Abstract
Abstract The spatiotemporal dynamics of a surface plasmon polariton (SPP) wave packet (WP) that interacts with a plasmonic nanocavity on a metal surface are investigated via femtosecond time-resolved two-photon fluorescence microscopy and numerical calculations. The nanocavity, which consists of a metal–insulator–metal (MIM) laminar structure (longitudinal length: ∼100 nm), behaves as a subwavelength meta-atom possessing discretized eigenenergies. When a chirp-induced femto-second SPP WP is incident on the nanocavity, only the spectral component matching a particular eigenenergy is transmitted to continue propagation on the metal surface. This spectral clipping induces a spatial peak shift in the WP. The shift can be controlled by tuning the eigenenergy or chirp.
Highlights
In optical physics, the control of the spatiotemporal dynamics of light pulses has been a fascinating topic of study
We recently reported a finite-difference time-domain (FDTD) simulation study of the deformation of the temporal waveform of a surface plasmon polariton (SPP) wave packet (WP) with a femtosecond time duration and a wide spectral width transmitted through a metal–insulator–metal nanocavity (MIM-NC) [36]
For detail examination of the SPP WP, the oscillatory waveform constructed by the pump–probe interference was extracted by the following method: The constant phase of the pump-probe interference beat moves by λbeat while τd increases by 2π rad (2.7 fs), which corresponds to a cycle of the carrier wave of the laser
Summary
The control of the spatiotemporal dynamics of light pulses has been a fascinating topic of study. The tunability of material dispersion and/or optical resonance has facilitated control over group velocities of light in a variety of natural materials and artificial nanostructures, including gaseous atoms [1, 2], ultracold atoms [3], optical fibers [4], ring resonators [5, 6], photonic crystals [7, 8], plasmonic Bragg gratings [9], and metamaterials [10,11,12,13]. Negative phase and group velocities in metamaterials have been realized by using regions with negative values of both permittivity and permeability near the electric and magnetic resonance frequencies of the artificial resonator structure [10]. Spectral widths of light pulses should be narrow enough to fit within the limited frequency range. The envelope shape of the pulse remains similar before and after transmission through the natural materials or the artificial structures, the amplitude would be attenuated because of the absorption by materials
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