By controling the 2D growth of Au colloids and by studying teir non-linear optical properties, E. Dujardin, A. Arbouet, C. Girard et al. Demonstrate that plasmonic modes can be directly probed by optical microscopy. These results, published in Nature Materials, open the way to a new optical information paradigm based on the engineering of plasmonic modes. DOI : 10.1038/NMAT3581
Des états plasmoniques 2D codent l’information
Nature Materials (2013) DOI 10.1038/NMAT3581
Metallic nanoprisms have been synthesized by a colloidal chemistry approach enabling the selected growth of well-defined facets. Their prismatic shape in equilateral triangles with various degrees of apex truncation and their lateral size in the micrometer range for a mere 20 nm in thickness turn these particles into resonators in which the collective oscillations of free electrons, named surface plasmons, can be optically excited. Thanks to the high crystalline quality of the nanoprisms, these plasmons undergo very limited dissipation and damping and so are reflected numerous times off the edges of the crystal. The CEMES team has successfully imaged the spatial distribution of the electric field associated with these optical resonances by non-linear optical microscopy. Using a femtosecond laser, they have induced a two-photon luminescence, which they theoretically demonstrate to be revealing not only the local electric field but also the plasmonic modes of the optically excited electrons. These modes are extremely sensitive to the exact prism shape. The excellent match between their new theoretical model and the experimental optical data has enabled the exploration of more complex structures such as coupled prism pairs. They thus demonstrate that the plasmonic states in interacting prisms are markedly different from those borne by the individual partners. The authors propose to exploit such a golden tiling with couple prisms to implement a new optical processing paradigm. The operating principle of a double modal logic gate is exposed as the next experimental challenge.