Apparatus include a conductive block including a base surface and a plurality of parallel stepped surfaces opposite the base surface and defining respective mounting surfaces situated to receive respective laser diodes having respective thermal paths defining a common thermal path distance from the mounting surfaces to the base surface, and a two-phase cooling unit including a coupling surface attached to the base surface of the conductive block and wherein the two-phase cooling unit is situated to conduct heat generated through the emission of laser beams from the laser diodes along the thermal paths.