Beam power measurement with widening

Apparatus for the measurement of the power and/or of the energy of a laser beam, comprising a radiation sensor, an expansion device, and a support mount, wherein the radiation sensor has a receiving surface and is configured for the generation of an electrical signal, which is dependent on the power of the laser beam or the energy of the laser beam, wherein the radiation sensor comprises an absorption body and a temperature sensor, and wherein the temperature sensor is thermally coupled with the absorption body, the temperature sensor being adapted to measure a temperature of the absorption body and to generate the electrical signal, wherein the expansion device and the radiation sensor are positioned at a distance from one another on the support mount for the formation of a propagating laser beam between the expansion device and the radiation sensor, wherein the expansion device comprises a lenslet array defined by a plurality of lenslets that are all arranged in a common plane, where the lenslet array is configured in such a way as to increase the angle range of the laser beam, wherein a diameter of the laser beam propagated on the receiving surface is greater than a diameter of the laser beam in the area of the expansion device, and wherein the receiving surface of the radiation sensor encloses at least 90% of the cross-section surface of the laser beam propagated.