Relationship between beam quality and power for solid state laser with high average power

One of the primary development orientations of solid state lasers is to realize the output with '3 highs' which is high average power, high beam quality and high efficiency. By combining the related research works and progress of solid state laser, the authors dissertate on the relationship of beam quality and output power for solid state laser , and the fundamental scientific question that the beam quality nonlinearly decreases with the power increase is suggested. Some important techniques to solve the problems are reviewed and the possible and effective approaches to obtain the '3 highs' solid state laser are probed. (authors)