Surface plasmon polariton Wannier-Stark ladder

Area of Science:

• * Physics, specifically condensed matter physics and optics.
• * Nanophotonics and plasmonics.
• * Materials science involving metallic nanostructures.

Background:

• * Surface plasmon polaritons (SPPs) are electromagnetic waves confined to the interface between a metal and a dielectric.
• * Controlling SPP propagation is crucial for nanophotonic devices.
• * Periodic structures can modify SPP behavior, but complex behaviors like Stark ladders are less explored in this context.

Purpose of the Study:

• * To investigate the propagation characteristics of SPPs on a metal surface with periodically modulated groove depths.
• * To explore the emergence of analog Wannier-Stark ladder phenomena in SPP systems.
• * To analyze the frequency-dependent transmissivity and radiated power.

Main Methods:

• * Utilized the finite-difference time-domain (FDTD) method for numerical simulations.
• * Modeled SPP propagation on a planar metal surface with N rectangular grooves of uniform width but varying depths.
• * Analyzed the frequency response of transmissivity and radiated power.

Main Results:

• * Observed N equally spaced dips in the transmissivity of SPPs as a function of frequency.
• * Detected N equally spaced peaks in the power radiated into the vacuum.
• * Identified these spectral features as signatures of a surface plasmon polariton analog of a Wannier-Stark ladder.

Conclusions:

• * The periodic modulation of groove depths on a metal surface leads to quantized energy levels for SPPs, analogous to Wannier-Stark ladders in solid-state physics.
• * This phenomenon offers a new pathway for controlling and manipulating SPPs.
• * The findings have implications for the design of novel plasmonic devices and metamaterials.