This study is conducted in collaboration with Antoine Moreau, Department of Electromagnetism and Nanophotonics, Blaise Pascal Institute, France.
The propagation of light in a slit between metals is known to give rise to guided modes. When the slit is of nanometric size, plasmonic effects must be taken into account, since most of the mode propagates inside the metal. Indeed, light experiences an important slowing-down in the slit, the resulting mode being called gap-plasmon. Hence, a metallic structure presenting a nanometric slit can act as a light trap, i.e. light will accumulate in a reduced space and lead to very intense, localized fields. Recently, the chemical production of random arrangements of nanocubes on gold films at low cost was proved possible by Moreau et al. Through numerical experiments, it was determined that the natural curvature of the cube edges obtained by the production process has a major impact on the characteristics of the device, since it shortens the cavity holding the gap plasmon.
Here, we show the repartition of the norm of the H field Fourier transform at resonance for a 70nm-side gold nanocube described by a generalized dispersive model. The cube is put on a thick gold slab covered by a dielectric spacer. Its edges are rounded with a 3nm radius.
Simulation of electromagnetic waves propagation in nano-optics with a high-order discontinuous Galerkin time-domain method