Abstract
We report that the effect of an external magnetic field on the propagation of surface plasmons can be effectively modified through the coupling between localized (LSP) and propagating (SPP) surface plasmons. When these plasmon modes do not interact, the main effect of the magnetic field is a modification of the wavevector of the SPP mode, leaving the LSP virtually unaffected. Once both modes start to interact, there is a strong variation of the magnetic field induced modification of the SPP dispersion curve and, simultaneously, the LSP mode becomes sensitive to the magnetic field.
Highlights
Optical systems providing asymmetric propagation between the backward and forward directions are interesting both from the fundamental and the applied point of view [1]
This reinforces our previous statement, allowing us to associate the structure L with the LSP of gold disks and P1 with a surface plasmon polaritons (SPP) of the trilayer. Since it is the periodic disks array which enables the coupling of light with the propagating surface plasmon modes of the trilayer, the energy at which the in-plane wavevector of the incident light matches the SPP wavevector will depend on both the incident angle and the array period [18,19,20]
It is worth noticing that we have hints in the transverse Magneto-Optical Kerr Effect (TMOKE) spectra of a second S-like structure at lower frequencies corresponding to this lower SPP mode, but it is too weak to unambiguously discern it within the noise level
Summary
Optical systems providing asymmetric propagation between the backward and forward directions are interesting both from the fundamental and the applied point of view [1]. The structuration of the magneto-optical dielectrics in what are called magnetic photonic crystals allows a further control of the effect of the magnetic field on the propagation of light, and with an appropriate design the magnetic field induced modification of the photonic band structure could be as important as to allow the appearance of unidirectional propagating modes [3,4,5,6,7,8]. These works have opened the door to a new range of magneto-photonic devices immune to back-scattering losses. This result points out the feasibility of designing more complex magnetoplasmonic structures with tailored asymmetric propagation
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