Tunable dielectric metasurface upon using Nematic liquid crystals for color filter application

Abstract

In the realm of intensive research on metamaterials, particularly, the two-dimensional analogue, known as metasurfaces have attracted researchers due to their lower losses, high efficiencies and low cost as compared to plasmonic metasurfaces. Dielectric metasurfaces (DMs) have been widely reported to experience magnetic and electric dipole Mie type resonances, in which, upon tuning these two resonances, dielectric metasurfaces can exhibit spatially varying optical responses, phases and polarizations of scattered fields. Recently, dielectric metasurfaces have been used for color printing application with very high color vibrancy. However, the fundamental building blocks essential for the realization of optical metasurfaces are designed with uniform dimension nano structures, resonating at particular wave length, thus printing image only with particular color. In order to be able to cover the whole optical regime, the metasurface needs to be designed with tunable optical response to be able to print images with multiple colors. In this work, we report a cubic TiO₂ metasurface which experience magnetic and electric dipole resonances in the optical regime. We are able to tune the reflection peak of both resonances using Nematic liquid crystal (LCs). LCs are anisotropic materials with controlled orientation based upon different applied voltages. Changing the orientation of the LC allows for tuning the resultant of the electric field component of the LC and thus the reflection peak of the metasurface can be tuned across the optical regime. We report a tunable DM for optical filters application using single dimension designed metausrfcae with efficiency close to 99 % covering three colors in the visible range: red, orange and green.