ANALYSIS OF CLADDED UNIAXIAL SINGLE-CRYSTAL FIBERS

A complete analysis for a uniaxial core-uniaxial cladding step-index fiber is presented. Numerical results of a few lowest-order modes are presented for weakly guiding LiNbO3 single-crystal cladded fibers. We find that the fundamental mode in a uniaxial fiber is not linearly polarized but has significant orthogonal components, even though the fiber is under weak guidance and has no modal birefringence because the wave propagation direction is the crystalline Z axis. We conclude that large anisotropy can cause the relatively large minor field in a uniaxial fiber, but modal birefringence is not necessarily involved. The electrical lines of the fundamental mode for a uniaxial fiber are also considerably different from those of an isotropic one, but eigenvalues and fractions of power in the core are similar.