Study and validation of switchable grating using liquid crystal for active waveguide addressing

In our Augmented Reality (AR) project, we are investigating the use of a retinal projection display based on the association of pixelated holograms and a dense distribution of waveguides. We study the use of gratings impregnated with liquid crystal to actively extract light from waveguides. We explore two extraction strategies: tuning the refractive index contrast between the grating teeth and grooves to erase the grating diffraction effect and changing the index of the waveguide cladding to tune the evanescence of the guided mode. Firstly, we present and discuss the measurements of the diffraction efficiency of nano-imprint gratings impregnated with liquid crystal and refractive liquid index. Secondly, we discuss the results of integrated switchable extraction grating of the second strategy.