Measurement of Turbulence-induced POAM · 2018-06-11 · Distribution A 3 Distribution A Photonic...
Transcript of Measurement of Turbulence-induced POAM · 2018-06-11 · Distribution A 3 Distribution A Photonic...
AFOSR Portfolio Review -- ASALT Lab
Measurement of Turbulence-induced POAM
5 November 2014
Dr. Darryl Sanchez (PI) Mr. Pat Kelly (PM)
Directed Energy Directorate Air Force Research Laboratory
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Outline
• Background -- review of POAM
• Review of Previous Results
• PAOM in Astrophysics
• POAM in Terrestrial Data
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Photonic Orbital Angular Momentum
• (Jackson, 1975) Angular momentum
• (Allen, 1992) OAM is carried by L-G beams • L-G beam can be created from H-G
beams using cylindrical lenses
• Jackson JD, "Classical Electrodynamics", 2nd ed, 1975 • Allen L, Phys. Rev. Lett. (1992) • van Enk SJ, Euro. Phys. Lett. (1994), van Enk SJ, J. Mod. Phys. (1994) • Chen XS, Phys. Rev. Lett. (2008)
intensity
orbital angular momentum (POAM)
wavelength
polarization coherence
• (van Enk, 1994) proper angular momentum operators, J = S + L • S = spin angular momentum = circular polarization
• L = orbital angular momentum
• (Chen, 2008) Gauge invariance (non-local)
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Near Zenith With longer atmospheric paths and
higher Cn2, POAM appears in the beam
Turbulence-induced POAM - 1
Observatory
Atmosphere
point source
• Fried DL, JOSA A, (1992) • Sanchez DJ, Optics Express, (2011)
Longer atmospheric paths
Higher Cn2
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Identification of Optical Vortices
Projections of the Helicity Spectrum
Trajectories of the triplets
t
x y
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Optical vortex trails are definitive proof of the presence of POAM in a traveling wave
Projections of the helicity spectrum capture the trajectories of the triples
The Helicity Spectrum Projections of the Helicity Spectrum
The triplets, (mk, xk, yk), fully describe the POAM component of the beam
• C encloses a single branch point at (xk,yk) • mk is the helicity of that branch point
Construction of the Helicity Spectrum
Sloping trails in proj(H) definitively identify POAM
• Oesch DW, Optics Express (2010) • Sanchez DJ, Optics Express (2011a) • Sanchez DJ, Optics Express (2011b)
• Oesch DW, Optics Express (2012a) • Oesch DW, Optics Express (2012b) • Oesch DW, Optical Eng (2012)
• Oesch DW, Optics Express (2013) • Sanchez DJ, A&A (2013) • Oesch DW, A&A (2014)
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Outline
• Background -- review of POAM
• Review of Previous Results
• POAM in Astrophysics
• POAM in Terrestrial Data
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The Natural Geometry of Turbulence-induced POAM
Creation Pairs & the Natural Geometry of TI-POAM
Creation Pairs • follow directly from causality ==> Branch points are created
infinitesimally close together in pairs of opposite helicity
• Sanchez DJ, Opt Exp (2011) • Sanchez DJ, SPIE (2009)
Experimental Data
Creation Pair
The Natural Geometry Creation Pairs in Simulation
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Summary of Previous ASALT Results
Velocity
Number of Layers Strength and Distance
Persistence/Creation Pairs
• Oesch DW, Optics Express (2012b) • Oesch DW, Optics Express (2012a) • Oesch DW, OSA FIO (2012) • Sanchez DJ, Optics Express (2011b) • Sanchez DJ, Optics Express (2011a) • Sanchez DJ, SPIE (2009)
• Oesch DW, Opt Eng (2012) • Oesch DW, SPIE (2009) • Oesch DW, SPIE (2010)
• Oesch DW, OSA FiO (2011) • Oesch DW, SPIE (2010) • Brennan TJ, OSA pcDVT (2014)
SD Covariance
t
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Outline
• Background
• Review of Previous Results
• POAM in Astrophysics
• POAM in Terrestrial Data
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2011 Observation of Astronomical POAM
49 Ceti HR 1895 HR 1784
HR 1529
HR 1577
• 3.5m telescope at Starfire Optical Range, Kirtland AFB
• 24x24 Shack-Hartmann wavefront sensor • open loop frame rate = 2 KHz • λ = 450-650 nm • duration = 10 sec or 20 sec
Astronomical TAMA exhibit the same characteristics as Earth’s atmosphere
PIGs in the ORION nebula
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POAM in the cosmos
017.017.0 ±=η
219.2 mov=ρ
txH −
Estimation of POAM via [[G]]
Estimation of POAM via eimφ
Estimation of POAM using H
First ever measurement of POAM in the cosmos
• DW Oesch, et al., Opt. Express, 21(5), 2013. • DJ Sanchez, et al, A&A, 556(A130), 2013. • DW Oesch and DJ Sanchez, A&A, 2014.
• SOR 3.5m telescope • 5 stars, 10 datasets
Star Name η
mean Nσ
49 Ceti 0.06 6 HR 1529 0.07 5
0.06 6 HR 1577 0.04 5
0.03 5 HR 1784 0.04 5
0.03 4 HR 1895 0.17 9
0.05 6 0.04 6
POAM has been found in every instance when propagating
through extended turbulence
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Outline
• Background
• Review of Previous Results
• POAM in Astrophysics
• POAM in Terrestrial Data -- the RACHL experiment
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• 3.2 Km path across a valley • HeNe laser as the source • data collection on 22 days • morning to mid-day (mostly)
The RACHL Experiment Description
• Meade 40cm telescope • Shack-Hartmann WFS
• 32x32 subapertures (d=2cm) • 18x18 pixels/subap
SORTS instrument
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The RACHL Experiment From Spots to Params
Spots
Standard parameters, r0, σI2, fG, D(t)
ASALT lab parameters, ρ, H
Hx and Hy (BP trails)
Phase covariance (racetrack mode)
Correlations
Slopes
• Brennan TJ, SPIE (2010) • Farrell TC, SPIE (2012) • Brennan TJ, OSA pcDVT (2013)
• Farrell TC, OSA pcDVT (2013) • Oesch DW, Optics Express (2013)
• Brennan TJ, OSA pcDVT (2014) • Farrell TC, OSA pcDVT (2014)
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Brennan Coefficient
Fried Parameter Scintillation Index (Rytov Parameter)
Inner Scale
The RACHL Experiment Test Conditions
BP density Anisotropy
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Fried Parameter Scintillation Index (Rytov Parameter)
Inner Scale
The RACHL Experiment Test Conditions
BP density Anisotropy
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The RACHL Experiment Instantaneous Correlation (Sample)
ρ and r0
Instantaneous Anti-correlation
Fried parameter
Optical Vortex density
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The device can measure ρ=0
The RACHL Experiment POAM in the beam - 1
Fried parameter
Optical Vortex density
Projxt{H}
Projyt{H}
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Trails on 24 July 2014 at 11:38:43
The RACHL Experiment POAM in the beam - 2
Fried parameter
Optical Vortex density
Projxt{H}
Projyt{H}
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Trails on 24 July 2014 at 11:38:43
The RACHL Experiment POAM in the beam - 3
Fried parameter
Optical Vortex density
Projxt{H}
Projyt{H}
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Trails on 24 Jul 2014 11:38:43
The RACHL Experiment POAM in the beam - 4
Trails on 7 Aug 2014 10:55:16
Projxt{H}
Projyt{H}
Projxt{H}
Projyt{H}
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Trails on 2 Sept 2014 at 10:27:30
The RACHL Experiment POAM in the beam - 5
Trails on 4 Sept 2014 at 12:16:47
Projxt{H}
Projyt{H}
Projxt{H}
Projyt{H}
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Correlation of Parameters
Functional Dependence
Covariance of SD phase
The RACHL Experiment Future Publications
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Summary
• POAM is a recently discovered 5th property of light
• Turbulence creates POAM
• We have measured POAM from astronomical sources
• POAM is seen in great quantities in the RACHL data
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The Starfire Optical Range Summer 2011
Questions?