Algebra of optical dislocations with plasmonic nanostructures.

Plasmonic structures with physical and Berry-type dislocations are shown to produce vortices with phase singularity according to the system and illumination parameters. We demonstrate that, by combining the two types of dislocations in one structure, the manipulation with the topological charge of the emerging vortex beams can be controlled in an intriguing way. As a result, the plasmonic field distribution can be conveniently modified and selectively excited.

Spin-locking metasurface for surface plasmon routing.

Nanophotonic circuitry requires an ability to externally control and analyze optical signals tightly confined in subwavelength volumes. Various schemes of surface plasmon (SP) routing have been presented using active and passive metasurfaces. One of the most appealing approaches is the use of plasmonic spin-orbit interaction where the incident light spin state is efficiently coupled to an orbital degree of freedom of the surface wave. Recently, a major attention has been drawn to an additional plasmonic degree of freedom - the transverse spin and some application for near-field plasmonic manipulations have been presented. Here we propose a spin-locking metasurface incorporating a transverse spin of the SP wave to selectively route the near-field beams. Owing to the combination of the oblique incidence of circularly polarized light with the accurately designed momentum matching of the grating we achieve a precise directional control over the plasmonic distributions. The experimental verification of the directional launching is performed by a time-resolved leakage radiation measurements allowing one to visualize the shape and the dynamics of the excited beam.

Effect of measurement on the ballistic-diffusive transition in turbid media.

The dependence of the transition between the ballistic and the diffusive regimes of turbid media on the experimental solid angle of the detection system is analyzed theoretically and experimentally. A simple model is developed which shows the significance of experimental conditions on the location of the ballistic-diffusive transition. It is demonstrated that decreasing the solid angle expands the ballistic regime; however, this benefit is bounded by the initial Gaussian beam diffraction. In addition, choosing the appropriate wavelength according to the model's principles provides another means of expanding the ballistic regime. Consequently, by optimizing the experimental conditions, it should be possible to extract the ballistic image of a tissue with a thickness of 1 cm.

Transition from the ballistic to the diffusive regime in a turbid medium.

By varying the absorption coefficient and width of an intralipid-India ink solution in a quasi-one-dimensional experiment, we investigate the transition between the ballistic and the diffusive regimes. The medium's attenuation coefficient changes abruptly between two different values within a single mean free path. This problem is analyzed both experimentally and theoretically, and it is demonstrated that the transition location depends on the scattering coefficient as well as on the measuring solid angle.