Two-dimensional optical waveguide mode simulations have been employed to investigate the optimized device structures for ridge-waveguide (Al, In, Ga) N-based green (520 nm) laser diodes (LDs). The effects of thicknesses, alloy compositions, and doping densities of each epitaxially grown layers as well as ridge geometries on optical confinement factors (α) and waveguide absorption (α) were comprehensively surveyed. Iny Ga 1-y N (y=0.07-0.1) guiding layers (GLs) with thickness more than 50 nm were effective for realizing high and low α. To minimize the absorption by the anode metal, p -cladding layer (p-CL) was required to be more than 500 nm. At the same time, low index insulator such as SiO2 was preferable for the narrow ridge, where the thickness at the sidewall had to be more than 60 nm. We also found that InGaN barriers layers between the quantum wells (QWs) were superior to GaN barriers to increase and reduce α. Moreover, a thicker last barrier between the topmost QW and the electron blocking layer was also effective to reduce α. Regarding the effect of Mg doping concentration on the absorption, the reduction in Mg in the p -CL and the p -GL was significant to reduce α. Generally, it was confirmed the design for typical 405 nm LDs can be applied for 520 nm LD with the inclusion of InGaN GLs and barriers for the QWs.