Surface Plasmon-Mediated Nanoscale Localization of Laser-Driven sub-Terahertz Spin Dynamics in Magnetic Dielectrics

Abstract

We report spatial localization of the effective magnetic field generated via the inverse Faraday effect employing surface plasmon polaritons (SPPs) at Au/garnet interface. Analyzing both numerically and analytically the electric field of the SPPs at this interface, we corroborate our study with a proof-of-concept experiment showing efficient SPP-driven excitation of coherent spin precession with 0.41 THz frequency. We argue that the subdiffractional confinement of the SPP electric field enables strong spatial localization of the SPP-mediated excitation of spin dynamics. We demonstrate two orders of magnitude enhancement of the excitation efficiency at the surface plasmon resonance within a 100 nm layer of a dielectric garnet. Our findings broaden the horizons of ultrafast spin-plasmonics and open pathways toward nonthermal opto-magnetic recording on the nanoscale.

Unidirectional and diffractionless surface plasmon polaritons on three-dimensional nonreciprocal plasmonic platforms

“…1(e)-(f), based on a naturally-available material platform, without the need to engineer complex photonic crystals or metamaterials. We note that an example of asymmetric nonreciprocal light emission under a magnetic bias has been recently demonstrated experimentally in [18], in which plasmonic effects were also used to enhance the emission directionality (see [19,20] for an overview of different magneto-plasmonic devices).…”

Helicity‐Preserving Metasurfaces for Magneto‐Optical Enhancement in Ferromagnetic [Pt/Co]N Films

“…[ 33 ] More recently, plasmon‐mediated enhancement of the IFE by two orders of magnitude was shown to realize sub‐THz spin precession confined within 100 nm thick regions of GdYbBIG. [ 34 ] However, plasmonic metals suffer from high intrinsic losses, and excessive heating could limit their performance near optical frequencies. Alternatively, greater efficiency could be realized with low‐loss dielectric nanostructures fabricated from high‐index materials that offer additional control over phase and polarization of light by virtue of their electric and magnetic Mie modes.…”

Ultrafast transport and relaxation of hot plasmonic electrons in metal-dielectric heterostructures

“…Here k SP is the SP wavevector, k in = k 0 sin θ is the in-plane component of the free-space photon momentum, k G = 2π/b is the quasiwavevector of a grating of period b, and m is an integer. Experimentally, we studied a magneto-plasmonic Au-YIG:Co crystal with b = 800 nm, gap width 100 nm, and Au thickness d = 50 nm [2]. Transmittance angular spectra taken at a series of fundamental wavelengths in Figure 2,a illustrate the SP dispersion in the near-IR range.…”