Internal loss is a key internal parameter for high power 1060-nm In Ga As/Al Ga As semiconductor laser.In this paper,we discuss the origin of internal loss of 1060-nm In Ga As/Ga As quantum well(QW) Al Ga As separate confinement heterostructure semiconductor laser,and the method to reduce internal loss.By light doping the n-cladding layer,and stepwise doping the p-cladding layer combined with the expanded waveguide layer,a broad area laser with internal loss of 1/cm is designed and fabricated.Ridge waveguide laser with an output power of 350 m W is obtained.The threshold current and slope efficiency near the threshold current are 20 m A and 0.8 W/A,respectively. Internal loss is a key internal parameter for high power 1060-nm In Ga As / Al Ga As semiconductor laser. In this paper, we discuss the origin of internal loss of 1060-nm In Ga As / Ga As quantum well (QW) Al Ga As separate confinement heterostructure semiconductor laser, and the method to reduce internal loss. By light doping the n-cladding layer, and stepwise doping the p-cladding layer combined with the expanded waveguide layer, a broad area laser with internal loss of 1 / cm is designed and fabricated. Ridge waveguide laser with an output power of 350 mW is obtained. The threshold current and slope efficiency near the threshold current are 20 m A and 0.8 W / A, respectively.