Principal investigator : Sophie Brasselet
Metal nanostructures are interesting emitters for second harmonic generation (SHG) radiation, which occurs essentially from the non-centrosymmetry breaking at the metal-medium interface for objects of the order of 50nm-100nm size.
At MOSAIC we have developed a SHG microscope imaging technique combined with polarization resolution, in order to be able to retrieve directly structural information on such objects even if they are of sub-diffraction size. The data can be compared with a model of SHG radiation propagation through the microscope and therefore provide a valuable characterization tool. This field permits to investigate the way to optimize the nonlinear response of metal nanoparticles that can eventually be used as new types of nanosources of light, with the properties of being wavelength-tuneable and non-photobleaching.
This research is performed in collaboration with research teams in France for both fabrication and modelling issues.
Enhanced SHG on single gold nanoapertures
We demonstrate the ability of single-subwavelength-size nanoapertures fabricated in a gold metal thin film to enhance second-harmonic generation (SHG) as compared to a bare metal film. Nonlinear microscopy imaging withpolarization resolution is used to quantify the SHG enhancement in circular and triangular nanoaperture shapes.
This study has two main results :
- The SHG enhancement on circular nanoapertures is demonstrated to originate from both phase retardation effects and field enhancements at the aperture edge.
- Triangular nanoapertures exhibit superior SHG enhancement compared with circular ones, as expected from their noncentrosymmetric shape.
- Sophie Brasselet
- Vincent Maillard
- Jerome Wenger
- David Gachet (now assistant professor at Aix Marseille university)
- Peter Schoen (now research engineer at Carl Zeiss MicroImaging, Gottingen)
- Schoen P., Bonod N., Devaux E., Wenger J., Rigneault H., Ebbesen T.W., Brasselet S., Enhanced Second Harmonic Generation from individual metallic nano-apertures, Opt Lett 35, 4063-4065 (2010) - PDF