High-Efficiency Graphene Oxide Moiré Lenses Enabled by Cyclic Self-Assembly and Laser Nanoprinting

Abstract

Compact optical systems with continuously tunable focal lengths are highly desirable for machine vision, biomedical imaging, and miniaturized cameras. Rotational Moiré lenses offer a planar approach to focal-length tuning, but metasurface-based implementations typically require complex nanofabrication processes that complicate large-area production. Here, we present a cyclic, mask-free fabrication strategy that combines layer-by-layer self-assembly of two-dimensional graphene oxide (GO) and poly(diallyldimethylammonium chloride) (PDDA) with femtosecond laser nanoprinting. Repeated GO-PDDA assembly and spatially selective ablation enable atomic-scale thickness control and the construction of precise multilevel phase profiles, reducing phase-quantization errors and improving focusing efficiency. The measured focusing efficiencies of individual GO lenses increase from 22.4% for two phase levels to 54.8% for six levels. Using this six-level modulation strategy, the fabricated GO Moiré lens achieves continuous focal-length tuning from approximately 10 to 90 mm. Full-colour imaging with magnifications ranging from 1X to 9X is experimentally demonstrated. These results establish a cyclic, mask-free fabrication strategy for efficient multilevel GO flat optics and demonstrate its potential for compact, reconfigurable imaging.