Light-source including a planar array of diode-laser bars

A light-source includes a planar array of diode-laser bars and a plurality of turning-mirrors arranged to stack beams from the diode-laser bars in the fast-axis direction to provide a first combined beam. Six plane mirrors are arranged to divide the combined beam into three beam-slices, each having one-third the slow-axis width of the first combined beam, and add the beam-slices in the fast-axis direction to provide a second combined beam having about one-third the slow-axis width and three-times the fast-axis length of those of the first combined beam. A spherical mirror and a cylindrical mirror focus the second combined beam into an optical fiber.