Metastructures-Induced Hyper-Resolution in Two-Photon Direct Laser Writing

Two-photon direct laser writing (TP-DLW) is widely used in stereolithographic processes for realizing sophisticated micro- and nanoscale structures with application in fluidics, photonics, and biomedical devices. In this chapter, it is detailed how leveraging on metal-dielectric metastructures with peculiar optical functionalities is possible to enhance the performance of a generic TP-DLW device, thus enabling the fabrication of all-dielectric nanostructures with hyper-resolution in height ($15\:nm$) and width as small as $150\:nm$. The results open new frontiers toward the realization of all-dielectric ultraflat optical elements in a noticeably shorter time than standard time-consuming electron and deep-UV lithography processes.