only for certain time intervals, which are short enough to significantly reduce thermal effects, but still so long that the laser process is close to its steady state, i.e., the laser is optically in the state of continuous-wave operation. The duty cycle (percentage of "on" time) may e.g. be a few percent, thus strongly reducing the heating and all the related thermal effects, such as thermal lensing and damage through overheating. Therefore, quasi-cw operation allows the operation with higher output peak powers at the expense of a lower average power.
Pulsed operation with significantly shorter pumping times is called gain switching.
Quasi-continuous-wave operation is most often used with diode bars and diode stacks. Such devices are sometimes even designed specifically for quasi-cw operation: their cooling arrangement is designed for a lower amount of heat extraction, and the emitters can be more closely packed in order to obtain a higher brightness and beam quality. Compared with ordinary continuous-wave operation, additional lifetime issues can result from quasi-cw operation, related e.g. to higher optical peak intensities or to frequent temperature changes.
Some doped-insulator solid-state lasers are also operated in quasi-continuous-wave operation. Such lasers are sometimes called heat capacity lasers.
See also: continuous-wave operation, modes of laser operation, gain switching, diode bars, diode stacks
