Surface roughness and backscattering.

Surface roughness is normally considered to be the main cause of attenuation in intergrated-optics glass waveguides. Previous analyses have concentrated on scattering of light into the radiation field; in fact, depending on the roughness length scale, scattering can be predominantly in the backward direction, raising the question of how important the coupling with the backward-directed bound mode is. We investigate this effect and show that it can be neglected in most circumstances.