A high power continuous-wave deep blue laser at 447 nm is obtained by using a doubly cavity and a type critical phase matching KTP crystal for intracavity sum-frequency-mixing. With the incident pump power of 240 W for the Nd:YAP crystal and 120 W for the other Nd:YAP crystal, the deep blue laser output of 5.7 W at 447 nm with near fundamental mode is obtained, and the beam quality M<sup>2</sup> value equals 2.53 in both horizontal and vertical directions at the maximum output power. The power s
