Nondestructive investigation on the nanocomposite ordering upon holography using Mueller matrix ellipsometry

Abstract

Ordered materials, which hold organized structures of heterogeneous matter and thus always present superior performance than their non-ordered counterparts, have been constantly pursued. Nevertheless, the direct, precise and nondestructive observation of the ordering process, which is especially critical for evaluating the quality of consecutive manufacturing, remains a formidable challenge. Herein, we introduce Mueller matrix ellipsometry (MME) as a nondestructive method to quantitatively investigate the nanocomposite ordering process upon holography. This nondestructive investigation directly offers the exact width of, refractive index and nanoparticle fraction in each bright (constructive) and dark (destructive) interference area, which is impossible to be implemented using other existing techniques. Interestingly, the width of dark regions in the formed holographic gratings is observed to decrease while the width of bright regions increases with an augmentation of holographic recording time, distinct from previous width-equal assumption. Meanwhile, an apparent diffusion coefficient of 2 × 10−15 m2 s−1 for nanoparticles is determined on the basis of time dependent grating parameter variation, which is 3 orders of magnitude lower than the initial value theoretically predicted by the Stokes-Einstein diffusion equation. The distinct diffusion coefficient is attributed to the rapid increase of viscosity driven by polymerization during holography. No depolarization is observed in these holographic polymer nanocomposites, indicating uniform dispersion of nanoparticles in the polymer matrices. The proposed protocol herein is envisioned to pave the way for precisely and nondestructively understanding the formation of ordered structure in electronics, photonics, photovoltaics, biomaterials and other disciplines.