scholarly journals Experimental determination of thermal turbulence effects on a propagating laser beam

Open Physics ◽  
2015 ◽  
Vol 13 (1) ◽  
Author(s):  
Sphumelele C. Ndlovu ◽  
Naven Chetty
Keyword(s):  
Laser Beam ◽  
Atmospheric Turbulence ◽  
Laser Beams ◽  
Reliable Technique ◽  
Thermal Turbulence ◽  
Turbulence Effects ◽  
The Military ◽  
Atmospheric Systems ◽  
Turbulence Parameters

AbstractThe effect of turbulence on propagating laser beams has been a subject of interest since the evolution of lasers back in 1959. In this work, an inexpensive and reliable technique for producing interferograms using a point diffraction interferometer (PDI) was considered to experimentally study the turbulence effects on a laser beam propagating through air. The formed interferograms from a propagating beamwere observed and digitally processed to study the strength of atmospheric turbulence. This technique was found to be sensitive enough to detect changes in applied temperature with distance between the simulated turbulence and laser path. These preliminary findings indicated that we can use a PDI method to detect and localise atmospheric turbulence parameters. Such parameters are very important for use in the military (defence laser weapons) and this is vital for South Africa (SA) since it has natural resources, is involved in peace keeping and mediation for other countries, and hence must have a strong defence system that will be able to locate, detect and destroy incoming missiles and other threatening atmospheric systems in order to protect its environment and avoid the initiation of countermeasures on its land.

EXPERIMENTAL VERIFICATION OF THE TURBULENT EFFECTS ON LASER BEAM PROPAGATION IN SPACE

Atmósfera ◽  
2015 ◽  
Vol 27 (4) ◽  
pp. 385-401
Author(s):  
SHIVAN M. AUGUSTINE ◽  
NAVEN CHETTY
Keyword(s):  
Laser Beam ◽  
Turbulence Model ◽  
Thermal Effects ◽  
Fourier Transforms ◽  
Scintillation Index ◽  
Weak Turbulence ◽  
Laser Beam Propagation ◽  
Thermal Turbulence ◽  
Turbulence Effects ◽  
Path Lengths

In this work, we have modified an existing experimental setup to fully classify the thermal effects on a laser beam propagating in air. Improvements made to the setup include a new, more powerful laser, a precision designed turbulence delivery system, an imbedded pressure sensor, and a platform for height adjustability between the laser beam and the turbulence model. The setup was not only able to reproduce previous results exactly but also allowed new data for the turbulence strength C2n, the Rytov variance (scintillation) and the coherence diameter (Fried’s parameter) to be successfully measured. Analysis of the produced interferograms has been discussed using fast Fourier transforms. The results confirm, within the Kolmogorov regime, that phase and intensity fluctuations increase relative to temperature. The turbulent region exhibited very strong disturbances, in the range of 1.1 × 10–12 m–2/3 to 2.7 × 10–12 m–2/3. In spite of the strong turbulence strength, scintillation proved otherwise, since the condition for a weak turbulence environment was determined in the laboratory and a low scintillation index was to be expected. This is as a result of the relatively short propagation distances achieved in the laboratory. In the open atmosphere, path lengths extend over vast distances and in order for turbulent effects to be realized, the turbulence model must generate stronger turbulence. The model was, therefore, able to demonstrate its ability to fully quantify and determine the thermal turbulence effects on a propagating laser beam.

Modified Methods for Image Processing of Laser Beam Profiles

2020 ◽  
pp. 161-198
Author(s):  
Sergii Bilan
Keyword(s):  
Image Processing ◽  
Information Processing ◽  
Laser Radiation ◽  
Laser Beam ◽  
Laser Beams ◽  
Software Model ◽  
Image Contour ◽  
Laser Profile

The chapter is devoted to the analysis of the object of the study and highlighted its features as a means of information processing. The review of the existing methods of processing images of the profiles of laser beams, the principles of the operation of systems on the basis of similar algorithms, an analysis of the accuracy of the determination of the energy and geometric centers of the beam of laser beam, its diameter, and the differences of laser radiation are carred out. On the basis of the introduced criterion for estimating the symmetry of the contour of an image of a laser profile, a method for finding the optimal center for such an image is proposed. A comparative software model of effective methods for analysis of laser radiation parameters, namely, the search for laser image contour centers and the determination of the diameter of a laser beam, was constructed.

Atmospheric Turbulence Effects on the Phase of Laser Beams

1974 ◽  
Vol 13 (7) ◽  
pp. 1582 ◽  
Author(s):  
Mario Bertolotti ◽  
Mario Carnevale ◽  
Ludovico Muzii ◽  
Daniele Sette
Keyword(s):  
Atmospheric Turbulence ◽  
Laser Beams ◽  
Turbulence Effects ◽  
Atmospheric Turbulence Effects

Implementing Artificial Intelligence in Predicting Metrics for Characterizing Laser Propagation in Atmospheric Turbulence

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Diego Alberto Lozano Jimenez ◽  
V. M.Krushnarao Kotteda ◽  
Vinod Kumar ◽  
V. S. Rao Gudimetla
Keyword(s):  
Machine Learning ◽  
Laser Beam ◽  
Atmospheric Turbulence ◽  
Language Processing ◽  
Large Scale ◽  
Learning Algorithms ◽  
Machine Learning Algorithms ◽  
Outer Scale ◽  
Laser Propagation ◽  
Turbulence Effects

The effects of a laser beam propagating through atmospheric turbulence are investigated using the phase screen approach. Turbulence effects are modeled by the Kolmogorov description of the energy cascade theory, and outer scale effect is implemented by the von Kármán refractive power spectral density. In this study, we analyze a plane wave propagating through varying atmospheric horizontal paths. An important consideration for the laser beam propagation of long distances is the random variations in the refractive index due to atmospheric turbulence. To characterize the random behavior, statistical analysis of the phase data and related metrics are examined at the output signal. We train three different machine learning algorithms in tensorflow library with the data at varying propagation lengths, outer scale lengths, and levels of turbulence intensity to predict statistical parameters that describe the atmospheric turbulence effects on laser propagation. tensorflow is an interface for demonstrating machine learning algorithms and an implementation for executing such algorithms on a wide variety of heterogeneous systems, ranging from mobile devices such as phones and tablets to large-scale distributed systems and thousands of computational devices such as GPU cards. The library contains a wide variety of algorithms including training and inference algorithms for deep neural network models. Therefore, it has been used for deploying machine learning systems in many fields including speech recognition, computer vision, natural language processing, and text mining.

Estimating Atmospheric Turbulence Parameters from the Envelopes of Radio Acoustic Signals

2001 ◽  
Vol 55 (8) ◽  
pp. 5
Author(s):  
V. M. Kartashov ◽  
V. A. Petrov ◽  
Ye. G. Proshkin ◽  
G. I. Sidorov
Keyword(s):  
Atmospheric Turbulence ◽  
Acoustic Signals ◽  
Turbulence Parameters
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