Direct coupling of VCSELs to plastic optical fibers using guide holes patterned in a thick photoresist

We report a simple passive alignment method to couple plastic optical fibers (POFs) to vertical-cavity surface-emitting lasers (VCSELs) for use in parallel optical interconnects. Polymer guide holes were fabricated directly on the top of VCSELs by means of standard photolithography using SU-8 epoxy-based thick photoresist. Perfluorinated graded-index POFs were inserted and fixed in the guide holes to provide butt-coupled packaging modules. For a VCSEL of 15-μm diameter and a POF of 124-μm core diameter, coupling efficiencies were obtained between about 80% and 50%, depending on drive current. The standard deviation of the efficiency at a drive current of 10 mA was 5.9% for a 1 × 5 array.