Fully three-dimensional accurate modeling of scattering loss in optical waveguides

Scattering loss in high-index-contrast optical waveguides has been modeled by a rigorous 3D numerical algorithm based on volume current method. The electromagnetic field generated by the wire current distribution simulating sidewalls roughness has been calculated by 3D finite element method. The developed modeling technique does not introduce any approximation in radiated power estimation. Numerical results obtained by our model have been compared with some experimental results reported in literature for four typical sub-micrometer high-index-contrast waveguides realized by different technologies and a very good agreement (relative error less than 3%) has been demonstrated. Closed-form expressions for scattering loss in low-index-contrast waveguides have been also derived and discussed. Developed modeling technique has been compared with other three-dimensional algorithms for scattering loss estimation and its advantages in terms of accuracy, computation time and generality have been pointed out. Scattering loss dependence on the parameters of the roughness distribution has been finally discussed.