Femtosecond imaging of spatial deformation of surface plasmon polariton wave packet during resonant interaction with nanocavity

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.

Observation of ultrabroadband striped space-time surface plasmon polaritons

“…Along the transverse direction, the fluorescence image shows a periodicity equal to a half of that of a strived ST-SPP, reflecting two antinodes incorporated in one cycle of the transverse profile. The axial beating is the result of interference between the free-space ST wave packet and the surface-bound striped ST-SPP [55,56]. These observations provide evidence for the feasibility of synthesizing arbitrary ST-SPPs that incorporate a multiplicity of spatial frequencies [50].…”

“…Typically, the out-ofplane component dominates the field intensity. The two-photon-fluorescence emission is collected with an objective lens (M Plan Apo SL20X, Mitutoyo) equipped with a band-pass filter transmitting light in the range 475 − 495 nm (Semrock, FT-02-485/20-25), followed by a CCD camera (Rolera EM-C2, QImaging) [55,56]. The intensity I(x, z) detected by the CCD camera is a time integral of the fourth power of the total electric field.…”

Observation of Ultrabroadband Striped Space-Time Surface Plasmon Polaritons

“…The axial beating is the result of interference between the free-space ST wave packet and the surface-bound striped ST-SPP. 55,56 These observations provide evidence for the feasibility of synthesizing arbitrary ST-SPPs that incorporate a multiplicity of spatial frequencies. 50 ■ THEORETICAL FORMULATION Theory of ST Wave Packets.…”

“…Along the transverse direction, the fluorescence image shows a periodicity equal to a half of that of a striped ST-SPP, reflecting two antinodes incorporated in one cycle of the transverse profile. The axial beating is the result of interference between the free-space ST wave packet and the surface-bound striped ST-SPP. , These observations provide evidence for the feasibility of synthesizing arbitrary ST-SPPs that incorporate a multiplicity of spatial frequencies …”

“…Typically, the out-of-plane component dominates the field intensity. The two-photon-fluorescence emission is collected with an objective lens (M Plan Apo SL20X, Mitutoyo) equipped with a band-pass filter transmitting light in the range 475–495 nm (Semrock, FT-02-485/20-25), followed by a CCD camera (Rolera EM-C2, QImaging). , The intensity I ( x , z ) detected by the CCD camera is a time integral of the fourth power of the total electric field.…”