Ultrathin flat optics allow control of light at the subwavelength scale that is unmatched by traditional refractive optics. To approach the atomically thin limit, the use of 2D materials is an attractive possibility due to their high refractive indices. However, achievement of diffraction-limited focusing and imaging is challenged by their thickness-limited spatial resolution and focusing efficiency. Here we report a universal method to transform 2D monolayers into ultrathin flat lenses. Femtosecond laser direct writing was applied to generate local scattering media inside a monolayer, which overcomes the longstanding challenge of obtaining sufficient phase or amplitude modulation in atomically thin 2D materials. We achieved highly efficient 3D focusing with subwavelength resolution and diffraction-limited imaging. The high focusing performance even allows diffraction-limited imaging at different focal positions with varying magnifications. Our work paves the way for downscaling of optical devices using 2D materials and reports an unprecedented approach for fabricating ultrathin imaging devices.

超薄平面光学器件可以在亚波长范围内控制光，这是传统折射光学器件无法比拟的。为了接近原子薄的极限，使用二维材料是一种有吸引力的可能性，因为它们具有高折射率。然而，衍射极限聚焦和成像的实现受到其厚度有限的空间分辨率和聚焦效率的挑战。在这里，我们报告了一种将 2D 单层转化为超薄平面透镜的通用方法。应用飞秒激光直写在单层内生成局部散射介质，克服了在原子薄的二维材料中获得足够的相位或幅度调制的长期挑战。我们通过亚波长分辨率和衍射极限成像实现了高效 3D 聚焦。高聚焦性能甚至允许在不同焦点位置以不同的放大倍率进行衍射极限成像。我们的工作为使用二维材料缩小光学设备的尺寸铺平了道路，并报告了一种前所未有的制造超薄成像设备的方法。