Engineering the wavefront of light in random media allows the control of wave propagation in space and time by exploiting the spatial and spectral degrees of freedom introduced by multiple scattering (M. Mounaix et al, Phys. Rev. Lett. 116, 253901 (2016)). To apply this far-field control strategy and focus electromagnetic energy at the nanoscale, it is necessary to introduce scatterers that feature strongly enhanced and confined optical fields such as plasmonic nanoantennas. In particular, semi-continuous gold films close to the percolation threshold feature high local field enhancements (S. Gresillon et al, Phys. Rev. Lett. 82, 4520 (1999)) but also propagating surface plasmon waves that can be controlled using a spatial light modulator (P. Bondareff et al, ACS Photonics 2, 1658 (2015)). In this presentation, we demonstrate how controlling the phase of an incoming pulsed laser on a chosen 10 µm x 10 µm area of a random plasmonic metasurface allows us to optimize the two-photon luminescence (TPL) of gold at a given position of the sample. The optimized TPL intensities, that are associated with strong local field enhancements, are increased by a factor of 50 for semi-continuous films that are close to percolation compared to samples far from it, demonstrating that the morphology and randomness of the plasmonic film play an essential role in the control of nonlinear luminescence. Furthermore, we show that TPL intensities can be enhanced at any position of a percolated film, opening exciting perspectives for the wavefront engineering of local field enhancements in random plasmonic metasurfaces.
Gauthier Roubaud, Pierre Bondareff, Giorgio Volpe, Sébastien Bidault, Sylvain Gigan, and Samuel Gresillon, "Local optimization of nonlinear luminescence in random gold metasurfaces by far-field wavefront control (Conference Presentation)," Proc. SPIE 10541, Photonic and Phononic Properties of Engineered Nanostructures VIII, 105410D (Presented at SPIE OPTO: January 30, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2286615.5751529791001.
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