Color effects based on resonant waveguide grating embedded in a luminescent sol-gel layer

A subwavelength structure made of a resonant waveguide grating embedded in a luminescent sol-gel layer enables a dual color effect. The resonant waveguide grating consists of a diffraction grating and a high refractive index guiding layer using a TiO2 based sol-gel with a higher refractive index (n(g) = 2.2) than its silica sol-gel surroundings (n(s)=1.5). The resonant waveguide grating is designed to achieve visible resonant reflection of TE polarized incident waves in the green color spectrum. The resonant structure is then coated with a thick layer of silicone doped with a luminescent material of formulation Y2O2S:Eu3+. This latter leads to emission in the red domain under UV excitation. This quasi-symmetric structure is transparent in the visible range for observing the various phenomena. Nano-imprint technology is used for the fabrication of the grating on the sol gel layer to demonstrate its fabrication potential. Therefore, it is a low-cost fabrication technique used to replicate the microstructure, which can be up scaled for industrial applications. Preliminary results will be presented at the conference, covering modelling through the design of the optimized microstructures. Experimental results will be showcased with first demonstrators comprising Nanoimprinted sol-gel layers with a resonant waveguide grating and a luminescent layer. Experimental measurements will be carried out to characterise both the optical performance of the luminescent coating and the resonant waveguide grating.