Polarization controllable plasmonic focusing based on nanometer holes.

Two kinds of plasmonic lenses are proposed based on phase compensation. Each kind of plasmonic lens is comprised of four sets of nanohole arrays, and two sets of face-to-face nanohole arrays are planar symmetric. The adjustment of separation and the rotation angle of holes compensates, respectively, for the phase difference of the surface plasmon polaritons reaching to the focal spot. The different design principles make the proposed plasmonic lenses show the different polarization dependence focusing. Two or four foci of the first kind of plasmonic lens and two controllable foci focusing of the second kind of plasmonic lens can be utilized as optical switch and logic judgment. Theoretic analysis, numerical calculations and experiment measurement verify the focusing performance of our proposed plasmonic lenses. The focusing functionality and versatility of our proposed structures are helpful for extending the applications of plasmonic lenses in integrated optics.