Various claims of a multi-laser system are disclosed. In some claims, the multi-laser system includes a plurality of lasers, a plurality of laser beams, a beam positioning system, a thermally stable enclosure, and a temperature controller. Various claims of an optical system for directing light for optical measurements such laser-induced fluorescence and spectroscopic analysis are disclosed. In some claims, the optical system includes a beam shaping element configured to generate an illumination profile having a flat top.