Methods, systems, and devices are disclosed for implementing athermal optical devices based on composite structures having different components with different thermal properties such as a composite structure having materials of positive and negative thermo-optic effects or a composite structure having materials exhibiting different thermal expansion coefficients. In one aspect, a method for providing thermally stabilized optical device structure against temperature fluctuations includes forming an optical device structure to include a first optical material and a second optical material different from the first optical material, in which one of the first and second optical material exhibits a positive thermal-optic effect and the other one exhibits a negative thermal-optic effect, and structuring the first and second optical materials in the optical device structure to reduce a change in an effective refractive index of the optical device structure collectively produced by the first and second optical materials in response to a temperature variation.