Stress effects on the performance of optical waveguides

Stresses can cause anisotropic and inhomogeneous distribution of the refractive index. Their effects on the performance of optical waveguides have been observed in photoelectric devices. In this paper, the photo-elastic relation and wave equations for inhomogeneous and anisotropic waveguides are reviewed. The effective refractive indexes and mode shapes of planar waveguides under different stress states are obtained analytically. It is found that stress can affect the optical performance; different stress states play different roles: high stress value can change the cutoff thickness, which may induce multimode; in-plane stress causes birefringence, which may induce polarization shift and polarization dependent loss; stress concentration can change the mode shape, which may induced large transition loss; and pure shear stress has little effects on the effective refractive index.