The combination of modern nanofabrication techniques and advanced computational tools has opened unprecedented opportunities to mold the flow of light. In particular, discrete photonic structures can be designed such that the resulting light dynamics mimics quantum mechanical condensed matter phenomena. By mapping the time-dependent probability distribution of an electronic wave packet to the spatial light intensity distribution in the corresponding photonic structure, the quantum mechanical evolution can be visualized directly in a coherent, yet classical wave environment. On the basis of this approach, several groups have recently observed discrete diffraction, Bloch oscillations and Zener tunnelling in different dielectric structures. Here we report the experimental observation of discrete diffraction and Bloch oscillations of surface plasmon polaritons in evanescently coupled plasmonic waveguide arrays. The effective external potential is tailored by introducing an appropriate transverse index gradient during nanofabrication of the arrays. Our experimental results are in excellent agreement with numerical calculations.

Domain patterns in barium titanate (BaTiO3) were investigated by piezoresponse force microscopy (PFM) using a variable-temperature scanning force microscope. By analyzing the vertical and the lateral PFM images, the directions of polarization of the individual domains, i.e., 6 directions for the tetragonal and 12 directions for the orthorhombic phase, could be identified. The change of a domain pattern when submitting the crystal to a temperature ramp between +20° and −20° synchronized to the PFM scanning process was directly monitored. Finally, the possible conversions between specific domain orientations upon heating/cooling the crystal across the phase transition were experimentally confirmed.

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Ferroelectric domains are engineered in lithium niobate crystals by scanning strongly absorbed UV laser light across the crystal surface. Focused UV laser light can not only write, but also erase previously written domains on the non-polar faces of lithium niobate, which allows tailoring of domain patterns. Such domain pattern were generated and afterwards investigated by piezoresponse force microscopy and hydrofluoric acid etching. It was found that domains with dimensions down to 2 µm can be engineered, which was ∼30% of the focus beam diameter (7 µm) used for writing the domains. Additionally, it was found that an unique domain depth profile can be formed, which is inclined to the crystallographic axes and can be described as 'halfcrescent-shaped'.