Abstract

Photochromic materials are attractive for the development of holograms for different reasons: they show a modulation of the complex refractive index, meaning they are suitable for both amplitude and phase holograms; they are self-developing materials, which do not require any chemical process after the light exposure to obtain the final hologram; the holograms are rewritable, making the system a convenient reconfigurable platform for these types of diffractive elements. In this paper, we will show the features of photochromic materials, in particular diarylethenes in terms of the modulation of a transparency and refractive index, which are mandatory for their use in holography. Moreover, we report on the strategies used to write binary and grayscale holograms and their achieved results. The outcomes are general, and they can be further applied to other classes of photochromic materials in order to optimize the system for achieving high efficiency and high fidelity holograms.

Highlights

  • The possibility of storing a 3D scene in a substrate has been a dream for a long time

  • By using polymer-dispersed liquid crystal combined with holography (H-PDLC), it is possible to obtain switchable phase gratings and other optical elements thanks to the phase separation that induces the refractive index modulation and the application of the electric field [30,31]

  • We report on the main features of photochromic diarylethenes in terms of relevant properties for phase and amplitude holograms

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Summary

Introduction

The possibility of storing a 3D scene in a substrate has been a dream for a long time. An ideal material for hologram manufacturing should show [4]: a high spatial resolution, a large dynamic range, a good signal to noise ratio, high optical quality, and large sensitivity in a wide spectral range Another attractive property that holographic materials may show is the ability to self-develop, namely, no chemical process is required after the pattern transfer to obtain the final usable hologram. There are different approaches to achieve these kinds of diffractive devices and photochromic dyes surely are an interesting option Nice features of such materials include their rewritability, which is intrinsic in the reversible transformation. By using polymer-dispersed liquid crystal combined with holography (H-PDLC), it is possible to obtain switchable phase gratings and other optical elements thanks to the phase separation that induces the refractive index modulation and the application of the electric field [30,31]. The results here reported can be generalized to other classes of photochromic materials and could inspire the development of new/optimized photochromic systems for high efficiency and high fidelity holographic optical elements

Computer-Generated Holograms
Fourier and Fresnel CGHs
Diffraction Efficiency
Diarylethenes
UV-vis
Series
Computational
Selection
Parameters
Results
Refractive Index Modulation
Writing Strategies and Examples of CGHs
Mask Projection
Direct Laser Writing
Examples
Conclusions
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