Metafocusing by a Metaspiral Plasmonic Lens

Area of Science:

• * Plasmonics and Nanophotonics
• * Metasurface Optics
• * Surface Plasmon Polaritons (SPPs)

Background:

• * Conventional in-plane plasmonic lenses face challenges in efficiency and functionality.
• * Metasurfaces offer local control, while spirality provides global control over light manipulation.
• * Existing lenses struggle with uniform focusing and polarization independence.

Purpose of the Study:

• * To design and realize a metasurface spiral plasmonic lens overcoming limitations of conventional designs.
• * To achieve highly efficient and uniform linear-polarization-independent plasmonic focusing.
• * To demonstrate advanced functionality for selective SPP manipulation and high-contrast focusing.

Main Methods:

• * Design and fabrication of a metasurface with spiral geometry.
• * Characterization using near-field optical microscopy.
• * Theoretical interpretation and numerical simulations of SPP behavior and focusing.

Main Results:

• * Achieved significantly more efficient and uniform plasmonic focusing compared to conventional lenses.
• * Demonstrated polarization-independent focusing by combining metasurface and spiral designs.
• * Showcased functional focusing with 2 orders of magnitude intensity contrast for matched circularly polarized illumination, directing all SPP power to the focal spot.

Conclusions:

• * The metasurface spiral plasmonic lens fundamentally overcomes efficiency and functionality challenges.
• * This technology enables optimal functional focusing and advanced SPP manipulation.
• * Results pave the way for applications in smart pixels, near-field microscopy, lithography, and particle manipulation.