Printable Nanocomposite Metalens for High-Contrast Near-Infrared Imaging.

Printable metalenses composed of a silicon nanocomposite are developed to overcome the manufacturing limitations of conventional metalenses. The nanocomposite is synthesized by dispersing silicon nanoparticles in a thermally printable resin, which not only achieves a high refractive index for high-efficiency metalenses but also printing compatibility for inexpensive manufacturing of metalenses. The synthesized nanocomposite exhibits high refractive index >2.2 in the near-infrared regime, and only 10% uniform volume shrinkage after thermal annealing, so the nanocomposite is appropriate for elaborate nanofabrication compared to commercial high-index printable materials. A 4 mm-diameter metalens operating at the wavelength of 940 nm is fabricated using the nanocomposite and one-step printing without any secondary operations. The fabricated metalens verifies a high focusing efficiency of 47%, which can be further increased by optimizing the composition of the nanocomposite. The printing mold is reusable, so the large-scale metalenses can be printed rapidly and repeatedly. A compact near-infrared camera combined with the nanocomposite metalens is also demonstrated, and an image of the veins underneath human skin is captured to confirm the applicability of the nanocomposite metalens for biomedical imaging.