Speaker: Dr Nafia Rahaman, Senior Postdoc, Quantum Nanophysics Group, University of Vienna, Austria

Abstract:
The synthesis of nanoparticles, characterized by precise size and shape control, has posed a significant challenge in the realms of both nanotechnology and the growing field of levitated optomechanics. In this study, we unveil a novel approach encompassing the fabrication, launch, and detection of nanoparticles in both gaseous and vacuum environments. Our methodology involves the utilization of a highly focused ultra-fast laser beam with substantial intensity yet minimal energy to liquefy, form, and release individual particles during each optical pulse. Surface tension plays a crucial role in facilitating the formation of spherical particles from molten droplets, allowing for the manipulation of their radii within the range of r = 80 - 150 nm by adjusting pulse intensity. The particle generation system is compact and simple and enables operation at repetition rates exceeding 10 kHz.

An exceptional aspect of our method lies in its ability to produce pristine silicon spheres directly in a vacuum environment, otherwise unattainable in air due to rapid oxidation. Silicon, with its high infrared polarizability, tunable electrical conductivity, and low work function, holds substantial significance in levitated optomechanics, cavity cooling, and emerging quantum interference experiments. Furthermore, coupling our particle source with an infrared cavity demonstrates the temporary trapping of gold nanoparticles.

Related papers:
2013 Cavity cooling of free silicon nanoparticles in high vacuum
2014 Laser printing of silicon nanoparticles with resonant optical electric and magnetic responses

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