An optically end-pumped amplifier with a plate-shaped optical gain medium has a plurality of pump laser units for optically pumping the gain medium through at least one of the narrow side surfaces thereof. The pump laser units are designed such that the pump laser radiation, upon passing through the gain medium, has an elongated beam cross section having a short axis and a long axis running parallel to the main surfaces of the gain medium and propagates freely through the gain medium with respect to the short axis. They are arranged such that in each case the principal axes of the beam bundles of the pump laser units impinge on one of the pumped side surfaces in a plane perpendicular to the short axis at an angle to one another, wherein the beam cross sections of the beam bundles are superimposed on one another.