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Without reducing the energy more than necessary due to the frequency decrease? And if this happens/works, is there an index of such materials and their optic properties?

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  • $\begingroup$ Doppler shift from a (first surface dielectric) mirror. $\endgroup$
    – Uncle Al
    Feb 6, 2014 at 19:25

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There is a physical process called Raman scattering that produces the effect that you describe. Part of the photon energy is transferred to vibration of bonds in the material, and the frequency of scattered light is thus reduced by the frequency of of these vibrations. Crystals work best because they have lots of equivalent bonds that vibrate at the same frequency.

The main problem is that this process is thousand times less efficient than usual scattering that preserves the frequency, so a) shifted light will be obscured by regular scattering and b) it will be very weak. With a powerful monochromatic light source, like laser, one can see Raman scattering using a color filter that blocks the laser light. By measuring the frequency shift it is possible to identify the surface structure of the material, so Raman scattering is often used in diagnostics.

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  • $\begingroup$ why do I have the impression that the OP is asking the complement to this? I think as the question is phrased the shape of the incoming frequency should be shifted by a constant amount and not one frequency come out from many. $\endgroup$
    – anna v
    Nov 8, 2013 at 14:34
  • $\begingroup$ @annav I thought that I also understood the question this way: is there a process that shifts every frequency of incoming light by the same amount. And my answer is - Raman shift does exactly that, albeit with a low efficiency. $\endgroup$
    – gigacyan
    Nov 8, 2013 at 19:05
  • $\begingroup$ I believe the restriction is to "all light reflected off it", not some. And strictly speaking, Raman scattering operates on EM radiant energy; not on "light" which is a psychophysical response of the human eye to some EM radiations. $\endgroup$
    – user26165
    Nov 9, 2013 at 1:28
  • $\begingroup$ @gigacyan suppose you have a frequency distribution . Will the shape of that distribution be the same but at lower h*nu? $\endgroup$
    – anna v
    Nov 9, 2013 at 6:35
  • $\begingroup$ @annav Generally - yes, but whether you would see it depends on the frequency distribution of light. If it is narrowband (less than, say, 50 nm), then Raman-shifted light is spectrally separated. For a broadband light you would not be able to see the shifted spectrum, but it would still be there. $\endgroup$
    – gigacyan
    Nov 9, 2013 at 13:35

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