Design of diode laser using slab coupled optical waveguide with graded refractive index structure

•Improvement of slab coupled optical waveguide laser characteristics is main target.•Optical Power, Power conversion efficiency and slope efficiency were evaluated.•Graded refractive index and Graded dopant is proposed for slab layer.•The asymmetric barrier was used for increasing of internal quantum efficiency.•The cavity length was optimized for power conversion efficiency. Thickness and refractive index of slab layer have major effects in the electro-optical characteristics of slab coupled optical waveguide diode lasers. In this research, ordinary step refractive index profile was replaced by a broadened waveguide with linear graded refractive index profile and optimized doping. The results show such design can significantly improve the power conversion efficiency (PCE). According to these results, by using the asymmetric barrier in the sides of active region, the threshold current decreases and slop efficiency (SE) increases. The PCE and SE in the proposed structure are respectively 12% and 0.21 W/A higher than those in conventional step profile.