Hi everyone 

setting up an easy test system (sequential mode) with entrance pupil diameter and one focusing lens POP gives reasonable results (POP beam entrance set correctly to aperture value).
But adding an aperture into the system to “clean up” laser beam at 1/e² of beam diameter lets peak irradiance decrease and beam size gets wider. In normal spot diagram it looks fine (diffraction limited) with clean up aperture.

Does anyone observed same issue or has a hint?

Kind regards

Christian