Sujet de stage / Master 2 Internship

The aim of the internship will be to analyse the optical properties (fluorescence and frequency conversion, in particular 2nd harmonic generation - SHG) of nanometric dielectric particles in view of their future implementation for labelling and imaging in biology. The internship will include two parts: (1) the study of the SHG signal enhancement of these particles following their coupling to a plasmonic nano-antenna. (2) the possibility of controlling the emission properties of these particles by piezoelectric effect.

Following initial work carried out in the framework of a collaboration between our laboratory and two other laboratories on the Saclay plateau (ENS Paris-Saclay/ LUMIN and CentraleSupelec/ SPMS), we have been able to demonstrate the interest of (possibly doped) BaTiO3 dielectric nanoparticles for optical imaging in biological environments. More particularly, the luminescence and frequency conversion properties (second harmonic generation - SHG) of these particles make them promising markers for long term applications in the monitoring of intracellular transport in neural networks, or the measurement of extracellular transient electric potential in neurons.

The objective of the internship will be to analyse the optical properties of small BaTiO3 particles (< 100 nm) using a characterisation bench coupling an atomic force microscope (AFM) to an optical microscope associated with various laser excitations. The internship will consist of two parts:

In a first part, we will demonstrate the possibility of enhancing the SHG signal of these particles following their coupling to plasmonic nanoantennas. In particular, we have at our disposal nanoparticles covered with gold, for which first simulations suggest interesting enhancement effects.
The second part of the internship will consist in studying the possibility of modulating the particle response (frequency conversion or luminescence in the case of rare-earth doped particles) following a deformation of the crystal obtained by inverse piezoelectric effect.

The host team is the Nanophotonics group of SPEC/LEPO. For the needs of its research, the group has developed an important know-how in the coupling of optical measurements with local probe microscopies. The team has several experimental benches of this type, operating in air or under ultra-high vacuum: optics and nonlinear optics of nano-objects, new methods of optical microscopy with active probe ...

The role of the student will range from sample preparation, to the characterization of their frequency conversion properties (spectral and polarization-resolved analyses). He will also participate in the interpretation of the results that will be obtained.