Environment MIDN Gabe Collins, USN MIDN Charles Stabler, USN U.S. - - PowerPoint PPT Presentation

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Environment MIDN Gabe Collins, USN MIDN Charles Stabler, USN U.S. - - PowerPoint PPT Presentation

Oct 15, 2022 629 likes •858 views

Laser Propagation in an Underwater Environment MIDN Gabe Collins, USN MIDN Charles Stabler, USN U.S. Naval Academy Weapons and U.S. Naval Academy Weapons and Systems Engineering Department Systems Engineering Department Distribution

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SLIDE 1

MIDN Gabe Collins, USN U.S. Naval Academy Weapons and Systems Engineering Department

Laser Propagation in an Underwater Environment

MIDN Charles Stabler, USN U.S. Naval Academy Weapons and Systems Engineering Department

Distribution Statement: A

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SLIDE 2

Motivation

Detection of: ➔Optical Wireless Communication Beams

Distribution Statement A

Image from SA Photonics

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SLIDE 3

Project Objective

To study different types of laser beams propagating and scattering underwater to find an optimal method of detection.

Distribution Statement A

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SLIDE 4

The Scenarios

  • Scenario 1: Calm Water
  • Scenario 2: Turbulent Water created with 12V pump

Values Measured

  • Mean Intensity
  • Scintillation Index
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SLIDE 5

Spatial Light Modulation

  • SPATIALLY - beamlets created from incident beam and differ

in size

  • PARTIALLY COHERENT - beamlets differ in phase
  • MULTI - “flat top” formed of multiple beamlets
  • GAUSSIAN - shape of beamlets
  • SHELL - temporal changes
  • BEAM – reconstruction of beam from beamlets

Distribution Statement A

Image from Meadowlark Optics

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SLIDE 6

The Beams

2 mW HeNe Source

  • Unexpanded
  • 10x Expanded
  • Less Spatially Coherent
  • More Spatially Coherent

Distribution Statement A

Beam Type Beam Number Unexpanded 1 Expanded 2 Less Coherent 3 More Coherent 4

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SLIDE 7

Equipment Setup

Distribution Statement A

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SLIDE 8

Distribution Statement A

Mean Intensity Comparison, Scattering View, of Gaussian and Spatial Modulated Beams in Calm and Turbulent Water

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SLIDE 9

Scattering of the Beams in Calm Water

Distribution Statement A

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SLIDE 10

Distribution Statement A

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SLIDE 11

Distribution Statement A

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SLIDE 12

Scintillation Index for Propagation in Calm Water

Distribution Statement A

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SLIDE 13

Summary of Results in Calm Water

Scattering: Intensity useful for detection of Beams 1 and 2 Scintillation index useful for detection of Beams 3 and 4 Propagation: Intensity useful for detection of Beams 1 and 2 Scintillation index useful for detection of Beams 3 and 4

Distribution Statement A

Beam Type Beam Number Unexpanded 1 Expanded 2 Less Coherent 3 More Coherent 4

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SLIDE 14

Scattering of the Beams in Turbulent Water

Distribution Statement A

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SLIDE 15

Scintillation Index for Propagation in Turbulent Water

Distribution Statement A

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SLIDE 16
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SLIDE 17
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SLIDE 18
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SLIDE 19
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SLIDE 20

Summary of Results in Turbulent Water

Scattering: Intensity useful for detection of Beams 1 and 2 Scintillation index useful for detection of Beams 3 and 4, especially so for Beam 1 Propagation: Intensity useful for detection of Beams 1 and 2 Scintillation index useful for detection of Beams 3 and 4

Distribution Statement A

Beam Type Beam Number Unexpanded 1 Expanded 2 Less Coherent 3 More Coherent 4

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SLIDE 21

Conclusion

SLM Beams - better detected by scintillation calculation Gaussian Beams - better detected by relative intensity measurement Lessons Learned...

Distribution Statement A

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SLIDE 22

Acknowledgements

Joe Bradshaw, Technical Support Division Norm Tyson, Technical Support Division Nick Eagle, Technical Support Division