An optical amplifier includes a solid state gain-element. The gain-element is pumped by pump-radiation from a diode-laser bar. The diode-laser radiation is delivered from the diode-laser bar to the gain-element entirely via a tapered light-guide which guides the radiation only in a fast-axis direction of the diode laser bar. The tapering of the light-guide reduces fast-axis divergence of the pump-radiation by about a factor of ten. The pump-radiation is delivered to the gain-element as a line of radiation homogenized in the fast-axis direction.