InGaAs/GaAs/AlGaAs material high power diode lasers with large optical cavity (LOC) have been reported. Based on the solution to the intrinsic equation of quantum well energy level, In content of the InGaAs quantum well layer was optimized; the output beam divergence and optical power density on facets were reduced effectively by using LOC structure for high power, low beam divergence output. The designed 940 nm wavelength laser structure has been obtained by successful molecular beam epitaxy (MBE) growth with a low threshold current. The finally prepared devices reached up to 2 W power output with a low threshould current of 300 mA. The beam divergence of θ∥ and θ⊥ is 10° and 30° respectively and the peak wavelength of the lasing devices is 939.4 nm.