What isn't clear to me here is where this weapon came from? I know that they've been experimenting with a creator artifact, I didn't think they had one that was mobile...
Its an adaption of the drive from the alien/creator ship. It uses a tweaked jump field to convert matter to energy directly, and in this case the bulk of the energy is in photons. The original drive had a dispersed 'exhaust' while the weapon keeps it in a tight beam.
I was going to say, that was one heck of a laser for a small ACV.
Image a light source that's measured in tons of thrust?