Abstract
Laser irradiation of various materials including metals, polymers, and semiconductors with vortex beams was previously shown to “twist” transiently molten matter providing the direct easy-to-implement way to obtain chiral surface relief. Specifically for metals, this effect was attributed to transfer of an orbital angular momentum (OAM) carried by a vortex beam. In this Letter, we report the formation of twisted metallic nanoneedles on surfaces of silver and gold films under their irradiation by a zero-OAM laser beam with a spiral-shaped intensity distribution. Our comparative experiments clearly demonstrate, for the first time to the best of our knowledge, that the formation of the chiral nanoneedles on the noble-metal films is mainly governed by the temperature-gradient-induced chiral thermocapillary mass transfer, rather than by OAM-driven rotation of the molten matter.
© 2017 Optical Society of America
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