One-step hybrid 3D lithography for waveguide fabrication

Light coupling for integrated photonics is an ongoing research topic and especially important for out-of-plane coupling for batch testing and hybrid integration. In particular, achieving low losses in the visible range remains a challenge. Adding micro-optical elements after processing the waveguides is a viable solution. However, the post-process step requires precise and costly alignment procedures. In this talk, we present a one-step method based on two-photon polymerization direct laser writing where both refractive optical elements and silicon nitride waveguides are fabricated concurrently. We demonstrate devices with system losses of -6.8 dB at 532 nm and 3 dB bandwidth of 270 nm centered at 748 nm. We show that by adjusting the lens radius spectral tuning is possible. Simulations indicate a 93% field confinement that is virtually independent on the hybrid waveguide width, ensuring fabrication robustness and stability.