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Light redirecting field.

  1. Dec 9, 2004 #1
    Is it possible to have (some sort of) a FIELD that could be projected into some space to redirect light into desirable direction.
     
  2. jcsd
  3. Dec 9, 2004 #2

    Photonic crystals are constructed and used for this purpose. Crystals are a bunch of atoms sitting on some lattice...Ofcourse like in the case of semi-conductors, electrons moving in a periodic potential will have certain energy-values that they cannot exhibit...These forbidden energy-values form the socalled band-gap. Now suppose that in the crystal, you remove some unit cells in order to make a "corridor" through that crystal. If you are sure that the frequency of an incident EM-wave is equal to some frequency IN the band-gap, then this radiation will not interact with the crystal and it will propagate through the corridor that we made...

    By this principle you have constructed a conductor for EM-radiation...

    This system is used in several engineering fields....(optical communication etc...)


    regards
    marlon
     
  4. Dec 15, 2004 #3
    I've read some texts on the Internet about photonic crystals (after you've drawn my atention to it), but I never succeded to make myself realise some really strict practical use for it.

    Are you sure this has to do with what I've asked?

    This is what I've meant:
    Imagine that you have some relatively small thing (an aparature), and when you press a button on it a field is being projected infront of that thing (completely free in space, not surrounded by aparature); and when you look through that field it feels like you're looking thorough a lense, so you can use it as a magnifying glass. (that would be a practical use for what I had in mind)
     
  5. Dec 15, 2004 #4
    SAZAR, you seem to be describing an electron microscope, in which electrons are indeed deflected through such EM lenses.

    For photons however, matter is practically necessary. EM fields have not been observed to deflect other EM fields independently of matter.

    I have asked a similar question in the General Relativity forum a while ago, and the replies indicated that if such an effect could be observed, the fields involved would need to have stellar proportions. GR seems to predict some kind of interaction though.
     
    Last edited by a moderator: Dec 15, 2004
  6. Dec 17, 2004 #5
    I believe magnetic fields can change the plane of polarisation of light, but I'm not too sure about changing it's momentum of angular momentum(direction). Hmmm .. gravity can change these things though. Light is deflected in gravitational fields.
     
  7. Dec 17, 2004 #6

    ZapperZ

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    Where did you read that?!

    If this is true, we would not have needed all those complicated optics to generate different types of polarization of the light generated out of a synchrotron.

    Zz.
     
  8. Dec 21, 2004 #7
    Hmm...
    ...Let's now put aside geometrical explanation of how lenses bend light, and let's focus on WHAT (AND HOW) inside of matter actually does the job, and also how does all of that affect different vawelenghts to bend at different angles in prisms. What atoms of the matter lense consists of do to light in order to change its direction. (does temperature change lightbending properties beyond those produced by changed shape of the object (by expanding) which makes up lense)

    Since atoms are made of subatomic particles, and subatomic particles are made of quantum particles, and a photon is also of quantum particles, then what interaction between those particles is in question here, and can that interaction be mimiced to create an effect I described before?
     
  9. Dec 21, 2004 #8

    ZapperZ

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    Again, I hate to keep repeating the same thing over and over and over again... But I suggest you do a search on "optical conductivity" on here. There have been several threads in which I explained the fundamentals of optical conduction (and reflection) in solids, ranging from metallic materials all the way to dielectric/insulators. I want to dispel the fallacy that this isn't a studied area. Optical transport in matter is a huge field in condensed matter physics, so much so that it is a major technique in the study of materials properties.

    Zz.
     
  10. Dec 22, 2004 #9
    In matter (glass), this is the Faraday effect.

    In vacuum, this has not been observed, although some people looked very hard for it. It would be a telltale signature of a new particle, the axion. Melissinos tried this with long strong superconducting magnets and a laser beam, and found a new upper boundary.
     
  11. Dec 29, 2004 #10
    Isn't it more easier to write down some URL links leading to those pages?
     
  12. Dec 29, 2004 #11

    ZapperZ

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    Not if the accompanying point to be made is to have people FIRST do a search on here and see if things have been discussed ad nauseum already. This is before a separate point being that what one thinks to be "new" or "unresearched" is in fact well-known and well-studied.

    Zz.
     
  13. Dec 29, 2004 #12
    No. Can't you see - you actually made the very same mistake you've been complaining about: you said what you said like you think that I was asking THAT question (about what redirects light inside matter) just for the sake of that question itself (you said: "This is before a separate point being that what one thinks to be "new" or "unresearched" is in fact well-known and well-studied." - those words imply what I've just said - you don't know what is my point).

    You, actually didn't see that the question I asked is in the CONTEXT of the main theme - how to practicaly make light redirecting field to have an effect I described. - It's like you "didn't do the homework" on what I've said in my first two posts either, so you don't know what I'm actually asking.

    The main part in that post of mine was: "can that interaction be mimiced to create an effect I described before?"

    If you KNOW that it can't be mimiced, then say so, and explain or point toward an explanation. I just asked a simple qustion - and that's what this forum (ACTUALLY) is about (just that) - those people who know things show the other ones what to look for instead them looking for it by themselves. Why should anyone discuss something he already knows - and there are all sorts of different ways to get to know things...
     
  14. Dec 29, 2004 #13

    ZapperZ

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    You are correct. I WAS NOT addressing your ORIGINAL question of the thread. It wasn't what I intended to do in the first place! What I was trying to do is correct what you said HERE:

    Now correct me if I'm wrong, but you are describing how light of different wavelengths "bends" at different angle in prisms, etc. In other words, you are asking about the issue of optical conductivity in solids! Now tell me where I misinterpreted this? I am NOT addressing your original question, of which I reserved my judgement of. However, once you try to somehow equate light transport in vacuum with that in solids, then someone should point out to you that optical conductivity is a well-studied area of condensed matter physics. The conduction electrons, plasmon states, phonon modes, etc, ALL conspire to give a material its inherent ability to allow or attenuate light propagation and "bending".

    If you think what I'm trying to tell you is a waste of your (and my) time and is irrelevant to what you want, then you're more than welcome to ignore it.

    Zz.
     
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