With thin disk laser under intensive pumping high heat flux go through the bonding area with voids inside it will introduce local temperature and stress increase in high-reflective(HR) coating above bonding layer. This will influence the laser damage threshold(LDTH) of local HR coating. An analytical model is developed to analyze the HR coating of thin disk laser illuminated by high fluence pulse laser considering crystal pumping and void inside bonding layer. Analytical results show that the area of HR coating is stressed and heated under crystal pumping. When illuminated by high fluence pulse laser the coating at this area has higher thermal stress. With pump density of 5kW/cm<sup>2</sup> if the radius of the void is larger than 100um the LDTH of HR coating will be affected by the void significantly. And the larger the void size is the lower the LDTH of HR coating is. Relative lower laser damage threshold of HR coating above bonding void is testified by experiment.
A SESAM mode-locked Yb:YAG thin disk laser was designed and analyzed based on the conjugated dual parabolic mirrors multi-pass pumping scheme. In the experiment, 3.6W mode-locked pulses were obtained at the repetition rate of 38.3MHz with a 5% transmission output coupler at 1030 nm. And the phenomenon of double pulses and chaotic-QML were observed in the high pumping power. Moreover, it was found that the pumping power range of the CW modelocking was very narrow in our experiment.
Fiber cladding mode stripper is one of key devices in high-power fiber lasers and high-power transmission fiber. We report a new kind of mode stripper using quartz tubes with etched dots on the surface. We studied the waveguide property of the mode stripper both the dots on the outer surface and on the inner surface of the tube. Then we produced some quartz tubes using green laser for the experiments, which demonstrated that the new model strippers can reduce the cladding light and improve the axial temperature distribution obviously.