Planar Plasmonic Devices for Controlling Polarization of Light

Sammanfattning: Planar nanostructures made of noble metal can efficiently control transmission of light, thanks to surface plasmon polaritons (SPPs) mediated through interaction between such a structure and incoming light. In this thesis, we numerically characterize, with a 3D finiteelement method, three types of plasmonic devices: plasmonic radial/azimuthal filter, plasmonic quarter-wave plate made of a periodic array of round holes in a thin metallic film, and a plasmonic quarter-wave plate with a periodic array of cross-shaped apertures. The plasmonic polarization filter is formed by a series of concentric equidistant gold rings, and it can transmit the radially polarized light and block the azimuthally polarized light. The quarter-wave plate with round holes has a different lattice constant along two Cartesiancoordinate directions that enable different phase retardations for two orthogonally polarized incident waves; hence, it can convert a linearly polarized light to a circularly polarized light. For the quarter-wave plate with an array of cross-shaped apertures, it utilizes the different lengths of horizontal/vertical arms to manipulate the phase retardations. All of these devices have sub-micron thicknesses, unlike their traditional counterparts that are bulky and inconvenient for integration purposes. Fabrication of the wave plate with cross-shaped apertures was attempted in collaboration with members in the Optics and Photonics unit at KTH.