Two-photon lithography of subwavelength plasmonic microstructures in metal-polymer composite resin

Abstract

Two-photon lithography has emerged as a tool of prime importance for additive manufacturing of 2D and 3D micro/nanostructures in metal-polymer composite resins with resolutions beyond the diffraction limit. Two-photon absorption dyes used are not only expensive, difficult to synthesize but also proprietary. To mitigate these challenges, we report formulation of two-photon polymerizable metal doped resin. Two-photon polymerization and reduction of metal-polymer composite resins is used for fabricating plasmonic micro/nanostructures. Simultaneous photopolymerization and photoreduction restricts the diffusion of the photoreduced metal-ions from the metal doped polymeric voxel, resulting in metal doped precisely fabricated micro/nanostructures. The impact of gold loading in the composite resin and fabrication process parameters on resolution of fabricated structureswere systematically studied. Minimum linewidth of ~350 nm using an 800 nm laser excitation was achieved for 10 wt% metal loaded polymer. A two-dimensional plasmonic mesh structure have been fabricated over millimetre scale, and structural colouration is demonstrated. This technique holds great potential to initiate new developments in additive manufacturing of metal-dielectric composite structures and expected to create a paradigm shift in areas such as metaphotonics and plasmonic metamaterials, among others.