The present invention relates to a laser system and a method of generating a defined spatial mode-shaped laser beam using an unstable laser resonator layout. The laser system for mode shaping of a laser beam within an unstable optical resonator layout comprising an active medium, characterized in that, the active media comprises a pumped area, wherein the gain distribution is generated by an optical pump beam's spatially intensity profile.
In a preferred embodiment, the system may further comprise an end-pumped layout to deliver the spatially shaped optical pump beam to the active medium; and/or an active element and/or a passive element for modifying the resonator losses; and/or means of output coupling of a laser beam from said unstable resonator layout.
The system according to the present invention is suitable to deliver a top-hat beam profile.