Control of birefringence using polymer as cladding layer in optical planar waveguides

We demonstrate theoretically that a polymer layer, when used as cladding layer for silica-based planar optical waveguides on a silicon substrate, can substantially reduce birefringence. Multilayer planar optical waveguides usually exhibit stresses that are caused by thermal-induced strains that originate from the bonding of the layers, in addition to intrinsic strains. Effect of various intrinsic properties on thermal stress as a function of thickness of the guiding layer is studied. It is shown that it is possible to achieve the thermal stress free and, hence, the stress-induced birefringence free waveguide devices by proper waveguide designs.