Laser Ablated Micromirrors for Printed Circuit Board Integrated Optical Interconnections

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Abstract
Optical interconnections offer a possible solution to the bandwidth problems associated with future electrical interconnections. Optics has proven its potential for long-haul communication networks, where it is today a well accepted standard. The integration towards shorter distances is challenging. Compatibility with technologies used in printed circuit board manufacturing is required to implement optical interconnections on board-level in the near future in a cost-effective way. Especially coupling structures, which are used to deflect the light beam over 90deg, pose problems. We propose the use of metallized 45deg micromirrors which are fabricated with the use of laser ablation. This letter gives an overview of the fabrication process and shows experimental results. The root-mean-square surface roughness of the mirror facet is 70 nm or better, depending on the used polymer material. The 45deg angle can be ablated with an accuracy of plusmn1 deg and has a high reproducibility. The mechanical properties of the micromirrors were maintained after a Telcordia 85/85 stability test