3D-nanoprinted vertical coupler using hybrid lithography for optical redistribution applications

We demonstrate a polymeric vertical coupler for optical redistribution applications. The device is fabricated using a hybrid-lithography process, combining ultraviolet (UV) lithography for a planar optical redistribution layer (ORDL) with two-photon polymerization (TPP) for the vertical coupling micromirrors. By leveraging the high refractive-index contrast between the core and cladding, we realized an all-solid total internal reflection (TIR) mirror, eliminating the need for complex metallization or air cavities. To ensure manufacturability, we incorporated a support structure into the coupler design. Theoretical study predicts coupling efficiencies of 89.4% and 81.6% for the unsupported and supported structures, respectively. Experimental characterization of the fabricated device demonstrates a coupling loss of approximately 3.3 dB at a telecommunication wavelength of 1310 nm. This work provides a scalable and cost-effective approach for integrating high-performance vertical interconnects into 3D photonic systems.