Nice! I worked on something similar as an undergrad project years ago, setting up beams with different orbital angular momentum characteristics. Was a lot fun working in the lab. Sadly I didn’t have the focus/grit to finish writing a paper (sorry Dr. Singh). Side note, this was in 2007 and the folks in our optics lab would check the location of beams by grabbing from the stacks of ancient punchcards lying around and waving them next to the apparatus.

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.

Can't extract meaning past the third or fourth line, but just as an idle curiosity: isn't a vortex the product of interaction between the particles? Are photons interacting with each other?

I can't speak on the subject, but I just want to say I really enjoyed the Star-Trek-esque language (:

  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!"