Rossi says that there are two sources of light produced by the QuarkX reactor. An internally generated light and a externally generated light.
The internally generated light source is due to the high-energy side-peak emission of exciton-polariton condensate in high density regime.
The experimental prediction that this theory expects is the production of the Mollow triplet in its spectral lines. This connect into the blue light seen in R. Mills experiments.
See the post below for more information on the Mollow triplet in spectral lines.