Methods, devices, and systems for double-sided cooling of laser diodes are provided. In one aspect, a laser diode assembly includes a first heat sink, a plurality of submounts spaced apart from one another on the first heat sink, a plurality of laser diodes, and a second heat sink on top sides of the plurality of laser diodes. Each laser diode includes a corresponding active layer between a first-type doped semiconductor layer and a second-type doped semiconductor layer. A bottom side of each laser diode is positioned on a different corresponding submount of the plurality of submounts. The plurality of laser diode are electrically connected in series.