Roughness, inhomogeneity, and integrated optics

Surface roughness (and more generally) inhomogeneity is a constraining factor on optoelectronics devices. Its more conspicuous effect is to scatter light thus leading to power attenuation, This effect partly explains the five orders of magnitude difference in attenuation between fibers and integrated waveguides, Less well known is the effect of roughness on back-coupling and mode coupling in devices such as couplers and gratings, I present here an overview of these effect analyzed from a heuristic approach based upon the length scales of the dominant physical mechanism present in such devices.