Localization of plasmon modes in a 2D photonic nanostructure with a controlled disorder.

In this paper, we focus on the optical properties of disordered hole arrays etched in a gold thin film. The disorder is induced and controlled using hole displacements following a Gaussian distribution and starting from a periodic array. The nanostructures present a transition from ordered arrays to short-range ordered arrays and random arrays by increasing the disorder amount. The associated optical properties are characterized in far and near fields by complementary approaches (absorption spectroscopy, classical scanning near field optical microscopy (SNOM) and Finite Difference Time Domain (FDTD) simulations). By increasing the disorder, a broadened absorption up to 30% in the far-field is achieved. Experiments in agreement with FDTD simulations point out the energy localization induced by the disorder and the dependence on the amount of disorder and on the excitation wavelength. By using a controlled disorder, we also show that the effect of these two parameters is also closely linked.