Photonic wire bonding: Nanophotonic interconnects fabricated by direct-write 3D lithography

Photonic wire bonding enables single-mode connections between nanophotonic circuits that are located on different chips. The technique relies on three-dimensional (3D) freeform waveguides that are fabricated by two-photon polymerization of negative-tone resist materials in the focus of a high-NA pulsed femtosecond laser beam. The shape of the photonic wire bonds can be adjusted to the positions of the chips such that high-precision alignment becomes obsolete. This makes the technique particularly attractive for automated industrial fabrication of photonic multi-chip modules that combine the strengths of different optical integration platforms.