Research On Holographic Volume Recording In Nanoparticle-doped Photopolymers

Nanocomposites photonic materials are being actively studied for practical applications such as touch screen,wearable devices,optical sensors,photolithography,and neutron optics.For many of these applications,it is essential to fabricate embedded phase structures into media,in order to implement various properties for its practicality.High-contrast refractive-index changes??n?with promising flexibility are usually desired for these applications.Photopolymers as an appealing candidate are attractive because they hold several advantages,such as low cost,ease of use,shape flexibility,large-area process ability,and self-development capability.Such materials are also able to tailored to meet the needs of a specific application through optical and chemical approaches.Among various types of photopolymer materials photopolymerizable organic-inorganic nanocomposites,have thus far shown their excellent performance in holographic data storage,nonlinear optics and neutron optics.This is so because it provides large refractive index change??n?,mitigated shrinkage and high thermal stability.This thesis focuses on the influence on the optical and mechanical properties of materials through the doping of nanoparticles to fabricate high performance flexible nanocomposites for holographic diffraction element recording.The main research contents of the thesis are as follows:In many new photopolymer materials,polymers using thiol-ene monomers are widely concerned in the field of holography.The basic principles of holographic recording in photopolymers are deeply studied,and the diffusion kinetics of photopolymers doped with nanoparticles are described in details.The main performance parameters of photopolymers are introduced.A semi-automatic controlling system for holographic recordings was designed.In order to monitor the grating formation process in real time,a program was engineered to control the optical path and collect data.Combining the advantages of both thiol-ene and thiol-acrylate monomer blends,a set of examinations on nanoparticle-doped photopolymers with good flexibility and diffraction efficiency are carried out.Firstly,the grating performance of SiO₂nanoparticles doped acrylate-thiol-ene monomer blend is studied.The optimum exposure intensity and doping concentration of SiO₂ nanoparticles are obtained.As the concentration of SiO₂ nanoparticles increasing,the diffraction efficiency of the grating increases.When the concentration of SiO₂ nanoparticles reaches 10 wt%,the diffraction efficiency increases as large as 34%.Excess SiO₂ leads to a decrease in?n may be attributed to the increased viscosity of the matrix by SiO₂,that leads to lower the diffusion of monomer and nanoparticles.Secondly,in order to further increase the diffraction efficiency,BzO₂ and single-walled carbon nanotubes are used.The co-initiator BzO₂ causes an increase in the concentration of the radicals,and thereby increasing the monomer conversion rate.By doping BzO₂,the diffraction efficiency of the grating is increased to 64%while the optimum recording intensity was reduced to 0.25 mW/cm².The sample doped with single-walled carbon nanotubes?SWCNTs?was then examined.When the SWCNT doping concentration was 0.0015 wt%,the refractive index modulation of the grating reaches a maximum value of 2.80×10^-3,and the diffraction efficiency achieved more than 95%.Finally,the sensitivity,morphology,absorption spectrum and extinction spectrum of the sample are characterized.The experimental results indicate the excellent optical properties of the proposed SWCNT doped photopolymer.In addition,the inclusion of single-walled carbon nanotubes does not only enhance the optical properties of the material,but also improve the mechanical properties of the proposed material.The hardness and Young's modulus of the material are measured by using a nanoindenter.The experimental results show that by doping single-walled carbon nanotubes,the hardness of the material is increased by a factor of 4 with less variation in its Young's modulus.In this thesis,the effects of inclusion of various nanoparticles in photopolymers are studied,and flexible films with high diffraction efficiency,high refractive index modulation and high sensitivity are fabricated.Because of the advantages of the proposed SWCNT doped photopolymer performs,it is expected to have potential capacity for the application of display and optical sensor.