A comprehensive design optimization of 1.55- m high power In GaAsP/In P board area lasers is performed aiming at increasing the internal quantum efficiency (ηi) while maintaining the low internal loss (αi) of the device, thereby achieving high power operation. Four different waveguide structures of broad area lasers were fabricated and characterized in depth. Through theoretical analysis and experiment verifications, we show that laser structures with stepped waveguide and thin upper separate confinement layer will result in high áiand overall slope efficiency. A continuous wave (CW) single side output power of 160 m W was obtained for an uncoated laser with a 50-μm active area width and 1 mm cavity length. A comprehensive design optimization of 1.55-m high power In GaAsP / In P board area lasers is performed aiming at increasing the internal quantum efficiency (ηi) while maintaining the low internal loss (αi) of the device, achieving achieving high power operation. Four different waveguide structures of broad area lasers were fabricated and characterized in depth. Through theoretical analysis and experiment verifications, we show that laser structures with stepped waveguide and thin upper separate confinement layer will result in high áiand overall slope efficiency. A continuous wave (CW) single side output power of 160 m W was obtained for an uncoated laser with a 50-μm active area width and 1 mm cavity length.