A beam combining light source, comprising: a support base having a stepped surface formed of a series of parallel mounting surfaces disposed in a plurality of vertically offset levels; a first row of light emitters (20a,20b,20c) mounted upon the support base configured to emit a plurality of first emitter beams (33a,33b,33c) along a plurality of optical paths, each of the first emitter beams having a fast axis and a slow axis; a first row of beam collimating reflectors mounted upon the support base configured to collimate each of the first emitter beams in a plane of the slow axis thereof, and to re-direct the first emitter beams to mutually align the fast axes thereof for forming a first combined beam by stacking of the first emitter beams in the fast axis direction, wherein the first row of beam collimating reflectors (26a,26b,26c) is disposed at a distance from the first row of light emitters defining a space therebetween; a second row of light emitters (20d,20e,20f) mounted upon the support base configured to emit a plurality of second emitter beams (33d,33e,33f) along a plurality of optical paths, each of the second emitter beams having a fast axis and a slow axis; and a second row of beam collimating reflectors (26d,26e,26f) mounted upon the support base and spaced apart from the second row of light emitters configured to collimate each of the second emitter beams in a slow axis plane, and to re-direct the second emitter beams to mutually align the fast axes thereof for forming a second combined beam by stacking of the second emitter beams in the fast axis direction, wherein: light emitters of the first and second rows are disposed in an interleaved arrangement with a lateral offset between light emitters of the first and second rows mounted upon a same mounting surface with respect to a first axis that is parallel to the slow axis of each of the first emitter beams, the second row of beam collimating reflectors is disposed in the space between the first row of light emitters and the first row of beam collimating reflectors with respect to a second axis orthogonal to the fast axis and the slow axis of each of the first emitter beams, and the lateral offset between the first and second rows of the light emitters is such that the second row of beam collimating reflectors do not block any of the first emitter beams. a support base having a stepped surface formed of a series of parallel mounting surfaces disposed in a plurality of vertically offset levels; a first row of light emitters (20a,20b,20c) mounted upon the support base configured to emit a plurality of first emitter beams (33a,33b,33c) along a plurality of optical paths, each of the first emitter beams having a fast axis and a slow axis; a first row of beam collimating reflectors mounted upon the support base configured to collimate each of the first emitter beams in a plane of the slow axis thereof, and to re-direct the first emitter beams to mutually align the fast axes thereof for forming a first combined beam by stacking of the first emitter beams in the fast axis direction, wherein the first row of beam collimating reflectors (26a,26b,26c) is disposed at a distance from the first row of light emitters defining a space therebetween; a second row of light emitters (20d,20e,20f) mounted upon the support base configured to emit a plurality of second emitter beams (33d,33e,33f) along a plurality of optical paths, each of the second emitter beams having a fast axis and a slow axis; and a second row of beam collimating reflectors (26d,26e,26f) mounted upon the support base and spaced apart from the second row of light emitters configured to collimate each of the second emitter beams in a slow axis plane, and to re-direct the second emitter beams to mutually align the fast axes thereof for forming a second combined beam by stacking of the second emitter beams in the fast axis direction, wherein: light emitters of the first and second rows are disposed in an interleaved arrangement with a lateral offset between light emitters of the first and second rows mounted upon a same mounting surface with respect to a first axis that is parallel to the slow axis of each of the first emitter beams, the second row of beam collimating reflectors is disposed in the space between the first row of light emitters and the first row of beam collimating reflectors with respect to a second axis orthogonal to the fast axis and the slow axis of each of the first emitter beams, and the lateral offset between the first and second rows of the light emitters is such that the second row of beam collimating reflectors do not block any of the first emitter beams. light emitters of the first and second rows are disposed in an interleaved arrangement with a lateral offset between light emitters of the first and second rows mounted upon a same mounting surface with respect to a first axis that is parallel to the slow axis of each of the first emitter beams, the second row of beam collimating reflectors is disposed in the space between the first row of light emitters and the first row of beam collimating reflectors with respect to a second axis orthogonal to the fast axis and the slow axis of each of the first emitter beams, and the lateral offset between the first and second rows of the light emitters is such that the second row of beam collimating reflectors do not block any of the first emitter beams.