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Airborne Measurement of Atmospheric-Induced Beam Jitter.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Airborne Measurement of Atmospheric-Induced Beam Jitter./
Author:	Kalensky, Matthew.
Description:	1 online resource (187 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 83-11, Section: B.
Contained By:	Dissertations Abstracts International83-11B.
Subject:	Aerospace engineering. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29065130click for full text (PQDT)
ISBN:	9798438723639

Airborne Measurement of Atmospheric-Induced Beam Jitter.
Kalensky, Matthew.

Airborne Measurement of Atmospheric-Induced Beam Jitter. - 1 online resource (187 pages)

Source: Dissertations Abstracts International, Volume: 83-11, Section: B.

Thesis (Ph.D.)--University of Notre Dame, 2022.

Includes bibliographical references

When a laser beam propagates through a field of varying index of refraction, its wavefront becomes optically distorted. The distortions imposed onto the wavefront resulting from these index-of-refraction non-uniformities can be categorized into the mean, tip, and tilt (tip/tilt) components, as well as variations over the laser beam diameter referred to as higher-order disturbances. While higher-order disturbances cause the laser beam to diffract and spread energy out in the far-field, tip/tilt causes the beam to deflect from its original path. This is caused by propagating the laser through optical turbulence structures larger than or on the order of the size of the beam diameter. The dynamic, net deflection of the beam in the far-field caused by tip/tilt is referred to as jitter. Beam jitter poses a serious problem for tracking in directed energy applications.The work presented in this dissertation sought to make in-flight experimental measurements of the tip/tilt imposed onto a laser beam by the atmosphere. The measurement of tip/tilt is challenging since the optical distortions caused by mechanical contamination in the form of aircraft platform vibration and aerodynamic buffeting also manifest as tip/tilt. A procedure referred to as the stitching method was used to remove the influence of mechanical contamination and quantify the atmospheric-induced component of tip/tilt. In order to generalize the results, the strength of the atmospheric optical turbulence environment through which the beam propagated was also quantified. From these results, it was found that the tip/tilt imposed onto the beam aligned with what analytic solutions predict and that the optical turbulence environment had Kolmogorov-like characteristics. Using both simulated and experimentally-measured turbulence-induced tilt time series, realistic tilt compensation approaches could be studied. It was shown that current approaches underpredict the bandwidth required to sufficiently compensate for tip/tilt imposed onto the beam. Based on the developments presented in this dissertation, suggestions are provided on how tracking can be improved in realistic digital control systems.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798438723639Subjects--Topical Terms:

1002622
Aerospace engineering.
Subjects--Index Terms:

Adaptive opticsIndex Terms--Genre/Form:

542853
Electronic books.

Airborne Measurement of Atmospheric-Induced Beam Jitter.
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520 $a When a laser beam propagates through a field of varying index of refraction, its wavefront becomes optically distorted. The distortions imposed onto the wavefront resulting from these index-of-refraction non-uniformities can be categorized into the mean, tip, and tilt (tip/tilt) components, as well as variations over the laser beam diameter referred to as higher-order disturbances. While higher-order disturbances cause the laser beam to diffract and spread energy out in the far-field, tip/tilt causes the beam to deflect from its original path. This is caused by propagating the laser through optical turbulence structures larger than or on the order of the size of the beam diameter. The dynamic, net deflection of the beam in the far-field caused by tip/tilt is referred to as jitter. Beam jitter poses a serious problem for tracking in directed energy applications.The work presented in this dissertation sought to make in-flight experimental measurements of the tip/tilt imposed onto a laser beam by the atmosphere. The measurement of tip/tilt is challenging since the optical distortions caused by mechanical contamination in the form of aircraft platform vibration and aerodynamic buffeting also manifest as tip/tilt. A procedure referred to as the stitching method was used to remove the influence of mechanical contamination and quantify the atmospheric-induced component of tip/tilt. In order to generalize the results, the strength of the atmospheric optical turbulence environment through which the beam propagated was also quantified. From these results, it was found that the tip/tilt imposed onto the beam aligned with what analytic solutions predict and that the optical turbulence environment had Kolmogorov-like characteristics. Using both simulated and experimentally-measured turbulence-induced tilt time series, realistic tilt compensation approaches could be studied. It was shown that current approaches underpredict the bandwidth required to sufficiently compensate for tip/tilt imposed onto the beam. Based on the developments presented in this dissertation, suggestions are provided on how tracking can be improved in realistic digital control systems.
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