Advanced materials and methods for non-pixellated, complex modulation of light in computergenerated holography
Computer holography is the most promising technique in relation to virtual and augmented reality headlamps, because of the possibility of far-reaching miniaturization of the optical system by integrating multiple optical functions into one flat hologram generated and refreshed by a computer. Real-time computer-computed holograms (using GPU graphics processing) are displayed on a liquid crystal spatial light modulator (SLM). SLM illuminated by a continuous or pulsed laser beam recreates to the eye a three-dimensional scene encoded in a hologram with high fidelity. The devices based on computer holography displayed on SLM, previously demonstrated by the Contractors, showed significant advantages compared to the classic imaging approach. These include true threedimensional natural viewing to the human eye-brain system, wide dynamic range of display brightness, wide color reproduction, and low weight and volume of the display. Unfortunately, the fundamental limitations of liquid crystal SLM modulators are currently the main barrier to the development of computer holography. The biggest problems with SLMs are the regular matrix of pixels in which the light is modulated and the fact that SLM panels operate in reflection mode, which complicates the optical systems significantly. On the other hand, the regular SLM pixel matrix causes duplicates of the displayed images, which, overlapping the actual image, cause significant problems with the readability of the displayed content for the user.
Therefore, the aim of this Project is to continue research into alternative materials and methods of modulating light for the needs of computer holography of the future. Specifically, the project will involve two types of materials. The first is a magnetic material (i.e. cobalt-doped yttrium-iron garnet, YIG:Co and GdFeCo), showing an opto-magnetic (also photo-magnetic ) effect of magnetization recording using ultrashort polarized laser pulses. The unique advantage of this material is memory, transparency for visible light and ultra-fast switching with a very low energy cost. The second material is a mixture of liquid crystal (5CB, 6CHBT) with gold nanoparticles, which has been shown  to relocate nanoparticles under the influence of light pulses causing temporary formation of isotropic domains. The aim of the project is to investigate the possibility of using dynamically addressed structures of both types mentioned above for the purposes of phase and amplitude-phase light modulation in computer holography. For this purpose, two experiments will be carried out: point-by-point recording and holographic reproduction of diffraction patterns in an photo-magnetic sample in cooperation with the University of Bialystok, and precise measurement of liquid crystal samples previously exposed with dispersions of addressing light with smoothly changing density in the digital holography system (interferometric) write.
The analysis of the results of these experiments should allow the description of a new methodology of recording and reconstruction of holograms in advanced non-pixel light modulating media in prestigious journals.
“Excellence Initiative – Research University” POB Research Centre, Research Area Photonic Technologies, competition FOTECH-2
Warsaw University of Technology, Faculty of Physics
Warsaw University of Technology, Centre for Advanced Materials and Technologies CEZAMAT, University of Bialystok, Faculty of Physics
199 180 pln
Michał Makowski, PhD Eng.
Prof. Romuald B. Beck PhD, DSc, Eng. – on behalf of CEZAMAT