In order to improve the accuracy and efficiency of the thermal stress analysis of the planar optical waveguide by the finite element method

an improved plane strain model is presented. In this improved plane strain model

the thermal expansion coefficient of materials is described in orthogonal anisotropic way

and the material’s thermal expansion coefficient in the direction perpendicular to the propagation of the waveguide remains the actual material’s thermal expansion coefficient. However

the thermal expansion coefficient of material along the direction of propagation of the waveguide is changed appropriately to maintain deformation coordination. With the modified material model

the thermal stress of the planar optical waveguide is calculated by the ordinary plane strain model. The calculation results show that the maximum error of the stress obtained by the improved plane strain model is only 0.4% compared with the generalized plane strain model

and the calculation time is reduced to 12.6% of the generalized plane strain model. Compared with the ordinary plane strain model

the calculation precision of the improved plane strain model is greatly improved with almost same calculation time.