LOIS and new radio and radar methods - Swedish Institute of Space ...

LOIS and new radio and radar methods 

Bo Thidé 

Swedish Institute of Space Physics, IRF, Uppsala, Sweden 

LOIS Space Centre, Växjö, Sweden 

and the LOIS Photon Orbital Angular Momentum collaboration 

J. Bergman, S. Mohammadi, H. Then, T. Carozzi, L. Daldorff, R. Karlsson, 

T. Mendonca and W. Baan 

Physics in 

Space 

Programme 

Seminar 

IDE, University of Halmstad 

5 Sep, 2008 

LOFAR 

Outrigger in 

Scandinavia

Where it all started: Cosmic hydrogen radiates 

narrow band radio signals at 1420.4 MHz 

The 21 cm λ H hyperfine splitting line 

BoThidé Seminar, IDE, Univerity of Halmstad, 5 Sep, 2008 

2

Conventional radio diagnostics. Can we do better? 

The Westerbork array of 14 dishes, each 25 m in diameter sees nearby 

objects emitting 1420.4 MHz (21 cm λ H hyperfine splitting) lines 

M31 (Andromeda, Local group) 


3

Answer: New generation digital radio telescopes 

LOFAR 

Low Frequency Array (10–240 

MHz). Test station at Exloo 

operational 2004, full scale 

deployment of 25 000 antennas in 

progress. 

LOIS 

LOFAR In Scandinavia. Test 

station near Växjö operational 

2004, fast fibre network, 

supercomputer 2005. Second test 

station near Ronneby, 2008. Fullscale 

station in Poznan, Poland, in 

the 2009-2011 timeframe. 

SKA 

Square Kilometre Array. Australia 

or South Africa, ~2020. Very 

sensitive (5 000 000 antennas!). 


4

3D polarimetry utilising that E(t,x) is a polar vector 

and B(t,x) an axial vector (pseudovector) 


5

LOIS: Arrays of tripole antennas to sample the 

entire EM field vectors both in time and space 


6

Three orthogonal loop antennas probe the 3D magnetic 

field pseudovectors 


7

LOIS resources 

Supercomputer cluster (two SUR grants 

from IBM) and part of the LOIS Test 

Station outside Växjö, SE. 

Lars Daldorff, Axel Guthmann and the IBM system 

B.T. and Willem Baan 

at the LOIS Test Station. 


8

Next LOIS station under construction in Ronneby 


9

Next LOIS station control centre at BTH in Ronneby 


10

Europe’s first electromagnetically and acoustically 

quiet chamber at the Ångström Laboratory, Uppsala 


11

Lorentz’s microscopic Maxwell equations 

for the EM field (1903) 

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. In fact there are 23 exact, plus an as yet unknown 

number of approximate, conservation laws. 


12

Conserved quantities in a closed electromechanical 

system (matter + EM fields) [Boyer, 2005] (1) 

Homogeneity in time => conservation of system energy 

(no EMF, no radiation; cf. Poynting’s theorem): 

Homogeneity in space => conservation of system linear 

momentum (gives, e.g., rise to EM Doppler shift): 

Foundation of conventional ‘linear momentum’ radiation. 


13

Conserved quantities in a closed electromechanical 

system (matter + EM fields) [Boyer, 2005] (2) 

Invariance under proper Lorentz transformations => 

conservation of system centre of energy: 

Isotropy in space => conservation of system angular 

momentum: 

Foundations of ‘angular momentum’ radio. 


14

Total EM field angular momentum 

For radiation beams, the EM field angular momentum J EM 

can be separated into two parts [van Enk & Nienhuis, 1992]: 

The first part is the EM orbital angular momentum (OAM) 

L EM , and the second part is the EM spin angular momentum 

(SAM) S EM , a.k.a. wave polarisation. 

NB: In general, both EM linear momentum p EM , and EM 

angular momentum J EM = L EM + S EM are radiated all the way 

out to the far zone! 


15

Standard textbooks show that EM 

angular momentum is radiated 

all the way out to infinity 


16

Difference between polarisation (spin angular momentum, 

SAM) and orbital angular momentum (OAM) 


17

EM beam with circular polarisation 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 

Sjöholm and Palmer, 2007 


18

EM beams on the same frequency but with 

different OAM do not interfere with each other! 

M. J. Padgett, J. Leach et al., U. Glasgow, UK; Royal Society 

l=+1 

l=+3 

l= -4 

Spiraling Poynting vectors! 


19

Micromechanical action of SAM and OAM 

Particles of sizes 1–3 μm irradiated by SAM/OAM laser beams 

Spin angular momentum s = 1 Orbital angular momentum l = 8 


20

Pack EM beams with much more data by 

utilising topological degrees of freedom 


21

Comment on the use of POAM 


22

OAM now coming to the fore in astrophysics 


23

Very readable paper on POAM in astrophysics 


24

New ideas – New audiences 


25

Imparting OAM onto an EM beam (laser, mm wave) 

with the help of a hologram 


26

Imparting OAM onto an EM beam (laser, mm wave) 

with the help of a spiral plate 


27

Observations at 94 GHz of angular momentum 

induced rotational (azimuthal) Doppler shift 


28

Exotic types of Poynting flux radiation patterns 

and corresponding instantaneous E field vectors 


29

Field vector sensing means total configurability 


30

Further theoretical studies and computer experiments 


31

Further theoretical studies and computer experiments 


32

A rich set of EM conservation laws 

1 

2 

1 

2 

1 

2 

1 

2 

1 

2 

1 

2 

1 

2 

1 

2 

ε 

0 2 2 2 

( H 

+ 

+ H 

− 

) = ( E + c B ) 

1 

∗ 

( H − H ) = Im[ E⋅B 

] 

1 

∗ 

( K + K ) = Re[ E× 

B ] 

0 

0 

ε 

0 

∗ 2 ∗ 

( K − K ) = − Im[ E× 

E + c B× 

B ] 

~ ~ ij 

i j∗ 

2 i j∗ 

( T + T ) = δ u −ε 

Re[ E E + c B B ] 

+ 

~ ~ ij 1 i j∗ 

i j∗ 

( T − T ) = δ v − Im[ E B − B E ] 

+ 

Re 

c 

1 

Re 

2c 

1 

+ 

2 

2 

1 

∗ 

[ j⋅( G + G )] = Re[ j⋅E 

] 

∗ 

[ j⋅( G − G )] = Im[ j⋅B 

] 

RS RS 

∗ ∗ 

( F + F ) = Re[ ρE 

+ j× 

B ] 

2 

0 

0 

= P 

1 ∂u 

= 

c ∂t 

1 ∂v 

= 

c ∂t 

= F 

Mech 

Lorentz 

∗ 

RS RS 

⎡ 

∗ j× 

E ⎤ 

Spin 

( F − F ) = Im cρB 

− = F 

+ 

+ 

+ 

+ 

− 

− 

− 

− 

− 

+ 

+ 

+ 

+ 

Z 

Z 

− 

− 

⎢ 

⎣ 

Z 

c 

= v 

c 

= u 

⎥ 

⎦ 

Kinetic energy 

Spin energy 

Linear momentum 

= V 

= U 

Mech 

= T 

Spin angular momentum 

Stress tensor 

Spin stress tensor 

Electro-mechanical power 

Spin-mechanical power 

Lorentz force 

Spin force (torque) 


33

LOIS has measured the spin angular momenum V 

in ionospheric radio signals since 2003 


34

Numerical simulation of E for s=1 and l=1 

Left: Power density and E field topology 

Right: Spin power density and spin angular momentum 


35

Radio beam topology degrees of freedom 

Left: Conventional linear momentum (Poynting) flux and E 

Right: Orbital angular momentum flux 


36

Challenge: Ionospheric and atmospheric turbulence 

distort low-frequency radio signals from outer space 

Vorticity due to nonlinear plasma turbulence distort radio signals during their 

passage through the ionosphere. Find a way to compensate (‘self-calibrate’) for 

this. Data from observations at VLA at 75 MHz. 


37

Systematic plasma EM turbulence diagnostics 

Complements – and is supplemented by – radars, satellites, optics etc. 

B. Thidé et al., PRL, 1981 


38

Experimental tests: Ionospheric turbulence on demand 

HF pump frequency swept continuously up and down across 4f 

ce 

at Sura, Russia 

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 4 th electron gyroharmonic. 

Pump 

 

60 kHz 

(Click for animation) 

5340 kHz 4fce 

5540 kHz 


39

2D polarimetric signatures of EM radiation from 

parametrically induced ionospheric plasma turbulence 

Essentially 2D Stokes parameters 

Concomitant symmetry group: SU(2) 

Expansion to 3D [SU(3)] straightforward 


40

First OAM/vorticity radio experiment in the 

ionospheric plasma (HAARP, Alaska, 27 Feb 2008) 


41

E field topology degrees of freedom: Precession 

vs. nutation for circular and elliptic polarization 

Circular polarization, OAM l=1, Precession 

Circular polarization, OAM l=1, Nutation 

Elliptic polarization, OAM l=1, Precession 

Elliptic polarization, OAM l=1, Nutation 


42

‘Textbook’ radar examples 

Half-wave plate, Beth 1936 

Perfect reflector, 

solar sail 

Linear polarizer, 

Cararra 1949 

ΔP 

= 0 

ΔV 

= 

Spin Spin 

2V 

∝ F ∝ τ 

ΔP 

= 2P 

∝ F 

ΔV 

= 0 

Lorentz 

ΔP 

= P / 2 

ΔV 

= V 


43

OAM spectrum probing – a new diagnostic under 

development in optics. Implement in radio/radar! 

Recent digital spiral imaging experiments (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… 


44

Spiral (OAM) spectrum imaging results 

…and its response 


45

First experimental verification of free-space 

information transfer using OAM topological encoding 


46

OAM makes a new (spiral) frequency Ω available 

Interesting consequences for radio communications 


47

The radio frequency spectrum is limited – and 

expensive! 

Spiraling Poynting vectors! 


48

Hyperentagled SAM and OAM photon states break the 

linear-optics channel capacity threshold 


49

Recent LOIS development for astroparticle physics 

• Ultrahigh energy neutrino 

detector 

• For detection of neutrino 

induced radio pulses in the 

Antarctic ice 


50

Recent LOIS development for space physics 

and space communications 

• Radio-on-chip, 33×33 mm 2 , 4 grams 

– Bare die components on silicon 


51

Recent initiatives for space – Go to the Moon 

• Radio-on-chip, 33×33 mm 2 , 4 grams 

– Bare die components on silicon 


52

Conclusions 

• Using all ‘degrees of freedom’ (conserved quantities) 

allows full characterization and extraction of all 

information carried by beams of EM waves/photons 

• Has already provided better diagnostics in laser 

physics and revolutionised free-space communications 

• Can use conventional radio techniques to apply these 

new results to the radio domain 

• The radio domain results hold great promise for new 

fundamental optics and improved remote diagnostics 

• World’s first OAM radio laboratory at Ångström Lab, 

Uppsala, is now under construction 


53

Thank you for your attention 

Radio is much more than frequency, amplitude and phase! 


54

LOIS and new radio and radar methods - Swedish Institute of Space ...

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