Information-optimized color metalenses for camera imaging

Abstract

A metalens is conventionally built by prescribing a target phase and matching each meta-atom to it, and making that phase achromatic across the visible band is the main difficulty in color imaging. We remove the prescribed phase entirely. The meta-atom width map is optimized directly against the information the raw, noisy, mosaic-sampled camera measurement carries about the target image, differentiated through Maxwell propagation, the color-filter mosaic, pixel integration and sensor noise, with material, thickness and library held fixed. On a single-layer silicon-nitride platform, starting from a hyperbolic design, this raises delivered target information by 15.8% despite lower collected charge, produces the most balanced set of channel responses at the sensor plane relative to their respective axial maxima, and reduces blue-channel blur. A high-signal-to-noise held-out reconstruction improves in spatial fidelity and color accuracy. The same width-only optimization improves color across silicon-nitride, silicon-dioxide and titanium-dioxide libraries.

50 pages, 14 figures