Review of Organic Photorefractive Materials and Their Use for Updateable 3D Display

Abstract

Photorefractive materials are capable of reversibly changing their index of refraction upon illumination. That property allows them to dynamically record holograms, which is a key function for developing an updateable holographic 3D display. The transition from inorganic photorefractive crystals to organic polymers meant that large display screens could be made. However, one essential figure of merit that needed to be worked out first was the sensitivity of the material that enables to record bright images in a short amount of time. In this review article, we describe how polymer engineering was able to overcome the problem of the material sensitivity. We highlight the importance of understanding the energy levels of the different species in order to optimize the efficiency and recording speed. We then discuss different photorefractive compounds and the reason for their particular figures of merit. Finally, we consider the technical choices taken to obtain an updateable 3D display using photorefractive polymer. By leveraging the unique properties of this holographic recording material, full color holograms were demonstrated, as well as refreshing rate of 100 hogels/second.

Improvements in VPHGs for astronomy based on photopolymers

“…For such reasons, a smaller and smaller employment of DCGs is expected in the future. Photorefractive materials 26,27 show a modulation not so large that limits their applications in dispersing element. Chalcogenide glasses 28 are interesting, but the application in large size element is not easy.…”

Laser ultrasonics for measurement of the thickness of metal plates using a photorefractive liquid crystal

“…Thus, it can be used as a sensor for the phase change of light. In addition to inorganic crystals such as lithium niobate and barium titanate, organic photoconductive polymers are known to exhibit the photorefractive effect [12][13][14]. However the response time is tens to hundreds of milliseconds, and large voltages of typically 5~7 kV in a 100 µm thick film must be applied to obtain a sufficient response.…”

Azo-carbazole copolymer-based composite films with high optical transparency for updatable holograms

“…Typical materials for updatable holograms include azobenzene molecules in a polymer matrix, [7][8][9] liquid crystals, 10,11 polymer liquid crystals, [12][13][14][15][16] and photorefractive polymers. [17][18][19][20] In particular, azobenzene molecules are the most promising candidates for updatable holography because they are well known as photosensitive chromophores that undergo trans-cis photoisomerization upon irradiation with light of an appropriate wavelength in solution or a host matrix. [21][22][23][24][25] When such photoisomerization is repeated in the host matrix, the long axis of the azobenzene chromophore aligns perpendicularly to the electric field vector of linearly polarized light, eventually inducing anisotropy.…”