Influence of the layer design on the far field pattern in GaN based laser structures

The waveguiding properties of nitride laser diodes are investigated for different Al concentrations in the cladding layers by calculating the optical field inside and by measuring the far field pattern behind the structures. The thicknesses of the p-cladding layer and of the electron blocking layer are also taken into account. The best optical confinement is reached for 10% and 12% Al in the n- and p-cladding layer, respectively. For these Al concentrations the full width at half maximum of the intensity distribution in the far field is increased by 15%. To prevent the leaking of the optical mode into the p-GaN cap layer the p-cladding layer should not be thinner than 270 nm.