Role of short-range order in manipulating light absorption in disordered media

摘要

Structural correlations have a significant effect on light propagation in disordered media. We numerically investigate the role of short-range order in light absorption in thin films with disordered nanoholes. Two types of disordered distributions, including stealthy hyperuniform (SHU) and hard disk (HD) patterns with different degrees of short-range order, are studied. We find that Bragg scattering induced by short-range order results in the appearance of a gradually sharper absorption peak with the increasing of degrees of short-range order (chi,phi). A physical model is proposed to calculate the in-plane angularly differential scattering cross section d sigma*/d theta of thin-film nanostructures with consideration of the structure factor S(q). Results reveal that a higher level of short-range order can enhance in-plane Bragg scattering in certain wavelengths and directions corresponding to rich and sharp peaks in the structure factor S(q), which can further modify morphology-dependent-like resonances of an individual scatterer and leads to a large improvement of absorptivity in thin films. Besides, the comparison results show that SHU structures exhibit better integrated absorption (IA) enhancement than both HD and periodic structures. And there is a transition of local-order phase between hexagonal lattices and square lattices for SHU structures, leading to an optimal absorption performance when chi is around 0.5 of interest. The present study paves the way to controlling light absorption and scattering using disordered nanostructures. (C) 2018 Optical Society of America