The present invention is related to laser technology which enables efficient, passive, coherent beam combination from distributed gain sources. The present invention includes a novel architecture which coherently combines the power from multiple sources, and which adds considerable flexibility to laser gain materials for many applications. The novel architecture of the present invention combines two techniques: 1) beam splitting and combination; and 2) phase-locking (i.e., maintaining a common phase relationship between multiple beams), using reflective gratings. Thus, the present invention addresses important limitations in laser technology: efficiency, power scaling and wavelength selectivity.