The present work showcases an innovative optimization methodology based on deep learning that combines Multi- Valued Artificial Neural Networks and back-propagation optimization. The methodology addresses the inherent limitations of conventional approaches when employed in isolation. We applied the proposed methodology to design structural color filters that surpasses the sRGB gamut while preserving fabrication constraints.
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.
Liquid Crystals are birefringent materials, which address many applications such as visualization with Liquid Crystal Display (LCD) or beam shaping with Liquid Crystal on Silicon devices (LCoS). Recently, several research teams proposed using liquid crystals in photonics devices applied to new kinds of projection displays. Augmented Reality (AR) is one of the domains, which could benefit from these developments, thanks to the necessity to create active and transparent optical function. In this contribution, we present recent works at CEA Leti to develop a switchable photonic extraction grating adapted to a specific near-eye device. Two different technics are detailed and studied with FDTD simulations. We also show first experimental characterization of an impregnated diffraction grating used in a free space optical set-up
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