Abstract: An apparatus for optically pumping a laser-active solid body with pumping light coupled into the solid body through an end surface of the solid body is disclosed. The apparatus includes a laser-active solid body including an end surface though which pumping light is coupled into the solid body and a lateral surface through which pumping light exits the solid body, a reflector surrounding the laser-active solid body at a distance from the lateral surface of the solid body for reflecting light that exists the solid body back towards the solid body, and a surface for diffusing light that is coupled into the solid body through the end surface of the solid body and that exits the solid body through the lateral surface. The surface is selected from the group consisting of the lateral surface and a surface of the reflector.