Fibre laser assembly and method for generating high power laser radiation

Fibre laser assembly with at least:

• a doped active fibre, which comprises a first fibre portion and a second fibre portion adjoining the first fibre portion,
• a pump laser assembly for the optical pumping of the active fibre with first pump radiation at a first pump wavelength, and
• a seed laser, which emits laser radiation at a wavelength above the spectral amplification maximum of the active fibre, which is coupled into the active fibre at one end of the active fibre where the first fibre portion begins, wherein
• the fibre laser assembly comprises a device for the generation of second pump radiation, which is guided in the core of the active fibre, and has a second pump wavelength, which lies between the first pump wavelength and the wavelength of the seed laser, and
• the doping concentration of the active fibre, the power of the first pump laser assembly, and the length of the active fibre are adapted such that the active fibre absorbs the first pump radiation in the first fibre portion of the active fibre by >90%, radiation of the second pump wavelength, which propagates in the first fibre portion in the direction of the second fibre portion, is amplified in the first fibre portion by the first pump radiation so as to generate the second pump radiation, and the laser radiation of the seed laser is amplified by the second pump radiation in the remaining second fibre portion of the active fibre.