Thin disk laser is the most successful design to overcome the degradation of the beam quality caused by the gain
medium's thermal effects and has many advantages in beam quality keeping and power scalability over the traditional
rod and slab laser. In this paper a different type thin disk laser with the large-aperture Nd:YAG disk face-pumped by
2D-stack diode arrays was presented. Over 3kW average power with the beam quality less than 10 times diffraction
limitation was achieved by optimizing the pumping optics designs and improving the gain medium mounting technique.
Thermal effects present a major challenge to scaling of solid-state laser to high-average power. When using a thin laser crystal disk with a nearly flat-top pump profile, the heat flux can be considered to be one-dimensional. This results in a homogeneous temperature and stress profile within the laser medium leading to reduction of thermal effects. The pump profile is the main factor that may affect the homogeneous temperature profile, but some other factors may affect the temperature homogeneity, such as the cooling dimension and the ratio of the pump area to the thickness of the disk. These factors are analyzed and a good design is made. An average output power of more than 120W is obtained from one single disk and that of 216W from two disks.