Excitation unti fir a fiber laser

A fiber laser including an excitation unit, said excitation unit comprising:

• at least one excitation fiber which has a longitudinal axis and which forms a two-dimensional or three-dimensional structure in a resonator region of the fiber laser, the excitation fiber, when viewed in cross-section, including an active fiber core, a pump cladding that surrounds the active core, a quartz glass casing that surrounds the pump cladding, a silicon buffer that surrounds the quartz glass casing and a cover;
• and
• the resonator region being equipped with a base plate on which a plurality of excitation housings are provided, each forming a gas-tight excitation chamber, the excitation fiber running through each excitation chamber at least once and being held in holding units laterally to each excitation chamber when viewed in the longitudinal axis of the excitation fiber, the cover of the excitation fiber being removed in the excitation chambers and being completely present in the regions of the holding units, the excitation fiber having a first fiber end which serves as a reflector element, and a second fiber end which serves as an out-coupling mirror element, wherein
• a) the excitation chambers are elliptically formed in a cross-section perpendicular to the longitudinal axis of the excitation fiber,
• b) the excitation housings are provided with a translucent housing window, and
• c) a transverse pump light source is arranged in the region of each translucent housing window such that a pump beam that leaves the pump light source impinges onto the longitudinal axis of the excitation fiber preferably in a perpendicular manner.