Effects of thin coating on guided mode and sidewall-roughness scattering loss in slot waveguides

摘要

Considering utilizing atomic layer deposition (ALD) to depress scattering loss due to sidewall roughness in silicon-on-insulator (SOI) slot waveguides, we discuss the effects of the refractive indexes and the thicknesses of the ALD layers on the modal field, the power confinement factor and the scattering loss of the slot waveguides by numerical simulation. We demonstrate that in applying ALD the decrease of the refractive index contrast on the sidewalls is the main reason for the reduction of the scattering loss, and a single-layer coating with a lower refractive index and a double-layer coating are more effective in depressing the scattering loss. We also show that suitable design of the slot waveguide and the coating scheme is necessary to reconcile both a high confinement factor and a low scattering loss.