A 3-D planar microlens for an effective monolithic optical interconnection system

A three-dimensional (3-D) planar microlens with curved sidewalls was fabricated by using the recently developed 3-D diffuser lithography and the polydimethylsiloxane (PDMS) replication method. The sidewall of the fabricated 3-D planar microlens had a radius of curvature of 140 μm, and a well-defined focal spot with a width of 1.5 μm and a height of 3 μm was observed. An excellent single-mode fiber-to-fiber coupling efficiency of 71% was demonstrated by applying the developed 3-D planar microlens, which displayed more than two times the coupling ability compared to that of a conventional two-dimensional planar microlens with straight sidewalls. Finally, it was verified that the coupling efficiency was little affected by variation in the process conditions used for the photoresist mold fabrication.