# Direct laser printing of chiral plasmonic nanojets by vortex beams

## TL;DR

This paper demonstrates that nanosecond laser vortex beams can create tunable chiral nanojets on plasmonic thin films, offering a new method for fabricating chiral nanostructures with controllable geometry and handedness.

## Contribution

First demonstration of nanosecond laser vortices producing chiral nanojets on plasmonic films with tunable size and chirality, advancing laser-based nanofabrication techniques.

## Key findings

- Chiral nanojets' height and aspect ratio are tunable via film thickness and substrate.
- Opposite vortex handedness produces nanojets twisted in opposite directions.
- Laser vortex parameters influence nanojet geometry and chirality.

## Abstract

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.