Characterization of irradiance effects on curing of siloxane for embedded waveguide applications
In order to maintain the overall optical performance in a step index rectangular waveguide, the complex index of refraction of the core and cladding material must be maintained throughout the cycle of the lithographic fabrication process. The percentage of the core and cladding material that is cured and the irradiance that cure took place directly affects the complex index of refraction of these materials. Siloxanes produced by Dow Corning have been selected to meet the requirements for embedded waveguides for circuit board applications due to their optical performance characteristics and their compatibility with current manufacturing techniques. The required total dose for a 50 μm thick layer of siloxane is 1200 mJ at an irradiance of 30 mW/cm2. In order to utilize lower irradiance levels the total dose of the ultraviolet exposure must be characterized and calibrated. By measuring the changes in the absorption peaks of the materials using transmission data from ellipsometric techniques it is possible to define the percentage cure of the siloxane from different curing profiles. Ellipsometric techniques were also utilized to measure the complex refractive index of the materials cured using different profiles. It was found that the total dose required for a complete cure and the complex refractive index of these materials drastically changes with different irradiances and the profile for the total dose compared to the curing of the siloxane materials at all irradiances is logarithmic.
Proc. SPIE 7941, Integrated Optics: Devices, Materials, and Technologies XV, 794103
Daunais, T. M., Walczak, K. A., Middlebrook, C., & Bergstrom, P. L. (2011). Characterization of irradiance effects on curing of siloxane for embedded waveguide applications. Proc. SPIE 7941, Integrated Optics: Devices, Materials, and Technologies XV, 794103, (). http://dx.doi.org/https://doi.org/10.1117/12.877553