Vertical Optical Coupling Structure Based on Polymer for Small Size and High-Speed Photodetectors

This letter presents a new collective and passive thin-film 3D vertical optical coupling structure, which is fabricated based on SU-8 polymer. This technology compensates for the alignment errors of the present passive optical coupling solutions. The structure is collectively manufactured on a matrix of small-sized photodiodes on wafer level to vertically couple with a single-mode optical fiber. The proposed structure shows a coupling efficiency between the 10-μm active area diameter photodetector and single-mode fiber of 94% and a 1-dB alignment tolerance of ±9 μm at 1550 nm. Its wafer-level mass-production capability and manufacturing process simplicity make this novel coupling approach a potential solution for short- and long-range optical communication applications.