Chirality of laser-printed plasmonic nanoneedles tunable by tailoring spiral-shape pulses

摘要

We report on fabrication of Ag nanoneedles with tailored chirality via direct ns-laser printing with "structured" laser beams, zero-optical-angular momentum spiral-shaped beams with variable intensity profiles as well as the perfect optical vortex (POV) beams having fixed donut-shaped intensity pattern and variable topological charge. The chirality of the laser-printed nanoneedles was found to be efficiently tailored via optimization of the corresponding intensity pattern of the zero-OAM spiral-shaped beam, while the increase of the topological charge of the POV beam was shown to weakly affect the nanoneedle geometry. Our comparative study reveals the key role of the initial surface intensity (temperature) distribution driving the helical movement of the transiently molten metal and directing formation of the nanoneedles with pronounced chirality on the surface of the noble-metal films. The obtained results pave the way toward realization of easy-to-implement scalable technology for the direct laser printing of plasmonic nanoneedles with pronounced and tailored chirality suited for various nanophotonic, chemical and biosensing applications.