Laser assembly with spectral beam combining

A laser assembly (1210) for generating an assembly output beam (1212) includes a laser subassembly (1216) that emits a plurality of spaced apart first laser beams (1220A), a plurality of spaced apart second laser beams (1220B), a transform lens assembly (1244), a wavelength selective beam combiner (1246), and a path length adjuster (1299). The transform lens assembly (1244) collimates and directs the laser beams (1220A) (1220B) to spatially overlap at a focal plane of the transform lens assembly (1244). The path length adjuster (1299) is positioned in a path of the first laser beams (1220A), the path length adjuster (1299) being adjustable to adjust of a path length the first laser beams (1220A) relative to the second laser beams (1220B).