These are figures from the paper linked above, which is a bit dated.
The "emitter" is the Fe2O3:K catalyst, which is directly heated by a current passed through the tube holding it. Hydrogen diffuses through the heated catalyst which forms a loosely bound "cloud" of Rydberg matter and ultra-dense hydrogen material around it, and is here probed with the laser at a small distance from its surface.
The ultra-dense hydrogen produced also falls on the metallic foil/holder assembly that can be seen in the photo, as if it were a liquid. In newer papers the laser would be typically focused there.