Simultaneous fabrication of optical channel waveguides and out-of-plane branching mirrors from a polymeric slab structure

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Abstract
Recently, polymeric multimode optical waveguides have been widely studied for low-cost interconnection use. We describe fabrication processes for a low-loss poly(methyl methacrylate) (less than 0.1 dB/cm at 675 nm) waveguide based on the reactive-ion-etching technique and for a slope (45° mirror face) formed on the waveguide. To obtain a ridge core with a crack-free and extremely smooth surface, we applied a heating process at a temperature greater than the glass transition point and a smoothening process by solvent. Furthermore, to fabricate simultaneously both vertical and sloped sidewalls, we applied a unique phenomenon in the process that decreases the etching rate directly under a narrow opening of etching mask. By using the above fabrication techniques, we demonstrated an out-of-plane branching mirror.