Scalable, thermally efficient pump diode systems. These systems may include an arrangement of pump diodes and thermally conductive spacers mounted within a single indentation in a substrate or substrate clamps, so as to provide enhanced heat removal from the system. These systems also may include a plurality of such pump diode assemblies mounted, in a symmetric or partially symmetric arrangement, around a lasing medium in a diode pumped laser system, to improve heat removal and/or excitation of the medium.