This paper has a pretty similar setup, but adds a spatial light modulator (like a DLP projector that can control phase as well as brightness).
What is wild to me is that the researchers here are able to create a beam where the angular moment changes as you move away.
Plus the really cool spiral patterns.
Here, we introduce optical rotatum, a behavior of light in which
an optical vortex beam experiences a quadratic chirp in its orbital
angular momentum along the optical path. We show that such an adiabatic
deformation of topology is associated with the accumulation of a Gouy
phase factor, which, in turn, perturbs the propagation constant (spatial
frequency) of the beam.
"Captain, if we can't reduce the adiabadic deformation of the Gouy phase factor, we'll never escape this optical vortex beam!"* Somebody’s name or,
* Exactly what they say on the tin
Right? The language of physics has some false-friends in English.