Fibred Plasmonic Nano-Tweezers – FiPlaNT

The main objective of the present project is the realisation of an original fibred, plasmonic nano-tweezers (FiPlaNT), its application to nanoparticle trapping and the optical characterisation of trapped particles. The experimental work will be accompanied by the theoretical description of the FiPlaNT set-up to support device optimisation and in-depth interpretation of the experimental results.

In its final configuration the FiPlaNT set-up will be made of two metallised fibre tips facing each other at a controlled distance in the 50 - 500 nm range. This device will combine the advantages of the fibred tweezers and the surface plasmon tweezers, i.e. high trapping forces at low light intensity enabling the trapping of particles of a genuine nano-scale, high flexibility due to in situ optimisation and control of the relative and absolute fibre positions, distribution of the light intensity directly into the trapping cavity, and freestanding cavity without any substrate. To the best of our knowledge, the FiPlaNT set-up will be the first genuin plasmonic tweezers, allowing not only nanoparticle trapping but also their manipulation at the nanoscale. This functionality, which cannot be realized with substrate based plasmon traps is however of paramount interest to the nanoscience community.

Single and multiple nanoparticle trapping will be demonstrated using different types of nanoparticles, among which nanodiamonds and rare earth-doped nanocrystals or nanoneedles. These particles will be elaborated and optimized in the framework of the project. Each of these systems differs from its dielectric and spectroscopic properties : index of refraction, number of emission centres per particle, absorption and emission wavelength, and emission lifetime.
An important part of the FiPlaNT project is also the development of theoretical tools to describe the complex electromagnetic field distribution inside the trapping cavity and the resulting optical forces. The theoretical considerations include the influence of the trapping cavity on the emission and absorption properties of fluorescent particles.

The ultimate challenge of the FiPlaNT project is to demonstrate that our nano-optical tweezers represents a new tool for the investigation of physical properties of nanoparticles, especially concerning their interactions with their environment. These concern dielectric and plasmonic effects, but also energy transfer processes towards other systems in the surrounding of the particles.