Stress-induced birefringence control in optical planar waveguides.

For what is to our knowledge the first time, the thermal-stress formula in analytical form is derived for the core layer in an optical planar waveguide by the thin-film approximation, which is based on a closed-form solution in multilayered isotropic structures off the edges. This formula indicates that elastic, thermal, and structural parameters can affect the magnitude of the stress. Using the formula, one can remove thermal stress and hence stress-induced birefringence by proper waveguide design.