Optical waveguides and methods thereof

A method of forming an optical waveguide structure, comprising:

• providing a first material layer having a first refractive index and comprising a polymer matrix, at least one monomer compatible with the polymer matrix, a procatalyst, and a cocatalyst, where the polymer matrix and at least one monomer have different refractive indices, the cocatalyst is suitable for converting the procatalyst to a latently active form upon exposure to actinic radiation, and the latently active form is convertible to an active form upon heating to a first temperature;
• selectively exposing a first portion of the first material layer to the actinic radiation;
• and
• first heating the first material layer to the first temperature, the first refractive index changing to a second refractive index.