Topological charge dependence of speckle correlation and probability density function

Abstract

In this paper, we investigate the correlation and probability density function of the speckle field produced by illuminating Laguerre-Gaussian (LG) beams onto a ground glass. The LG beams, with different topological charges ℓ, are generated using a spatial light modulator (SLM) and transmitted to the ground glass. The ground glass is rotated from θ₀ = 0° to 1.0° in increments of 0.01° using a computer-controlled rotational stage. Results show that optical memory, based on correlation, decreases as ℓ increases. This is attributed to the increasing phase factor of the LG beams, which contributes to greater randomness in the speckle field. Moreover, we observe that speckles for all topological charges ℓ are not fully developed, as they do not follow the negative exponential distribution. Due to the decrease in the amplitude of the electric field, the peaks of the distribution decrease as ℓ increases. These findings may be of interest for a range of applications that rely on the statistical properties of speckle.