In a solid-state laser amplifier including at least two laser-active media
in a common laser radiation field, the laser-active media do not form a
hard aperture for the laser radiation field. Each of the laser-active
media define a plane that is penetrated by the laser radiation field. The
laser amplifier includes at least one focusing optical element disposed
in the laser radiation field between two adjacent laser-active media. A
focal length and a distance of the focusing optical element from the
planes of the two adjacent laser-active media are selected such that the
planes of the laser-active media are approximately mapped onto each other
by a near-field far-field transformation.