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I have little knowledge about quantum phenomena, but I have read about super-conductivity and super-fluidity. The first involves zero resistance and the second involves zero viscosity. I suddenly thought of the following question:

Is there a corresponding quantum macroscopic phenomenon for attenuation of electromagnetic radiation? Namely is there a material under certain conditions that has zero attenuation of light at some wavelength?

Vacuum does not count, of course. If there is, is there a rough simplistic explanation? Or is such a phenomenon impossible, and why? Note that I am aware of the possibility of total transmission at Brewster's angle or total internal reflection at an optical boundary, but my question is about total transmission within the optical medium.

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    $\begingroup$ If you require that the medium has zero attenuation for all wavelengths, then the Kramers-Kronig relations imply that the index of refraction is 1 at all frequencies as well, i.e., the medium is indistinguishable from vacuum. But this isn't exactly a "simplistic" explanation, and I don't think it precludes zero attenuation at isolated frequency values. $\endgroup$ Jan 5, 2017 at 16:26
  • $\begingroup$ @MichaelSeifert: That's very interesting, and I'm glad I only asked for a material with total transmission at one wavelength. =) $\endgroup$
    – user21820
    Jan 5, 2017 at 16:29

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Beside passing light through vacuum--which would be an "obvious" solution--there are a few ways to create "super transmisivity", i.e. no optical attenuation when passing through point A to B.

1) Propagating light below the bandgap of a material: According to Kramers-Kronig relationship, index of refraction of a medium is 1 when a radiation field propagates far away from the atomic resonances present in the medium. This is more or less of a passive process, i.e. you cannot control the window of transparency, beside selecting different medium depending on the wavelength of the light.

2) Electromagnetically induced transparency (EIT): This is a very well understood and common experimental quantum optics phenomena, where through a use of pump beam one can prepare atoms in a very specific state such that the probe beam passes through the pump without any attenuation. If you were to switch the pump beam, the probe beam gets scattered by the atoms making the medium opaque. With EIT not only you can control the transparency window (frequency) of the medium but also make the medium opaque or transparent "at will"--some sort of an optical switch. In addition this process gives rise to an interesting phenomena called slow light, where one can slow down the speed of light. I am not sure (and don't remember the details) if people have achieve a unit transmission of the probe beam making it truly transparent. See: http://web.stanford.edu/group/harrisgroup/PAPERS/review.pdf

PS: The system does not let me comment (as I don't have enough reputation) thus typing my comment as an answer.

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  • $\begingroup$ I don't have sufficient knowledge to judge your answer, but your second point seems to me to be not an answer to my question, since I asked for a material that is transparent on a macroscopic scale, whereas the article you linked says that EIT cannot be used to achieve that at all. $\endgroup$
    – user21820
    Jan 7, 2017 at 3:47
  • $\begingroup$ For the first point, I can't tell whether it answers my question for the same reason because I literally want zero attenuation, not very small but still measurable attenuation. The fact that you say "far away from atomic resonance" implies that the attenuation is small but not zero, in which case it is not what I want. $\endgroup$
    – user21820
    Jan 7, 2017 at 3:53
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I dug this out for you,

http://www.jetp.ac.ru/cgi-bin/dn/e_073_02_0346.pdf

By this guy

http://www.itp.ac.ru/en/persons/falkovsky-leonid-aleksandrovich/

They were expecting Raleigh scattering should not occur below a certain frequency (related to band gap). This seemed to be true for low temp superconductors, but with high temp superconductors they got a linear response.

I'm sure some work must have been done on this since 1991, though. But this tells you it is a significant effect in Low temp superconductors.

Perhaps why there are so many papers on Raman (in-elastic) scattering, whose relatively small effects might in consequence be more easily measured. This effect, and probably some others, still prevent "total transmission", I think.

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