Printable grayscale nano-template for full-colour organic light-emitting diode near-eye displays with 3D achromatic metalenses.

Achromatic metalenses are essential for enabling compact, full-color imaging systems in augmented and virtual reality displays. Here, we present printable 3D achromatic metalenses using grayscale electron beam lithography (EBL) and dry etching-based height-encoded nano-template. By integrating nanoimprint lithography (NIL) from a nano-template without a soft mold, we realize high fidelity and throughput of 3D achromatic metalenses. The imprinted 3D meta-atoms provide controllable height diversity, introducing an additional degree of freedom for phase engineering even on a low-index resin platform. We design the metalens using a library-based phase-matching, where precomputed electromagnetic responses are used to select meta-atoms that best reproduce the hyperbolic phase simultaneously at RGB wavelengths. Our 3D achromatic metalens with a numerical aperture of 0.31 achieves diffraction-limited focusing at the same focal length across RGB wavelengths. The measured focusing efficiencies are 14.8%, 11.3%, and 12.3% at 450, 532, and 635 nm, respectively. As a proof of concept, we apply our 3D achromatic metalenses to a VR imaging platform, achieving a full-colour image. This work highlights grayscale EBL and NIL as a critical solution for achieving both aberration-free performance and scalable production, paving the way for next-generation compact and full-colour meta-optics.