The invention concerns a longitudinally pumped laser comprising one or several active lasing media arranged in an optical cavity and pumping means (4) emitting at least a pump beam towards the active lasing media (3), means coupling (5) the beam(s) with the active medium. The invention is characterised in that at least one of the active lasing media comprises one or several non-homogeneously doped zones (8) and the dimension of said doped zones (8) and/or the distribution of the doping agents is selected on the basis of the desired transverse mode. Said laser is useful as amplifier.
