Abstract: A laser bar structure is mounted on a submount which includes first and second side surfaces. The first side surface has an electrically-conducting elongated mesa adjacent to the rear surface defining a placement space for a laser bar. A conducting foil connects the laser bar to the mesa. A plurality of such submounts are stacked such that the rise of the mesas provide room for the lasers and the connections to them. Each submount has a through conduit which align when stacked to form a coolant manifold. The rear surface of the stack is mounted on a microchannel cooler. A single array or a plurality of arrays are assembled electrically in series between heat conducting end blocks with fittings for connection to a coolant supply.