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B Superconductivity for light beams?

  1. Jun 2, 2017 #1
    As is well known, superconductivity is described as a property of zero-resistance for electrical current, however, I want to know, is there any material with superconductivity for light beams, in which the light beams can propagate with no losses?
     
  2. jcsd
  3. Jun 3, 2017 #2

    davenn

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    do you understand what an electric current is and how it propagates in a conductor ?

    do you understand what light is and how it propagates ?

    when you answer those and understand the difference, you will discover a flaw in your idea/thought :wink:


    Dave
     
  4. Jun 3, 2017 #3
    I think, it can be re-framed as "Do we know about any substance through which light can travel through without any attenuation?"
    To which a good enough answer would be optical fiber. The point is light, being light, can die down as it progresses through a media, where as the current we think of as a flow of charge doesn't "die down" in a typical closed circuit. However, resistor can be treated as a dissipating agent just as easily as the opacity of a material for light.
     
    Last edited: Jun 3, 2017
  5. Jun 3, 2017 #4

    davenn

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    please keep your derogatory comments to yourself !!

    I am trying to see what understanding the OP has on the topic without giving direct answers
    We here at PF try to get people to think for themselves, it aides in the learning process :smile:
     
  6. Jun 3, 2017 #5
    Point taken, that makes sense, the more I think about it.
     
  7. Jun 3, 2017 #6

    davenn

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    the problem is, we have no idea what the OP is thinking. So we need to get them to tell us their understanding and also to
    more specifically define what they are wanting to know , which at the moment, from their opening post, is a little vague :smile:

    Lets see how they respond


    Dave
     
  8. Jun 3, 2017 #7
    Thank Dave and Ranvir for kind replies. Ranvir tells what I want to know. I am searching for a kind of material that won't introduce losses when the light propagates in, whatever the principle is. I have considered the optical fiber, but the losses will increase with the distance increasing. Thought of superconductivity, I asked the question. So, is there any solution, even in theory?
     
  9. Jun 3, 2017 #8

    davenn

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    nothing that I am aware of .... all mediums that will support the transmission of light will have losses

    again I ask, since you didn't answer my questions ...

    do you understand what light is and how it is different to an electric current ?

    Dave
     
  10. Jun 4, 2017 #9
    As I know, light is essentially a kind of electro-magnetic wave, it can propagates in vacuum with a speed of ##c##. It propagates in a medium with a speed of ##c/n##, ""n"" is the refractive index of medium.
    While electric current is a field formed by the moving of electrons, it also propagates with ##c##, the difference to light is that it need a medium to propagate in. The moving of electrons will stopped or blocked by something called resistance and the corresponding current will decrease. At a very low temperature, some materials can have a property of zero resistance, which is called superconductivity.
     
  11. Jun 4, 2017 #10

    davenn

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    this bit needs revised a bit :smile:

    The electric field exists regardless of it the electron ( charge carrier) is moving or not.
    That is, a single motionless charged particle electron/proton already has an electric field around it

    http://www.physicsclassroom.com/class/circuits/Lesson-1/Electric-Field-and-the-Movement-of-Charge

    electrons don't move at the speed of light they actually move at a slow speed in a conductor ~ 1mm / sec give or take a bit depending of a few variables --- google electron drift

    The electric field propagates at less than the speed of light in anything other than a vacuum, how much less depends on the conductor, insulation type etc
    The electric filed will also happily propagate in a vacuum ... It does not need a medium. Same for the magnetic field

    what I am aiming towards with these Q's and comments to you is that there is a very different process between the movement/propagation of an electric charge ... CONDUCTION and the movement/propagation of light ( an electromagnetic field) .... RADIATION
    Light doesn't conduct ( well I have never seen it written anywhere that it does), therefore talking about superconductivity for light is meaningless


    Dave
     
    Last edited: Jun 4, 2017
  12. Jun 5, 2017 #11

    ZapperZ

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    The words you use are at fault here.

    What you want is a "lossless medium" for light propagation (presumably over a range of frequencies). You should use that phrase rather than invoking "superconductivity", because "superconductivity" involves a number of consequences and effects, NOT just "zero resistance".

    Zz.
     
  13. Jun 5, 2017 #12

    f95toli

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    But only or DC; the losses in a superconductors increase as you increase the frequency. In fact, at frequencies above a few hundred GHz (which is taking you close to the far infrared; i.e. "light") the losses in superconductors can exceed those of normal metals at the same temperature.
     
  14. Jun 5, 2017 #13

    berkeman

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    This is not true. Optical fiber may be low loss, but most certainly is not zero loss. Just look at the need for optical repeaters in fiberoptic trans-Atlantic communication cables on the ocean floor...

    https://en.wikipedia.org/wiki/Submarine_communications_cable
     
  15. Jun 5, 2017 #14
    Thank you for your detail interpretation. However, I am still a little confused. Both electrical current and light radiation, are propagating with the help of motion of electro-magnetic field and their speeds are both near the light speed. So in the concept of "field", what's the essential difference between them? Are they interpreted by classical Maxwell electro-magnetic equation?
     
  16. Jun 5, 2017 #15

    davenn

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    but the electric current ISNT moving at the speed of light !
    did you do as I suggested and google electron drift ?
     
  17. Jun 6, 2017 #16
    Yes, I have followed your suggestion and I know that the velocity of electron drift is very slow. But the foundation of electrical field is very fast (nearly the speed of light), in other words, the transmission speed of information carried by electrical field is very fast. See https://en.wikipedia.org/wiki/Speed_of_electricity. So my point is why the electrical field of electrical current can't be seen as the light current, since they are both electromagnetic field in nature?
     
  18. Jun 6, 2017 #17
    Thanks, I will follow up on this
     
  19. Jun 6, 2017 #18

    davenn

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    because conductivity ( superconductivity) deals with current, the movement of charge carriers, NOT electric or EM fields
    there is no such thing as "light current"
     
  20. Jun 6, 2017 #19
    Thank you for your kind help. I seem to get the point: superconductivity is a behavior of charge carriers and happens when the resistance of their moving is zero. The propagation of light don't need the help of the moving of something, so there is no corresponding resistance and thus superconductivity.
     
  21. Jun 6, 2017 #20
    I'm a bit surprised to not see the obvious answer here: the most lossless medium for current and radiation is ... space.
     
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