White noise analysis of a speckle field with optical memory effect

Abstract

In this paper, we introduce white noise analysis to study the optical memory effect of a speckle field. We generate a speckle pattern by shining laser pointer on ground glass as a scattering medium. By tilting the ground glass from 0° to 1° with 0.01° increments, we observe a short-range correlation between speckle patterns, indicating the presence of an optical memory in the speckle field. Furthermore, we extract the intensity at the center of the speckle pattern at different tilting angles and analyze the fluctuations of its values by determining the mean square displacement (MSD). The mean square displacement (MSD) dictates the type of memory function present in the field. To determine this, we fit our experimental MSD with the theoretical MSD available in the literature. Our results indicate that the optical memory effect attributed to the speckle field corresponds to fractional Brownian motion, with an average Hurst parameter of 0.657 ± 0.024. This experimental value suggests that the diffusivity of the intensity is superdiffusive and positively correlated.