Multiscale permutation entropy analysis of laser beam wandering in isotropic turbulence

GULICH, DAMIÁN; ROSSO, OSVALDO A.; ZUNINO, LUCIANO; PÉREZ, DARÍO G.; OLIVARES, FELIPE; GULICH, DAMIÁN; ROSSO, OSVALDO A.; ZUNINO, LUCIANO; PÉREZ, DARÍO G.; OLIVARES, FELIPE

Physical Review E

American Physical Society

Año: 2017 vol. 96 p. 1 - 7

2470-0045

We have experimentally quantified the temporal structural diversity from the coordinate fluctuations of a laserbeam propagating through isotropic optical turbulence. The main focus here is on the characterization of thelong-range correlations in the wandering of a thin Gaussian laser beam over a screen after propagating througha turbulent medium. To fulfill this goal, a laboratory-controlled experiment was conducted in which coordinatefluctuations of the laser beam were recorded at a sufficiently high sampling rate for a wide range of turbulentconditions. Horizontal and vertical displacements of the laser beam centroid were subsequently analyzed byimplementing the symbolic technique based on ordinal patterns to estimate the well-known permutation entropy.We show that the permutation entropy estimations at multiple time scales evidence an interplay between differentdynamical behaviors. More specifically, a crossover between two different scaling regimes is observed. Weconfirm a transition from an integrated stochastic process contaminated with electronic noise to a fractionalBrownian motion with a Hurst exponent H = 5/6 as the sampling time increases. Besides, we are able toquantify, from the estimated entropy, the amount of electronic noise as a function of the turbulence strength.We have also demonstrated that these experimental observations are in very good agreement with numericalsimulations of noisy fractional Brownian motions with a well-defined crossover between two different scalingregimes.