Light beams from multiple emitters, such as lasers, arranged in two or more arrays are combined by beam-superposition using a dispersive element, such as a diffraction grating, to provide a combined output beam with increased power. Each emitter produces light of a controlled wavelength that is incident upon the diffraction grating at a corresponding selected incidence angle to produce a diffracted wave that propagates in an output direction and forms a component of the combined output beam. First and second arrays are located on opposing sides of the combined output beam and are arranged such that light from all of the emitters overlaps to form the combined output beam. The wavelengths may be controlled by an external resonator, for example. As many as four arrays may be combined using a two-dimensional diffraction grating.