Bo Thidé Swedish Institute of Space Physics, IRF, Uppsala, Sweden LOIS Space Centre, Växjö, Sweden

Size: px

Start display at page:

Download "Bo Thidé Swedish Institute of Space Physics, IRF, Uppsala, Sweden LOIS Space Centre, Växjö, Sweden"

Alisha Curtis
6 years ago
Views:

The LOIS project The utilisation of electromagnetic orbital angular momentum

Uppsala, Sweden LOIS Space Centre, Växjö, Sweden with contributions from the

Mohammadi, A. Hast (Uppsala), R. Karlsson (Graz), T. Carozzi (Glasgow), H.

Gustavsson, N. Ibragimov, R. Khamitova. C. Svahnberg, H.-J.

Istomin (Lebedev Institute, Moscow), E. Weibust, B. Sjökvist (IBM Sweden), B.

1 The LOIS project The utilisation of electromagnetic orbital angular momentum in wireless communications Bo Thidé Swedish Institute of Space Physics, IRF, Uppsala, Sweden LOIS Space Centre, Växjö, Sweden with contributions from the LOIS OAM/radio topology collaboration J. Bergman, L. Daldorff, S. Mohammadi, A. Hast (Uppsala), R. Karlsson (Graz), T. Carozzi (Glasgow), H. Lundstedt (Lund), W. Löwe, W. Baan, M. Milrad (Växjö), M. Fredriksson, R. Gustavsson, N. Ibragimov, R. Khamitova. C. Svahnberg, H.-J. Zepernick (BTH), H. Then (Oldenburg), T. Mendonca (Lisbon), Ya. N. Istomin (Lebedev Institute, Moscow), E. Weibust, B. Sjökvist (IBM Sweden), B. Elmegreen, L. Amini, A. Biem, D. Turaga, and O. Verscheure (IBM Research, NY) REAL Seminar, BTH, Ronneby, 23 January, 2009

2 Where it all started: Cosmic hydrogen radiates strong, narrow-band radio signals at MHz The 21 cm λ H hyperfine splitting line Antenna length: 1 Å= λ! One of two 1-2 GHz telescopes on the roof of Ångström Lab, Uppsala 2

3 Conventional radio telescopes not sufficient. Can we do better? The array of fourteen 25 m dishes at Westerbork (NL), sees nearby objects emitting MHz (21 cm λ H hyperfine splitting) lines M31 (Andromeda, Local group) 3

4 The Grand Challenge: Observe the first 21 cm radio line emitted after Big Bang! 4

Answer: New-generation wide-area radio telescopes with improved sensitivity, resolution and flexibility LOFAR Low Frequency Array (10 240 MHz).

LOIS LOFAR In Scandinavia. Pathfinder station near Växjö operational 2004, fast fibre network, supercomputer 2005. Prototype station near Ronneby, 2008.

5 Answer: New-generation wide-area radio telescopes with improved sensitivity, resolution and flexibility LOFAR Low Frequency Array ( MHz). Test station at Exloo operational 2004, full-scale deployment of 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 Prototype station near Ronneby, Full-scale station in Poznan, Poland, in the timeframe. SKA Square Kilometre Array. Australia or South Africa, ~2020. Very sensitive ( antennas!). 5

6 LOIS radio idea: Sample the entire field vectors in time and space (LOIS stn true superset of LOFAR stn) 6

7 LOIS resources 2003 today (total ~ 2.5 MEur) Computer cluster (two SUR grants from IBM), currently in Uppsala. The control room at the LOIS Test Station Risinge/Växjö. Radio Sweden s transmitter located about 100 km south of the Växjö LOIS test station and 100 km south-west of the Ronneby prototype station site. Will be used for space radar tests. 9m 8m 6m antenna chamber, Ångström Lab, Uppsala Magnetometer, LOIS Test Station, Risinge/Växjö 7

8 IBM System S ideal for LOIS radio data streams 8

9 9

10 System S program for radio sensors 10

11 LOIS prototype station under construction in Ronneby To be augmented by two outer, concentric rings, with 16 and 32 radio units, respectively, for a total of 56 units with three dipoles each (funding permitting) 11

12 LOIS prototype station site at Angelskog, Ronneby Left photos taken 21 December, 2007, at 14:00 local time. Right photo from eniro.se 12

13 LOIS Angelskog prototype station sensitivity 3 antenna rings = 56 tripoles = 168 dipoles. 1 Jy = W/(m 2 Hz) 13

14 Three orthogonal dipole antennas sample E(t,x) Three orthogonal loop antennas sample B(t,x) 14

15 Even a single 3D vector antenna improves detection 15

16 EM beam with circular polarisation S but no orbital angular momentum (POAM) 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,

17 EM beams on the same frequency but with different OAM would be orthogonal and not interfere with each other Spiraling Poynting/linear momentum (and OAM) vectors! l=+1 l=+3 l= -4 17

18 Standard textbooks show that classical EM angular momentum is radiated all the way to infinity 18

angular momentum s = 1 Bo Thidé Orbital angular

19 Micromechanical action of SAM and OAM Particles of sizes 1 3 μm irradiated by SAM/OAM laser beams Spin angular momentum s = 1 Bo Thidé Orbital angular momentum l = 8 REAL Seminar, BTH, Ronneby, 23 January,

20 Very readable paper on POAM in astrophysics 20

$or diffractive hologram 21$

21 Imparting OAM onto an EM beam (laser, mm wave) with the help of a spiral plate or diffractive hologram 21

22 Breakthrough: Possible to generate and detect radio angular momentum with dipole/tripole antenna arrays! 22

23 Field vector sensing means total configurability Very good solar radio coronagraph! 23

24 Deep space radar requirements Courtesy Paul Rodrigues 24

25 Radio beam topology degrees of freedom Conventional linear momentum (Poynting) flux and E 25

simulation for s=1 and l=1 without any simplifying

26 Spin momentum ( photon spin current ) V and separation of SAM and OAM in a radio beam Full numerical simulation for s=1 and l=1 without any simplifying assumptions such as paraxial geometry, multipolar expansion etc. 26

27 LOIS has measured the photon spin current V in ionospheric radio signals since

28 Maxwell equations for the EM field Symmetry/group properties extremely useful 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 17 exact (in vacuo), plus an as yet unknown number of approximate, conservation laws [Ibragimov, 2008]. 28

29 The discrete reflection symmetry MIMO Maxwell equations multipath diversity Reflection, i.e. space inversion x x = -x is represented physically by the symmetry 29

30 Continuous symmetries in Maxwell's equations conserved electromagnetic quantities/observables Energy: Linear momentum: Angular momentum: 30

31 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! 31

32 First experimental verification of free-space information transfer using OAM degrees of freedom 32

33 Further experimental verification of free-space information transfer using OAM topological encoding 33

34 Pack EM beams with much more data by utilising more topological degrees of freedom 34

35 Hyperentangled SAM and OAM photon states break the linear-optics channel capacity threshold 35

36 Shannon s limit exceeded with OAM 36

37 OAM makes a new (rotational) frequency Ω available Interesting consequences for radio communications 37

38 Super-MIMO uses both multipath diversity and 2(l+1) SAM+OAM multistates 38

39 Radiation of power/linear momentum vs. radiation of angular momentum (MIMO limitations) Outside (but not inside) the source region, the fields can be accurately approximated by an expansion in spherical waves: The approximation (2) of approximation (1) is excellent for radiation of linear momentum (power, Poynting flux) but is completely wrong for radiation of angular momentum. The E R term excluded is the only term which gives rise to radiation of angular momentum! 39

40 The radio frequency spectrum is limited and expensive! Spiraling Poynting vectors! 40

41 Spin-off LOIS developments for space physics, astroparticle physics, and space communications Vector sensing radio on a chip, mm 2 at 4 grammes based on bare die components on silicon Vector radio system for detection of UHE neutrino induced radio pulses in the Antarctic ice 41

ET, we may wish to reconfigure our radio telescopes to look for encoding of the message via such subtle

42 New ideas new audiences. SETI? The investigation of new transmission modes by Thidé and Bergman hints that if we do find a signal from ET, we may wish to reconfigure our radio telescopes to look for encoding of the message via such subtle effects as orbital angular momentum. A simple signal may only be a cipher for a more complex message, and there may be more things in heaven and earth than even Maxwell had dreamt of 42

discussing, during a joint summer school on the Volga river, Russia 1997, the

43 Next challenge: Build a very-low-frequency LOFAR/LOIS on the far side of the Moon! Nobel Laureate Vitaly L. Ginzburg and B. T. discussing, during a joint summer school on the Volga river, Russia 1997, the possible new physics to be observed and studied with a radio observatory on the far side of the Moon. 43

44 Thank you for your attention...there may be more things in heaven and earth than even Maxwell had dreamt of 44

On the extraction of all information embedded in electromagnetic radiation

On the extraction of all information embedded in electromagnetic radiation On the extration of all information embedded in eletromagneti radiation Bo Thidé Swedish Institute of Spae Physis, IRF, Uppsala, Sweden LOIS Spae Centre, Växjö University, Sweden and the LOIS Photon Orbital