I pulled the paper at work.
They are using Using water ripples ringing around a droplet to create a symmetrical array of phonons to cause a minute , but highly controllable frequency shift of the pump laser light.
All it does is impart a controlled Raman or Brillioun shift to the incoming light. Which is cool if your doing certain types of spectroscopy in a lab. However the wavelength shifts are very small, on the order of a few Kilohertz to maybe .001 nanometer. Very useful in ultrafine spectroscopy, perhaps, but otherwise nothing to write home about at LPF.
Sad, the Journo's did not have a physicist around to tell them this was a non-issue for most of their readers.
Its not really a " water " laser, its a tunable frequency shifting assembly that emits coherent light in minute amounts.
A very neat technique, that only a few dozen labs in the world can replicate or explore right now.
Steve