Method for determining at least one beam propagation parameter of a laser beam

A method for determining at least one beam propagation parameter of a laser beam, the method comprising:

• directing the laser beam through a lens arrangement towards a spatially resolving detector,
• imaging the laser beam at a plurality of different focus positions relative to the spatially resolving detector by adjusting a focal length of the lens arrangement, and
• determining the at least one beam propagation parameter by evaluating an intensity distribution of the laser beam on the spatially resolving detector at the plurality of different focus positions, characterized in that adjusting the focal length of the lens arrangement comprises arranging lens elements having different focal lengths from at least one position out of a beam path of the laser beam to at least one position in the beam path of the laser beam,
• wherein the lens elements are chosen from a set of lenses having discrete focal lengths,
• wherein the lens arrangement comprises:
• a first carrier comprising at least one accommodation space that defines a first partially enclosed region within the first carrier, wherein the first partially enclosed region includes a lens element;
• and
• a second carrier comprising at least one accommodation space that defines a second partially enclosed region within the second carrier, wherein the second partially enclosed region includes one or more attenuation elements and does not include any lens elements;
• and
• wherein the attenuation elements are transmissive optical elements made of a material having a pre-defined absorption level.