Power scaling

Power scaling of a laser is increasing its output power without changing the geometry, shape, or principle of operation. Power scalability is considered an important advantage in a laser design.

Usually, power scaling requires a more powerful pump source, stronger cooling, and an increase in size. It may also require reduction of the background loss in the laser resonator and, in particular, in the gain medium.

The most popular way of achieving power scalability is the "MOPA" (Master Oscillator Power Amplifier) approach. The master oscillator produces a highly coherent beam, and an optical amplifier is used to increase the power of the beam while preserving its main properties. The master oscillator has no need to be powerful, and has no need to operate at high efficiency because the efficiency is determined mainly by the power amplifier. The combination of several laser amplifiers seeded by a common master oscillator is essential concept of the High Power Laser Energy Research Facility.

One type of solid-state laser designed for good power scaling is the disk laser (or "active mirror"). Such lasers are believed to be scalable to a power of several kilowatts from a single active element in continuous-wave operation. Perhaps, the expectations for power scalability of disk lasers is a little bit exaggerated: some of publications in favor of disk laser just repeat each other; compare, for example and; these articles differ with only titles.

Amplified spontaneous emission, overheating and round-trip loss seem to be the most important processes that limit the power of disk lasers. For future power scaling, the reduction of the round-trip loss and/or combining of several active elements is required.

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