c

radiating dipoles excited by the guided light. In our 2-D appro (Fig. 1, in larization 1550 nm. ness at th loss of an that irreg whe tion reca irre can slab ithLtot P yLydy, (1) re P y is the scattered power of the dipole at posi-y and Ly is the fraction of that power that is not ptured by the waveguide. Although scattering at gularities should be treated in a coherent way, we use this incoherent integration as a figure of merit, Fig. 1. Geometry of an air slot with roughness in a waveguide. Waveguide core width dcore changes w cladding index nclad for a constant v number.ximation we use air slots in a slab waveguide set). The simulations were made for TE po-(E f ield parallel to the layer interfaces) at The total power lost that is due to rough-e sidewall will be proportional to the power irregularity averaged over any position y of ularity along the interface:ZScattering at sidewall rough