Abstract: A method and apparatus for laser diode bar assembly. A stacked array embodiment provides for efficient cooling of the diode bars and electrical connection between diode bars while maximizing alignment of the diode bars. The spacers are connected to a conductive surface on a heat spreader. In the stacked array, one or more diode bars are alternated in series with two or more conductive spacers, with a series circuit provided from diode bar to diode bar. The spacers hold the diodes spaced apart from insulating grooves in the conductive layer on the substrate. Alternatively, thermally conductive separator fins extend from the heat spreader substrate to contact the diode bars situated between the spacers to promote rapid heat transfer from the diodes while maintaining the diode bars electrically isolated from the conductive layer on the substrate. An apparatus and method are provided for assembling the stacked array assembly.