For reasons that have never been satisfactorily explained to me, the Glass Map (AKA an Abbe Diagram) has the Abbe number of the glass (the V-number, or dispersion index, a measure of how much the index of refraction changes over the visible range) running from larger to smaller numbers along the x-axis, while the indices of refraction increase from bottom to top along the y-axis in the usual fashion. I suspect people just like the way the chart looks with the x-axis reversed. Schott isn’t the only company that does this; every glass manufacturer has aGlass Map that looks like this:
You could in principle get some sort of manifestation of the photon field with a structure size larger than the observable Universe, but that manifestation, whatever it was, wouldn’t be a wave.