Optical Waveguide-to-photodiode Coupling Technique Using Total Internal Reflection Mirrors Fabricated In Polyimide Optical Waveguides

A novel optical coupling structure from waveguide to flip-chip bonded photodiode is presented by using a total internal reflection (TIR) mirror fabricated in a polyimide waveguide. The TIR mirror was made by using reactive ion etching (RIE) while tilting the substrate at an angle CL to the normal direction of the cathode. Reflection loss was less than 1.5 dB. This mirror can be used for high-efficiency coupling between the waveguide and a flip-chip bonded photodiode in high-speed opto-electronic multichip modules.