Possibly relevant, the disc itself has a very high refraction factor.
It is most puzzling to know how the disc manages to retain its shape, despite the non existence of any mechanical device left to artificially shape it that way.
We're just looking at something very very exotic. The effects can certainly be quantified, but the mechanism behind it is mysterous.
It seems to be able to generate its energy as it moves along, like a cascading chain reaction. Like, err... if it was a planar rift in subspace, with different dimensions and gravity somehow neglected, or something weird anyway, having a corresponding real space consequence such as the disk.
Now the completely superweird part, and I'm not sure about it, but it's like a feeling I get by looking at the vids. I notice that the intensity at the edge of the disc seems to remain the same. Small asteroids, be they next to the explosion point, or kilometers away, seem to be cut with the same amount of energy. Yet, the disc expands.