The invention relates to a laser amplifier system comprising a solid body having a laser-active medium, a pump radiation source for producing a pump radiation field which passes multiply through the solid body, and a focusing system which produces a plurality of different branches of the pump radiation field that enter the solid body, and in this case converts at least one branch that emerges from the solid body into one of the branches that enter the solid body and are different from the emerging branch.
Such a laser amplifier system is known from the prior art, for example from EP 0 632 551.
In these laser amplifier systems, the branch that emerges from the solid body is merely deviated and refocused onto the solid body.
The disadvantage of such a focusing system is that, with it, the cross section of the pump radiation field to be focused is always increased or significant losses arise because a part of the pump radiation field is not refocused back onto the solid body.
Overall, achieving the highest possible pump power radiation density in the solid body is problematic, especially under the premise that the greatest possible number of passes of the pump radiation field is striven for, since the absorption by the laser-active medium in the body during a single pass of the pump power is small.
It is therefore an object of the invention to improve a laser amplifier system of the generic type in such a way that the highest possible pump power density in the solid body can be achieved with the least possible outlay.