The design and techniques of second-harmonic generation (SHG) have been well developed for lasers with low average-power or single-shot long pulse.In the high-average-power regime,however,the thermal loading may result in limited conversion efficiency and unsatisfied beam-quality due to the thermally induced phase mismatch.[1] Because of this detrimental effect,it is difficult to push SHG into the high-average power regime of a kilowatt.In order to alleviate the problem of thermally induced phase mismatch in high-averagepower SHGs,several schemes have been proposed and tested since the 1980 s,such as beam shaping and gascooled multiple-plate designs.[2-4] In another way,researchers are also attempting to seek new solutions based on the choice of nonlinear crystal.[5,6] However,this scheme of temperature-insensitive phasematching (PM) can be realized only at a specific wavelength for a certain crystal.