Metallic helices have been extensively researched and demonstrated for their application as broadband circular polarizers in different frequency regimes. For making such 3D helices, two photon lithography (TPL) has been employed in conjunction with electroplating of metals. Recently, our group has demonstrated selective silver electroless plating of two photon fabricated polymer (SU-8) structures on silicon substrate. This procedure allows us to make metal-coated polymer helices. In this work, we examine how these fabrication process parameters could be tailored to obtain higher extinction ratios for circular polarizers in THz regime (or MIR regime). We further analyze the role of aspect-ratio of helices in their polarizing action. We will present both simulation and experimental results to show the improved performance of the polarizers.
Three dimensional metamaterials are fabricated using direct laser writing in SU-8 polymer followed by an electroless
coating process. A method has been developed to allow for selective electroless plating of SU-8 microstructures
with a smooth conformal coating of Ag. The process utilizes radio frequency plasma pretreatment
to modify the SU-8 surface so that Ag ions can nucleate on the surface, leaving the substrate uncoated. An array
of split ring resonators and other 3D microstructures are used to demonstrate how the technique can be applied
to metamaterials applications.