a diode - laser bar is mounted on water - cooled heat - sink between two ceramic sub - mounts for electrically isolating cooling - water in the heat - sink from the diode - laser bar . mounting between the two ceramic sub - mounts also provides for balancing stresses due to differences in coefficient of thermal expansion between the sub - mounts and the diode - laser bar . both sub - mounts are in thermal communication with the heat - sink for providing two - sided cooling of the diode - laser bar .