One-step Patterning of Sub-wavelength Plasmonic Gratings in Metal-Polymer Composites

2D and 3D micro/nano fabrication based on two-photon polymerization (TPP) has emerged as a strong contender for additive manufacturing for wide variety of applications. In this manuscript we report one step patterning of structurally stable, subwavelength 2D and 3D gold nanostructures using femto-second laser by incorporating single photon photoinitiator only in pure and metal precursor doped polymers. The metal polymer composite nanostructures are written directly by in-situ reduction of gold precursor within the photoresist using femto-second laser irradiation. The photo-initiator triggers the reduction of gold precursor and induces simultaneous polymerization of the photoresist based on two-photon absorption phenomenon. Diffraction gratings with varied loading of gold precursors in photoresist have been fabricated and characterized by measuring their diffraction efficiencies in the infrared region. Minimum line width of 390 nm has been achieved for 5 wt% gold loaded polymers. Systematic studies of the effect of laser power, metal precursor loading etc. on the line-widths have also been performed. These investigations are expected to pave way for exploration of new material combinations for development of simple fabrication for fabrication of metal composite functional structures at significantly low cost and with high-throughput.