Go beyond the limitations for plasmonic optical trapping

Quanbo JIANG^1*, Benoit Rogez², Jean-Benoit Claude², Guillaume Baffou², Jerome Wenger²

¹Laboratoire Lumière, nanomatériaux et nanotechnologies, Université de Technologie de Troyes, Troyes, France
²Institut Fresnel, Aix Marseille University, CNRS, Marseille, France

* Presenter:Quanbo JIANG, email:quanbo.jiang@utt.fr

Immobilizing and manipulating small objects in the solution from the micron size to the nanoscale is always of interest for biologists, chemists as well as physicists. To realize it, plasmonic nanostructures have been introduced into the commercial optical tweezer module named plasmonic nano-optical tweezers (PNTs). PNTs as an upgraded version of conventional optical tweezers (Nobel Prize of 2018) go beyond the diffraction limitation to directly trap the nanosized objects under the high local intensity enhancement close to the nanostructures.

Since many factors influence this precise nano-manipulation, a very stable trapping system including an infrared trapping laser, a plasmonic nanoaperture and a fluorescence detection module is highly demanded. It allows to quantify various parameters such as trap stiffness, local temperature while trapping nano-objects. First, we introduce a method to measure the local temperature increase in the trap due to the trapping laser. Second, we manage to take advantage of this plasmonic thermal effect to generate a large-scale thermophoretic force to assist the optical gradient force. At the end, a method based on the correlation of fluorescence fluctuation of a trapped object has been developed for the trap stiffness quantification.

Keywords: Plasmonics, Optical tweezers, Nanophotonics, Thermoplasmonics