In this paper, a phase-change-cooled active mirror amplifier with high thermal conductivity composites is presented to
meet the thermal management requirement and the payload limit of laser amplifiers in the space environment. And a
three-dimensional transient model of solid-liquid phase cooling is developed to predict the phase change process and the
thermal effects in the active mirror amplifier, in terms of temperature, thermal stress, thermal deformation and thermal-induced
wavefront distortion. The measured transient temperature distributions agree well with the results of the
transient model, which verify the accuracy of the model. We expect that this investigation will assist in the design and
optimization of the high energy, high average power lasers.