Film‐Based Multi‐Photon Lithography for Efficient Printing of Electromagnetic Surface Structures

Abstract This study introduces an approach, termed film‐based multi‐photon lithography (MPL), for the efficient fabrication of electromagnetic surface structures. Unlike conventional MPL, which utilizes droplet‐shaped photosensitive volumes for the fabrication of 3D structures, this method employs photosensitive thin films to minimize the influence of axial voxel dimensions. This modification enables rapid printing of 2D surface structures over large areas with dry objective lenses, achieving feature sizes as small as 250 nm. The versatility of film‐based MPL is demonstrated through the fabrication of terahertz metasurfaces featuring metallized split‐ring resonators on glass substrates, as well as mid‐infrared metasurfaces comprising dielectric pillars on silicon‐on‐insulator substrates. These structures are successfully produced over areas spanning cm² and mm² using a hybrid organic–inorganic photoresist within a maximum processing time of 2 h. Particularly with hybrid organic‐inorganic photoresists, additional post‐processing via calcination shows significant potential for producing purely inorganic periodic structures with reduced feature sizes. Moreover, film‐based MPL enables the fabrication of high‐resolution 2.5D surface structures, which are challenging to achieve using conventional lithographic methods. Experimental results are analyzed through profilometry, scanning electron microscopy, Fourier transform infrared spectroscopy, and energy‐ dispersive X‐ray spectroscopy, while simulations confirmed the electromagnetic responses of the metasurfaces.