The operating characteristics of Al-free InGaAsP/GaAs separate confinement heterostructure single quantum well high power laser grown by low-pressure metalorganic chemical vapor deposition are reported. The internal differential quantum efficiency η i is closed 98 percent. The external differential quantum efficiency η d of 75 percent and characteristics temperature T o of 146 degrees C are achieved, CW total output power both facets of 2.6 W single quantum well laser with 100 μm width, 1.1 mm cavity length is obtained. Threshold current density J th, reciprocal differential quantum efficiency l/η d, emission wavelength λ and characteristics temperature T o as function of laser cavity length L respectively have been measured and researched. Dependence of J th (T), λ (T), and η d (T) respectively on temperature T have been given and explained.