Dual focus wavefront tilting silicon nitride-based metalenses manufactured using deep-ultraviolet scanner lithography

We present a dual focus wavefront tilting metalens, a lens of a few micrometers thick that compensates for incidence angles of ±5° and focuses them to the same target. The metalens comprises an array of Si₃N₄ nanopillars. We manufactured the metalens using 193 nm deep-ultraviolet scanner lithography, suitable for high-volume manufacturing. Using this metalens, we demonstrate a proof-of-concept for chip-to-free-space coupling by directing light from one fibre collimator at +5° towards a mirror and recoupling this light into another fibre collimator at -5°. The metalens achieved a focusing efficiency of 9.4%. This efficiency has the potential to be improved to 64%. The metalens can be integrated into photonic circuits for enhanced coupling with distant objects. This work paves the way for further miniaturization of gas and metrology sensors.