Focusing, collimation and beam shaping by active GRIN rod lenses: Theory and simulation

► We propose active GRIN rods as extra-cavity compact laser beam shaping elements. ► Active GRIN materials work like quadratic phase transformers with a Gaussian mask. ► General conditions to obtain optical functions by active GRIN rods are determined. ► We evaluate irradiance and beam parameters evolution in active GRIN rod lenses. ► Simulation of uniform beams by active GRIN rod lenses is presented.