Abstract
In this work, the theoretical model of non-uniform diffraction structures’ holographic formation in liquid crystal-photopolymer (LC-PPM) composite materials with a dye-sensitizer is developed. The model takes into account the arbitrary character of amplitude and phase spatial distributions of recording light field, its arbitrary polarization state and also a non-linearity of the recording process. Two the most common types of liquid crystal-photopolymer composite are investigated: Holographic polymer-dispersed liquid crystals (H-PDLC) and polymer-stabilized liquid crystals (PSLC). Numerical simulations for the most common cases of holographic formation schemes are made. It is shown that due to the photo-induced Freedericksz transition, in the case of arbitrary polarization states of recording light beams, the non-uniform polarization diffraction grating (PDG) is formed in LC-PPM. Numerical simulations’ results show that PDG’s contribution to the change of the dielectric tensor of the media is comparable with the contribution of the photopolymerization-diffusion process.
Highlights
Diffraction structures holographically formed in composite photopolymer materials are well known since 1960s–1970s [1,2,3]
To estimate the contribution of the photo-polymerization-diffusion mechanism to the formation of a non-uniform holographic diffraction structure (HDS) by arbitrarily polarized waves, it is sufficient to calculate the amplitudes of the harmonics with varying bm (r, τ)
It can be seen that recording by two waves with orthogonal circular polarization leads to the formation of polarization grating with a more pronounced harmonic character compared to the structure recorded with linear orthogonal polarized waves, since in this case there is no modulation of ellipticity
Summary
Diffraction structures holographically formed in composite photopolymer materials (containing monomer, dye, initiator, plasticizer, etc.) are well known since 1960s–1970s [1,2,3]. Some theoretical models of HDS formation in photopolymerizable compositions [22,23,24,25,26,27,28], including photopolymer-liquid crystals ones [29,30,31], are developed by the present time. When designing a complicated holographic device (for example AR display) based on anisotropic liquid crystal-photopolymer composite materials, containing slanted transparent, and/or reflection gratings, the developer must consider the contributions of all of the influencing recording nonlinear processes: Photopolymerization, diffusion, and polarization grating formation. The purposes of the present work are: to develop a theoretical model, taking into account all of the described effects; to numerically investigate the value of PDG’s contribution to the change of the dielectric tensor of the media
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