Leveraging on ENZ Metamaterials to Achieve 2D and 3D Hyper-Resolution in Two-Photon Direct Laser Writing.

A novel technique is developed to improve the resolution of two-photon direct laser writing lithography. Thanks to the high collimation enabled by extraordinary εNZ (near-zero) metamaterial features, ultrathin dielectric hyper-resolute nanostructures are within reach. With respect to the standard direct laser writing approach, a size reduction of 89% and 50%, in height and width respectively, is achieved with the height of the structures adjustable between 5 and 50 nm. The retrieved 2D fabrication parameters are exploited for realizing extremely thin all-dielectric metalenses tailored through deep machine learning codes. The hyper-resolution achieved in the writing process enables the fabrication of a highly detailed dielectric 3D bas-relief (with full height of 500 nm) of Da Vinci's "Lady with an Ermine". The proof-of-concept results show intriguing cues for the current and trendsetting research scenario in anti-counterfeiting applications and ultracompact photonics, paving the way for the realization of all-dielectric and apochromatic ultrathin imaging systems.