Very readable paper on photon orbital angular momentum. 10 ... Instantaneous field vectors across an antenna ... Orbital angular momentum due to azimuthal.
The Use of Electromagnetic Angular Momentum in Science and Technology Bo Thidé Swedish Institute of Space Physics, IRF, Uppsala, Sweden That far-zone OAM from a dipole is generated by near-zone
with contributions from
Fabrizio Tamburini Department of Astronomy, University of Padova, Italy and
LOFAR/LOIS project members Uppsala and elsewhere
Scientific lecture, Rennes, France, 25 September, 2010
Conventional radio multipath diversity utilises three extra electromagnetic degrees of freedom The first multipath diversity paper
The physics behind multipath diversity
Reflection, i.e. space inversion x → x´ = -x is represented physically by the transformations
implying the threefold EM symmetry/three extra degrees of freedom:
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Is there underutilised information in (classical) electromagnetic fields and radiation? Microscopic Maxwell-Lorentz equations
Symmetric under inhomogeneous Lorentz transformations. The concomitant Lie group is the 10-dimensional Poincaré group P(10). According to Noether’s theorem there therefore exist 10 conserved EM quantities. Further analysis shows that there exist 23 exact firstorder, continuous symmetries/conserved quantities (in vacuo), plus a number of approximate conservation laws [Ibragimov, 2008]. Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Conserved quantities in a closed electromechanical system (plasma + EM fields) [Boyer, 2005] (1) Homogeneity in time => conservation of system energy (Poynting’s theorem):
Homogeneity in space => conservation of system linear momentum (gives rise to translational Doppler shift):
This is the physical foundation of conventional radio. NB: Linear EM momentum = integrated Poynting vector/c Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Conserved quantities in a closed electromechanical system (matter + EM fields) [Boyer, 2005] (2) Isotropy in space => conservation of system angular momentum (gives rise to azimuthal Doppler shift):
The first part is the mechanical angular momentum Jmech . The second part is the EM angular momentum Jfield. Foundation of ‘angular momentum’ radio or ‘dual radio’. Invariance under proper Lorentz transformations => conservation of system centre of energy:
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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EM angular momentum is a conserved physical observable. Just like the linear momentum (Poynting vector), it that can carry information over huge distances
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Hyperentangled SAM and OAM photon states break the linear-optics channel capacity threshold
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Angular momentum of light mentioned by Maxwell in the 1860’s and studied by Poynting already in 1909
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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That far-zone OAM from a dipole is generated by near-zone E fields was shown 1914 by Max Abraham
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Very readable paper on photon orbital angular momentum
Scientific lecture, Rennes, France, 25 September 2010
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Very nice review on photon orbital angular momentum
Scientific lecture, Rennes, France, 25 September 2010
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EM angular momentum may be decomposed into spin (SAM), orbital (OAM) and a third term
Scientific lecture, Rennes, France, 25 September 2010
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EM angular momentum may be decomposed into spin (SAM), orbital (OAM) and a third term
Scientific lecture, Rennes, France, 25 September 2010
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Classical EM linear momentum and angular momentum can be expressed in QM operators EM field total angular momentum (TAM) around the origin 0:
Where A(t,x) is the vector potential and Photon spin angular momentum (SAM) ~ polarisation Photon orbital angular momentum (OAM)
For each (temporal) Fourier component of the field
, where
Bo Thidé
Linear momentum operator
, where
SAM operator
, where
OAM operator
Scientific lecture, Rennes, France, 25 September 2010
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The OAM topological degree of freedom has revolutionised wireless communications
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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The conventional Shannon dimensionality of 2 can be exceeded by using OAM degrees of freedom
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Recent call for funding of practical “on-the-scene” information-rich applications using OAM etc.
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Radiation generation by utilising the rotational degrees of freedom of the EM field
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Difference between polarisation (SAM) and orbital angular momentum (OAM)
Scientific lecture, Rennes, France, 25 September 2010
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EM beam with circular polarisation (SAM) S but no orbital angular momentum (OAM) L Phase fronts (loci of constant phase) Optics (LG)
Radio
M. J. Padgett, J. Leach et al., U. Glasgow, UK; Royal Society
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
Sjöholm and Palmer, 2007 20
Instantaneous field vectors across an antenna array for a radio beam with circular SAM
Phase 0 deg Bo Thidé & Jan
Phase 45 deg
CSC Colloquium, SETI Institute, Mountain View, Scientific lecture, Rennes, France, 25 September 2010 21 CA, January 2, 2008
Different OAM states correspond to different topological charges (vortex winding numbers) M. J. Padgett, J. Leach et al., U. Glasgow, UK; Royal Society
l=+3
l=+1
l= -4
Bo Thidé
Spiraling Poynting/OAM vectors can carry a lot of extra information! The Jones matrix goes from 2×2 to 2(j+1)×2(j+1), j=s+l .
Scientific lecture, Rennes, France, 25 September 2010
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Instantaneous field vectors in a cross section of a radio beam carrying both SAM and OAM
Phase 0 deg Bo Thidé & Jan
Phase 45 deg
CSC Colloquium, SETI Institute, Mountain View, Scientific lecture, Rennes, France, 25 September 2010 23 CA, January 2, 2008
Orbital angular momentum due to azimuthal phase variation and beam (a)symmetry
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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The generation of beams carrying OAM proceeds thanks to the insertion in the optical path of a phase modifying device which imprints a certain vorticity on the phase distribution of the incident beam.
Imparting OAM onto a light beam Fork holograms are an example of such devices. If the hologram presents N bifurcations, then at the m-th diffraction order it imposes a OAM value equal to Nmħ (Vaziri et al. 2002).
On-axis
off-axis spectrum of OAM
Spiral Phase Plate
s
l = ∆n λ s = total thickness Δn = difference of refraction indices.
Fabrizio Tamburini
of
the
plate,
Scientific lecture, Rennes, France, 25 September 2010
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Conventional radio telescopes not sufficient. Can we do better? The array of fourteen 25 m dishes at Westerboork (NL), sees nearby objects emitting 1420.4 MHz (21 cm λ H hyperfine splitting) lines
M31 (Andromeda, Local group) Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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The Grand Challenge: Observe the first 21 cm radio line emitted after Big Bang!
Bo Thidé
REAL lecture, Seminar,Rennes, BTH, Ronneby, 23 September January, 2009 Scientific France, 25 2010
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Answer: New-generation wide-area radio telescopes with improved sensitivity, resolution and flexibility LOFAR Low Frequency Array (10–240 MHz). Test station at Exloo operational 2004, full-scale deployment of 25 000 antennas in progress. Must be able to handle data streams up to 23 Tbits/s.
LOIS LOFAR In Scandinavia. Pathfinder station near Växjö operational 2004, fast fibre network, supercomputer 2005. Prototype station near Ronneby, 2010. Full-scale station in Poznan, Poland, in the 2011-2013 timeframe.
SKA Square Kilometre Array. Australia or South Africa, ~2020. Very sensitive (5 000 000 antennas!). Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Radio OAM can be probed with LOFAR-type phased arrays. Best results with vector sensing antennas Thidé et al., Phys. Rev. Lett., 99, 087701, 2007
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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The OAM radio results agree with theory Theory predicts that a circular polarised radio beam in a pure OAM eigenstate with azimuthal phase dependence exp(ilφ), frequency ω, and energy H, should have a total angular momentum component JzEM = lH/ω along the z (beam) axis.
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Radio beam carrying both SAM and OAM Linear momentum (Poynting) flux and E(t,x) vs. OAM flux Mohammadi et al., IEEE Trans. Ant. Propag., Vol. 58 ,2009
Distribution of linear momentum (Poynting ) flux and E-field vectors Bo Thidé
Distribution of orbital angular momentum flux
Scientific lecture, Rennes, France, 25 September 2010
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Field vector sensing means total configurability
Excellent radio coronagraph for the solar corona and exoplanets! Scientific lecture, Rennes, France, 25 September 2010
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First real-world OAM coronagraph example T122 telescope, Asiago, Italy
Sufficient resolution for direct detection of extra-solar planets! Scientific lecture, Rennes, France, 25 September 2010
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LOIS 2nd generation prototype station, Ronneby To be augmented by two outer, concentric rings, with 16 and 24 radio units, respectively, for a total of 48 units with three dipoles each (funding permitting)
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Use large arrays with velectric and magnetic antennas that sample the entire EM field vector
To be first used in Venice, 2010 Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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3D vector antennas allow new types of diagnostics
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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LOIS has measured the photon spin current V in ionospheric radio signals since 2003
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Challenge: Ionospheric and atmospheric turbulence distort low-frequency radio signals from outer space Today it is possible to compensate (‘self-calibrate’) for amplitude and nonsingular phase distortion of signals propagation through the ionosphere. Data from observations at VLA (Very Large Array, NM, USA) at 74 MHz.
Bo Thidé
Asiago, 24October, Scientific lecture, Rennes, France,2008 25 September 2010
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Close collaboration with IBM Research, NY, on the analysis of streaming data from digital radio sensors
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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SEE as an on-demand space plasma EM turbulence diagnostics Complements – and supplements – optics, radars, satellites,etc.
BoThidé
Scientific lecture, Rennes, France, 25 September 2010
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Secondary HF radio emission dependence HF pump frequency swept continuously up and down across 4f at Sura, Russia on primary HF radio frequency ce
BUM hysteresis
HF excited secondary radiation (SEE) as recorded at the radio facility SURA near Nizhniy Novgorod, Russia, 1999. The HF pump frequency is swept across the ionospheric 4th electron gyroharmonic.
60 kHz
Pump
5340 kHz
(Click for animation)
4fce
BoThidé
5540 kHz
Scientific lecture, Rennes, France, 25 September 2010
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2D polarimetric signatures of EM radiation from space plasma turbulence induced by radio pumping
Essentially 2D Stokes parameters Concomitant symmetry group: SU(2) Expansion to 3D [SU(3)] straightforward Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
Anderson-Higgs mechanism affected by POAM
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Plasmons (Langmuir waves) can carry OAM but not SAM
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Nonlinear transfer of OAM radio ↔ plasma Brillouin = ion line Raman = plasma line
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Europe is leading the way
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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POAM in light around a Kerr black hole (Sgr A*)
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Sardinia Radio Telescope first to use radio OAM
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Observations at 94 GHz of angular momentum induced azimuthal (rotational) Doppler shift
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Rotational Doppler shift spectrum
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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OAM spectrum probing (spiral imaging) – a new scatter radar diagnostic Recent digital spiral imaging experiments (Ll. Torner et al., Opt. Express, 13, 873–881, 2005; Molina-Terriza et al., J. Eur. Opt. Soc., Rapid Publ., 2, 07014, 2007) have demonstrated that probing with OAM gives a wealth of new information about the object under study.
The stimulus…
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Spiral (OAM) spectrum imaging results
…and its response
Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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OAM detection of inhomogeneities (in transmission)
Bo Thidé & Jan
CSC Colloquium, SETI Institute, Mountain View, Scientific lecture, Rennes, France, 25 September 2010 53 CA, January 2, 2008
Thank you
....there may be more things in heaven and earth than even Maxwell had dreamt of … Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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Thank you for your attention
....there may be more things in heaven and earth than even Maxwell had dreamt of … Bo Thidé
Scientific lecture, Rennes, France, 25 September 2010
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