Single-mode optical waveguide using siloxane polymer on Cu-polyimide substrate

A new single mode optical waveguide has been developed to obtain optoelectronic multichip modules. It is fabricated using siloxane polymer and thin film process technology onto a copper polyimide ceramic substrate. The siloxane polymer refractive index is 1.451, very similar to that of SiO₂. It is revealed that titanium doped siloxane polymer has refractive index of 1.4537 to 1.5949 (at 632.8 nm wavelength) which can be controlled by the TiO₂ content. The siloxane polymer which contains 2.0 wt% of TiO₂ has refractive index of 1.4437 at 1550 nm wavelength. Therefore, the siloxane polymer and the TiO₂ doped siloxane polymer can be used for cladding and core layers respectively, enabling a single mode waveguide. The core size is designed to be 4-8 μm wide by 7.0 μm thick to obtain a single mode optical waveguide at Δn=0.0022