Abstract: Elastic multilayer theory and stress concentration in buried channel waveguides are combined to obtain analytical solutions for thermal stress in the core of silica-on-silicon waveguides.Then the closed-form expression of stress anisotropy is obtained.It is shown that the anisotropy of thermal stress in conventional AWG comes from the initial warp and the thermal-expansion mismatch between waveguide layers.A complete analysis shows that the stress anisotropy can be minimized by tuning one of four parameters,including the thermal expansion coefficients of the substrate and upper cladding,and the thicknesses of the substrate and lower cladding,or by attaching a metal plate with proper thickness on the bottom of the arrayed waveguide.

Key words: optical waveguide, thermal stress, elastic multilayer system, stress concentration, stress plate