A low-order wavefront aberration self-compensation high power Nd:YAG slab laser module is developed and demonstrated. By numerical simulating the thermal distribution and transmission wavefront of the slab laser medium, a thermally-compensated heat removal geometry is developed to reduce the wavefront distortion. This method allows the non-uniform cooling to flatten the thermal gradient ... [Show full abstract] distribution in the width direction of the slab. By using the optimized gain module as an amplifier, the laser output power of 7.8 kW is achieved. Compared to the traditional module, the output power is 7.3 kW, and the peak-to-valley (PV) value of the wavefront distortion is reduced from 17.21 to
under full power, the beam quality factor
is improved from 12.7 to 3.5 times diffraction limited while without additional correction system.