"Light-by-light scattering is a very rare phenomenon in which two photons – particles of light – interact, producing again a pair of photons."
This is the process that they observe (for the first time) whereas E144 observed the Breit-Wheeler process.
You can argue that this is too narrow a definition of light-by-light scattering but they have at least tried to make it self consistent...
Would have been nice if that info was featured somewhere in the article. I don't like to say it but this am I correct in saying that this article gives off the impression that this is an experimental first in terms of directly observing this photonic interaction?
making real Jedi saber
Projecting in the air without a screen could be a potential use.
On the other hand, it's true that a purely text-based medium like a comment doesn't have room for a lot of nuance. So for the sake of clarity, I will say that it was a good question. We should always look for ways to use new discoveries to our advantage. Let's just stick to things which are possible, like Dyson spheres, and leave the impossible for science fiction.
See also https://what-if.xkcd.com/1/.
My favorite part of this is looking at all the toasted skin on the fingertips in the video.
If of photon energy, then the device is clearly impossible -- you would need to use invisible (and harmful) gamma-rays for scattering.
If of energy density, it still may not be theoretically feasible. For instance, you cannot make monochromatic pulses arbitrarily short -- eventually they will become spread in frequency (more and more energy in higher and potentially harmful frequencies), such that the total dosage necessary to get the desired visible flux is too large. (some calculations would need to be made...)
Making them imperceptible, if that is even so important, has some challenges but not impossible (e.g. increasing resolution, lowering weight, or even adding devices to compensate its weight if the former is infeasible).
“Better dead than rouge?” Hm.
https://physicsworld.com/a/light-is-seen-to-scatter-off-ligh...
Link to paper from 1997: Positron Production in Multiphoton Light-by-Light Scattering
(published in Phys. Rev. Lett., Vol. 79, p. 1626 (1997).) http://www.slac.stanford.edu/exp/e144/ps/positron_slacpub.ps