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

Turbulence-induced POAM - 2

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?