Abstract: Methods and apparatus for side pumping lasers are disclosed. By pre-collimating radiation emitted by laser diode arrays, the present invention provides transverse mode matching to achieve fundamental, or TEM.sub.00, mode operation in the corresponding (nominally vertical) axis. Optics associated with the resonant cavity additionally redirect energy longitudinally through the gain media, enhancing fundamental mode operation in the (nominally horizontal) other axis as well. With dual forty-watt linear arrays of laser diodes and four longitudinal passes, TEM.sub.00 mode outputs exceeding fifteen watts have been achieved.