Exploring Metal-hydrogel-nanoisland structures as Reflective Color Filters

Abstract

Achieving dynamic color changes in response to environmental triggers, while preserving structural integrity, in conventional metal-insulator-metal filters remains a diffcult task in the field of active color filters and sensors. In this thesis, we fabricate lithography-free metal-hydrogel-nanoisland devices with controllable tunability in VIS-NIR range. By spatially varying the photo-polymerization time of the hydrogel layer in a single structure via selective UV exposure we study the effect of polymer cross-linkage on water swelling and hence device tunability. We optimize the coupling of the plasmon resonance of the top layer of these devices with that of the Fabry Perot cavity by sputtering metal ’nanoislands’ instead of only depositing a thin metallic film. The performance of these devices as nanoscale reflective color filters are explored with a combination of experimental reflectance measurements and numerical simulations. The work opens future research directions for contactless optical humidity sensors and scalable nanosized color filters with controllable tunability.