CHARACTERISTIC MODES AND SCATTERING LOSS OF ASYMMETRIC SLAB OPTICAL WAVEGUIDES.

In an asymmetric optical waveguide the scattering loss is large compared to a symmetric one. An analytical method is described which derives proper modes and scattering loss in a waveguide with an arbitrary refractive index profile. An asymmetry factor A//s is defined and its relation to the scattering loss is obtained. When two interfaces have different ratios of refractive indexes across them, the cutoff film thickness for the fundamental mode is proportional to (A//s)** one-half in a restricted region and the scattering loss to (A//s plus 1). For cases where the refractive index varies slowly near the interface the properties of a thin-film waveguide are determined to a good approximation.