McLeod Robert R
Electrical Computer and Energy Engineering Department and Materials Science and Engineering Program, UCB 425, University of Colorado Boulder, Boulder, CO 80309, USA.
Polymers (Basel). 2020 Nov 19;12(11):2744. doi: 10.3390/polym12112744.
Although the angular distribution of noise gratings in holographic photopolymer is understood to arise from Bragg matching, the details of scatter strength and dynamics are not fully understood. This confounds development of materials and recording techniques that minimize haze. Here, the kinetics are studied using a multi-physics numerical approach coupling diffraction of light from the dynamic material including scatter centers, reactions of chemical species initiated by this light, diffusion and swelling of these constituents, and the formation of the refractive index from the resulting composition. The approach is validated in the case of two-beam transmission holography by comparison to traditional harmonic series and rigorous coupled-mode approaches. Two beam holography in the presence of scatter is then used to study haze development. This reveals that haze due to weak noise gratings grows significantly above initial scatter only in reaction-limited materials, consistent with proposed Bragg-matched amplification mechanisms. Amplified haze is found to be proportional to initial scatter, quantifying the impact of clean sample fabrication. Conversely, haze is found to grow super-linearly with sample thickness, illustrating the significant challenge for applications requiring low haze in large thickness.
尽管全息光聚合物中噪声光栅的角分布被认为是由布拉格匹配引起的，但散射强度和动力学的细节尚未完全理解。这给开发使雾度最小化的材料和记录技术带来了困扰。在此，使用多物理场数值方法研究动力学，该方法耦合了来自动态材料（包括散射中心）的光衍射、由此光引发的化学物种反应、这些成分的扩散和膨胀以及由所得成分形成的折射率。通过与传统谐波级数和严格耦合模方法进行比较，该方法在双光束透射全息术的情况下得到了验证。然后利用存在散射时的双光束全息术来研究雾度的发展。这表明，仅在反应受限的材料中，由弱噪声光栅引起的雾度在初始散射之上会显著增加，这与所提出的布拉格匹配放大机制一致。发现放大后的雾度与初始散射成正比，从而量化了清洁样品制造的影响。相反，发现雾度随样品厚度超线性增长，这说明了对于需要大厚度低雾度的应用所面临的重大挑战。
