Engineering of Large-Scale Plasmonic Networks for Collective Emission

The development and research on metamaterials opens the doors for futuristic technologies using their custom-designed properties to interact with and manipulate the flow of light. AR glasses, beam-steering antennas and enhanced solar powered systems seem to be in the palm of our hand. The effectiveness of such plasmonic parts depends vastly on the size of the interactive material and research is driving into the direction of fabricating larger connected and homogeneous surfaces of metamaterials, which allows exploitation for custom-designed thermal emission, and photo- and electro-luminescence.<br/>A promising approach for the nano-fabrication of these metamaterials is the well-established block co-polymer self-assembly, where the differently polarized ends of the polymer cause the polymer-solvent system to align in either spheres, lamellas or complex three-dimensional “gyroid” formations. We use various fabrication protocols and polymers to reach the requirements in thickness, surface area and the level of order necessary for bespoke collective emission properties. By using a new solvent evaporation annealing technique involving a high boiling-point additive, birefringent optical properties indicate large-scale reproducible homogeneous network areas beyond previously reported results. The polymer in use is PI-PS-PEO (polyisoprene-<i>b</i>-polystyrene-<i>b</i>-poly(ethylene oxide)), which results in a 3D gyroid network morphology with a unit cell size of approximately 50 nm. Replicating these structures into different metals results in high quality polarizing optical metamaterials with large single crystal domains on the order of 0.5 mm², suitable to be used for polarized fluorescence and sensing applications.<br/>Concurrently, heated plasmonic materials can produce a strongly directional and therefore coherent thermal emission signal. This far-field thermal coherence, which seems to go against conventional wisdom, has been demonstrated in 2002 using phonon polaritons in a SiC grating with a period of about 6.25 μm, which is more than 100x larger than the period of the self-assembled structures.<br/>Here we show different approaches to fabricate and characterize chiral micrometer-scale ordered metamaterials made of platinum, whose thermal emission yields circular polarized light in the near-IR regime.