Modular expanded beam interface for cross-platform optical integration enabled by 3D-printed micro-optics

A versatile packaging concept using collimated out-of-plane beams as a common optical interface between components like photonic integrated circuits (PICs), laser diodes (LDs), polymer waveguides and optical fibers is presented. Therefore, each component is integrated on a substrate together with micro-optical elements such as mirrors and lenses, which emit/receive collimated expanded beams out-of-plane, enabling low-loss, alignment-tolerant coupling. Two C-band configurations demonstrate the approach: (1) coupling a single-mode fiber (SMF) to a collimated circular beam out-of-plane with a mode field diameter (MFD) of 40 μm using an off-axis parabolic (OAP) mirror, and (2) coupling the elliptical beam emitted by an indium phosphide LD to the same out-of-plane 40 μm beam using an OAP mirror. The micro-optics were fabricated using two-photon polymerization and validated experimentally, demonstrating the feasibility of this modular coupling approach.