Optical system for variable resizing of round flat-top distributions

An optical system is described which is capable of variable resizing of a round flat-top light distribution of a highly coherent and collimated laser beam at a certain, fixed working distance. It contains cylindrical and spherical optics. First-order optics is used to analyze the system, and the second-order moments method is used to describe the beam properties. The analysis indicates the existence of an "image-mode" regime, allowing a dynamic range, or a zoom range of about (13 - 15) : 1 for resizing the diameter of the round, flat-top distribution in the target plane, by rotating one cylindrical element. Experiments using as incoming beam a collimated Ar-laser TEM00 gaussian beam reshaped to a collimated flat-top with 6.8 mm in diameter, confirm the approach, by obtaining at the target plane spot sizes with diameters continuously variable between 1.0 mm and 13.6 mm and with flat-top profiles.