Laser beam characterization and measurement techniques

For the application of high-power lasers in materials processing beam parameters are needed which should correlate with the processing result, should make it predictable for the user and should allow simple lay- out calculations for beam-guiding and beam-shaping equipment. Two methods for beam-radius characterization which are currently under consideration are discussed and compared: the 86%- radius and the momentum-radius. Although the 86%- radius can be used in many practically relevant cases with acceptable errors, for an extended beam- characterization use of the momentum method seems to be advantageous. Current investgations are discussed which are aiming to the reduction of problems with unknown powerenclosure and integrals diverging for practically relevant intensity distributions and which are using higher-order momentum parameteres describing the beam in greater detail. For the 86% - as well as the momnentum-method careful control of the measurement conditions is necessary in order to achieve appropriate accuracy in practice. A discussion of typical measurement errors is included as well as a presentation of measurement equipment.