alt Hacker NewsAt high energies I think you could point two at a spot in space and get antimatter where the beams cross (also matter, and then an explosion... see the Breit-Wheeler process).
We have a hard enough time building shipping-container sized devices that reflect extreme ultraviolet though... so I think a handheld gamma ray laser is off the table for this century.
But, is there any property of that point in space you could measure by how exactly this occurs?
I.e. could you make some kind of massive confocal telescope using this effect in place of regular multi-photon fluorescence, to measure a 3D volume of space?