Numerical analysis of the radiation losses due to surface roughness in integrated optics devices

A numerical model of the surface roughness is simply implemented into the beam propagation method to estimate the radiation losses in integrated optics devices. In this model, the deviation variables of the surface stem from a random generation controlled by the distribution function, and the spacing of deviations on the surface is determined considering their correlation length. The radiation losses due to surface roughness for a planar waveguide are estimated through this model using the FD-BPM scheme and are favorably compared with the ones obtained by another method reported in literature. For a 45 degrees self-aligned integrated mirror made on a dielectric waveguide, the calculated radiation losses agree well with the measured ones.