α spiral nanoslit and the higher order plasmonic vortex generation.

In view of the conciseness of a spiral nanoslit and the limited order of the generated vortex, a kind of nanometer spiral, named α spirals, is proposed to generate a higher order plasmonic vortex. Theoretical analysis provides the basis for the advancement of an α spiral. The proposed spiral can generate the plasmonic vortex and the extreme order of the generated vortex depends on parameter α.

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.

Multifocal metalens with a controllable intensity ratio.

A multifocal metalens is proposed based on the optical metasurface consisting of subwavelength gratings etched on silver film. The larger transmission of grating makes the proposed metalens have high focusing efficiency, and the exquisite design of the metasurface enables the metalens to focus the light at multiple spots with the controllable intensity ratio. The intensity ratio of focal spots is controlled by adjusting grating structures.

Metalens based on constructive interference.

A metalens consisting of nanometer rectangular holes etched on silver film is proposed, and the focusing effect is actualized in the visible region. The rectangular holes are arranged on concentric circles, and the fields excited by these holes constructively interfere due to having the same propagation phase. The propagation phase is obtained by optimizing the sizes of the rectangular holes and the radii of the circles.