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orbital angular momentum of light (OAM)

Discussion in 'Electronic Design' started by Jamie M, Aug 3, 2013.

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  1. Jamie M

    Jamie M Guest

    Hi,

    I read an article today about bouncing light off of a spinning object
    and then detecting its rotation rate by measuring the reflected lights
    orbital angular momentum. I had mentioned earlier that you could
    produce light with orbital angular momentum by rotating an LED or laser
    at a high speed, and I think this is the same effect but in reverse.

    "Researchers find way to measure speed of spinning object using light's
    orbital angular momentum"

    http://phys.org/news/2013-08-orbital-angular-momentum.html

    Also here's a new question! Can light with orbital angular momentum
    cause an object to rotate, and how does that relate to the scale of OAM
    of light going from zero OAM to infinite OAM?

    cheers,
    Jamie
     
  2. Glenn

    Glenn Guest

    Hi Jamie

    Somemany have written an article here:

    https://en.wikipedia.org/wiki/Orbital_angular_momentum_of_light

    It is incredible that no one has thought of that before.


    Nov 1, 2012, physicsworld.com: Spooky action with twisted beams:
    http://physicsworld.com/cws/article/news/2012/nov/01/spooky-action-with-twisted-beams
    Quote: "...
    Using this technique, Zeilinger and co-workers found they could obtain
    differences in quantum number as high as 600 (in other words l = +300 on
    one photon and l = –300 on the other). Lapkiewicz points out that there
    is, in theory, no upper limit to a photon's l value, which suggests that
    a photon – a quantum object – could acquire as much OAM as a macroscopic
    object, leading to what he calls a "tension between the quantum and
    classical worlds"
    ...."



    Oct 19, 2012, physicsworld.com: Chip puts a twist on light:
    http://physicsworld.com/cws/article/news/2012/oct/19/chip-puts-a-twist-on-light
    Quote: "...
    Indeed, he says that they aim to produce devices that can emit different
    OAM values at the same time. This, he claims, could enhance
    telecommunication bandwidth, by increasing the number of channels
    available, and boost the power of quantum computers – devices, still
    under development, that promise much faster data crunching by processing
    multiple quantum states simultaneously. "Currently, quantum computers
    rely on electron spin or photon spin, which only have two states,
    whereas OAM has many states," he explains
    ...."


    25 June 2012, BBC 'Twisted light' carries 2.5 terabits of data per
    second:
    http://www.bbc.co.uk/news/science-environment-18551284
    Quote: "...
    Recent work suggests that the trick could vastly boost the data-carrying
    capacity in wi-fi and optical fibres
    ....
    The idea is not to create light waves wiggling in different directions
    but rather with different amounts of twist, like screws with different
    numbers of threads
    ...."

    University of Southern California (2013, June 27). Breakthrough in
    Internet bandwidth: New fiber optic technology could ease Internet
    congestion, video streaming. ScienceDaily:
    Quote: "...
    the technology centers on donut-shaped laser light beams called optical
    vortices, in which the light twists like a tornado as it moves along the
    beam path, rather than in a straight line
    ....
    Unlike in conventional fibers, OAM modes in these specially designed
    fibers can carry data streams across an optical fiber while remaining
    separate at the receiving end
    ...."

    /Glenn
     
  3. Glenn

    Glenn Guest

    (answer to sci.electronics.design )

    A radioamateur might have this question:

    If a radio antenna radiate OAM-8 waves, how does the wavefront then look
    like?

    -

    I radio beacon might radiate in angles equal the OAM in one frequency
    only; e.g.:
    0° = OAM-0
    1° = OAM-1
    ....
    180° = OAM-180
    ....
    359° = OAM-359

    or

    0° = OAM-0
    0.1° = OAM-1
    1° = OAM-10
    ....
    180° = OAM-1800
    ....
    359.9° = OAM-3599

    I do not know how the antenna system might look like - or if it even
    feasible.

    With 2 or more OAM enabled radio beacons an approximate position on
    earth can be defined immediately.

    -

    If that is possible, a linear polarized wave can be used for longwave,
    shortwave time signal that will also pinpoint where you are on earth. It
    might be used for a new GPS, that can instantly make a approximate
    position in 3D around earth or other planets.

    https://en.wikipedia.org/wiki/Time_signal#Radio_time_sources

    /Glenn
     
  4. Glenn

    Glenn Guest

    (answer to sci.electronics.design )

    ....

    Silly me, the angle encoding should of cause use gray encoding:
    http://en.wikipedia.org/wiki/Rotary_encoder#Gray_encoding
    Quote: "...
    To avoid the above problem, Gray encoding is used. This is a system of
    binary counting in which adjacent codes differ in only one position. For
    the three-contact example given above, the Gray-coded version would be
    as follows.
    ...."

    /Glenn
     
  5. Glenn

    Glenn Guest

    In what way?

    http://en.wikipedia.org/wiki/Anton_Zeilinger
    Quote: "...
    Anton Zeilinger’s achievements have been most succinctly described in
    his citation for the Isaac Newton Medal of the Institute of Physics
    (UK): “For his pioneering conceptual and experimental contributions to
    the foundations of quantum physics, which have become the cornerstone
    for the rapidly-evolving field of quantum information.” He is a pioneer
    in the field of quantum information and of the foundations of quantum
    mechanics. He realized many important quantum information protocols for
    the first time, including quantum teleportation, entanglement swapping,
    dense coding, entanglement-based quantum cryptography, one-way quantum
    computation and blind quantum computation. In addition, he made many
    important contributions to the conceptual and experimental foundations
    of quantum mechanics, particularly in the areas of quantum entanglement
    and macroscopic quantum mechanics.
    ...."


    Science 2 November 2012:
    Vol. 338 no. 6107 pp. 640-643
    DOI: 10.1126/science.1227193
    Quantum Entanglement of High Angular Momenta
    Robert Fickler
    Radek Lapkiewicz
    William N. Plick
    Mario Krenn
    Christoph Schaeff
    Sven Ramelow
    Anton Zeilinger
    http://www.sciencemag.org/lookup/doi/10.1126/science.1227193
    http://www.sciencemag.org/content/338/6107/640.full
    Quote: "...
    In our experiment, polarization-entangled photon pairs (uncorrected
    average visibility 97.99 ± 0.03%) at 810 nm were created using a type II
    nonlinear crystal in a Sagnac-type configuration (26, 27).
    ....
    The highest value of OAM per single photon where strong correlations
    were still measurable was l = ±300 for both photons (Fig. 3C).
    ....
    When we transfer one photon to high OAM values and keep the other in its
    polarization state, the pair can be used to remotely measure an angular
    rotation with a precision that is increased by a factor l relative to
    the situation when only polarization-entangled photon pairs are used
    (Fig. 4) (22).
    ...."


    /Glenn
     
  6. Phil Hobbs

    Phil Hobbs Guest

    The black body formula, abundantly confirmed by experiment, relies on an
    exhaustive enumeration of all the available states of the EM field, and
    they don't include the orbital angular momentum states.

    The equipartition theorem requires that in thermodynamic equilibrium,
    all accessible states have the occupation number 1/(1+exp(h*nu/(k*T))).
    If there were really all those extra states, black bodies would
    radiate very much more intensely than they do.

    So either (a) it's wrong, or (b) it's another Ultraviolet Catastrophe.
    My bet is on (a). The quantum optics people have been ludicrously wrong
    before now, e.g. the once firmly held claim that light from two
    different sources could never produce interference fringes.

    Cheers

    Phil Hobbs



    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC
    Optics, Electro-optics, Photonics, Analog Electronics

    160 North State Road #203
    Briarcliff Manor NY 10510 USA
    +1 845 480 2058

    hobbs at electrooptical dot net
    http://electrooptical.net
     
  7. Jamie M

    Jamie M Guest

    Hi,

    I think OAM and the relativistic hall effect could give a physical
    description of E=mc^2 and physically describe the translation between
    energy and matter maybe. Maybe matter is light with significant OAM,
    and the relativistic hall effect asymmetry of its motion causes it to
    curve into a toroid shape or other shapes that can be self sustaining.

    cheers,
    Jamie
     
  8. Jamie M

    Jamie M Guest

    Hi Jan,

    Thanks for clearing that up!

    cheers,
    Jamie
     
  9. Guest

    You mean m = 8? Look here:

    http://en.wikipedia.org/wiki/File:Helix_oam.png

    and do the logical extrapolation.
    Here's the general idea:

    http://iopscience.iop.org/1367-2630/14/3/033001/article

    See figure A4 and table A2, about 2/3 of the way down the page. The sidelobes aren't shown but it looks to me like they'll be, er, messy.

    In a Q&A forum I can't find right now I asked Thidé if a piezo element inserted in the gap in the dish could real-time modulate the value of m, and he said "I don't know, we will have to try it".


    Mark L. Fergerson
     
  10. Glenn

    Glenn Guest

    (answer to sci.electronics.design )


    More about OAM - it is useful:


    Aug 5, 2013, Rotational Doppler shift spotted in twisted light
    http://physicsworld.com/cws/article...tional-doppler-shift-spotted-in-twisted-light
    "...
    The team fired two beams of light carrying orbital angular momentum at a
    rotating surface and showed that the resulting interference pattern in
    the reflected light is related to the surface's angular velocity.
    ....
    The frequency of the scattered beam with orbital angular momentum in the
    same direction as the surface is raised slightly (blue-shifted), while
    the frequency of the beam with angular momentum in the opposite
    direction is lowered (red-shifted) by the same amount (see figure).
    ....
    "I think it's quite unexpected and might be surprising that you have
    this Doppler effect even though there is nothing that is moving closer
    or farther from the detector," he says. "Of course, you can understand
    it with hindsight by reasoning about the effect, but without this work
    you would not expect it to occur."
    ...."

    /Glenn
     
  11. Jamie M

    Jamie M Guest


    Hi Phil,

    Cool, I read about it - sounds feasible kind of, "electron liquid" with
    quantized states appearing out of "no where", really interesting!
    Sounds like a new state of matter being created. I guess you are using
    graphene to avoid the low temperature requirements? (I was reading that
    graphene may not need the low temperatures for the effect to occur).

    I have a feeling it is a good way to learn about electrons by studying
    this field! Pretty much unexplained though as I have read that the fine
    structure constant value is still an unsolved mystery.

    cheers,
    Jamie
     
  12. Jamie M

    Jamie M Guest

    I was reading some more about the fine structure constant, and
    apparently it isn't actually a constant but will changed based on
    conditions, ie from wikipedia:

    http://en.wikipedia.org/wiki/Fine-structure_constant

    "While the fine-structure constant is known to approach 1/128 at
    interaction energies above 80 GeV"

    The mystery of the fine structure constant has been that it's value is
    in a narrow range that allows for matter to exist, but this is looking
    at it backwards, since if the fine structure constant can change (as
    shown by the change in its value at 80GeV), then obviously it is
    changing based on the conditions, so it will take on a value that
    matches the conditions. So it's a variable.

    cheers,
    Jamie
     
  13. Phil Hobbs

    Phil Hobbs Guest

    No, it's using low-TC SQUID ICs. Until my quantum mechanics is back up
    to speed, I'm just going to be kibitzing and help solve implementation
    problems. It'll be nice to have colleagues again.

    Anyons for tennis? ;)

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC
    Optics, Electro-optics, Photonics, Analog Electronics

    160 North State Road #203
    Briarcliff Manor NY 10510

    hobbs at electrooptical dot net
    http://electrooptical.net
     
  14. Jamie M

    Jamie M Guest

    Hi,

    Thats the explanation I read before, really bad explanation.

    cheers,
    Jamie
     
  15. Jeroen

    Jeroen Guest


    Since the fine structure constant is basically the ratio of the
    impedance of free space and the quantum hall resistance, it contains
    just c, e, u_o and h. Which of those would be variable? Oh, yes,
    there's a factor of two in there too. That must be it. ;-)

    Jeroen Belleman
     
  16. Jamie M

    Jamie M Guest

    Hi,

    Actually probably all of them except the factor of two :)

    cheers,
    Jamie
     
  17. Glenn

    Glenn Guest

    FYI:


    Jul 2, 2013, Twisted light carries data over 1 km in optical fibre:
    http://physicsworld.com/cws/article...light-carries-data-over-1-km-in-optical-fibre
    Quote: "…
    A new type of optical fibre that can carry "twisted" light over long
    distances has been developed by researchers in the US, Israel and Denmark.

    According to Ramachandran, who led the development of the fibre, the new
    system is designed so that the phase velocities of the OAM modes are
    different. This minimizes the probability of coupling between modes as
    the signals propagate along the fibre.

    This fibre is designed to carry four distinct modes – two zero-OAM modes
    that propagate in the inner circular core and two OAM modes that
    propagate in the outer ring. [PS: in the same kernel]

    Development of the system that encodes and decodes the OAM pulses was
    led by Willner at USC. Dubbed OAM mode-division multiplexing (OAM-MDM),
    the system encoded data into four separate channels. These are defined
    in terms of the OAM (0 or 1) and circular polarization (–1 or 1) of the
    light. Using just these four modes, the team was able to transmit data
    over a 1.1 km fibre at a rate of 400 Gbit/s.

    The system was also able to reproduce each quartet of OAM modes at 10
    different wavelengths of light – a technique called wavelength-division
    multiplexing (WDM). This boosted the transmission rate to 1.6 Tbit/s –
    the equivalent of transmitting eight Blu-ray discs every second. While
    such data rates are routinely achieved by commercial WDM systems, this
    is the first time that OAM-based transmission has been achieved over
    distances greater than a metre.
    …"

    ( New Optical Fiber Puts a Twist on Data Transmission:
    http://www.photonics.com/Article.aspx?AID=54269 )

    -

    Science 28 June 2013: Terabit-Scale Orbital Angular Momentum Mode
    Division Multiplexing in Fibers:
    http://www.sciencemag.org/content/340/6140/1545.abstract
    Citat: "…
    Internet data traffic capacity is rapidly reaching limits imposed by
    optical fiber nonlinear effects. Having almost exhausted available
    degrees of freedom to orthogonally multiplex data, the possibility is
    now being explored of using spatial modes of fibers to enhance data
    capacity. We demonstrate the viability of using the orbital angular
    momentum (OAM) of light to create orthogonal, spatially distinct streams
    of data-transmitting channels that are multiplexed in a single fiber.
    Over 1.1 kilometers of a specially designed optical fiber that minimizes
    mode coupling, we achieved 400-gigabits-per-second data transmission
    using four angular momentum modes at a single wavelength, and 1.6
    terabits per second using two OAM modes over 10 wavelengths. These
    demonstrations suggest that OAM could provide an additional degree of
    freedom for data multiplexing in future fiber networks.
    …"

    -

    Nature Photonics 6, 420–422 (2012), Optical communications: Multiplexing
    twisted light:
    http://www.nature.com/nphoton/journal/v6/n7/full/nphoton.2012.154.html?WT.ec_id=NPHOTON-201207

    -

    September 16-20, 2012, Orbital Angular Momentum (OAM) Based Mode
    Division Multiplexing (MDM) over a Km-length Fiber:
    http://www.opticsinfobase.org/abstract.cfm?URI=ECEOC-2012-Th.3.C.6
    Citat: "…
    Abstract We demonstrate the first MDM scheme using OAM states over
    1.1-km of fiber. This is enabled by a SLM-based Mux/Demux setup, and a
    fiber designed to propagate multiple OAM modes over km lengths. We
    confirm low crosstalk (<-14.8dB) and multipath interference (<-19.7dB)
    of this scheme by transmitting 400Gb/s QPSK data at 1550nm without MIMO
    processing.
    …"

    br,

    Glenn
     
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