  Donut-shaped laser radiation, carrying orbital angular momentum, namely
optical vortex, recently was shown to provide vectorial mass transfer, twisting
transiently molten material and producing chiral micro-scale structures on
surfaces of different bulk materials upon their resolidification. In this
paper, we show for the first time that nanosecond laser vortices can produce
chiral nanoneedles (nanojets) of variable size on thin films of such plasmonic
materials, as silver and gold films, covering thermally insulating substrates.
Main geometric parameters of the produced chiral nanojets, such as height and
aspect ratio, were shown to be tunable in a wide range by varying metal film
thickness, supporting substrates, and the optical size of the vortex beam.
Donut-shaped vortex nanosecond laser pulses, carrying two vortices with
opposite handedness, were demonstrated to produce two chiral nanojets twisted
in opposite directions. The results provide new important insights into
fundamental physics of the vectorial laser-beam assisted mass transfer in metal
films and demonstrate the great potential of this technique for fast
easy-to-implement fabrication of chiral plasmonic nanostructures.
