Surface plasmon Fourier optics

Abstract

Surface plasmons are usually described as surface waves with either a complex wavevector or a complex frequency. When discussing their merits in terms of field confinment or enhancement of the local density of states, controversies regularly arise as the results depend on the choice of a complex wavevector or a complex frequency. In particular, the shape of the dispersion curves depends on this choice. When discussing diffraction of surface plasmon a scalar approximation is often used. In this work, we derive two equivalent vectorial representations of a surface plasmon field using an expansion over surface waves with either a complex wavevector or a complex frequency. These representations can be used to account for propagation and diffraction of surface waves. They can also be used to discuss the issue of field confinment and local density of states as they have a non-ambiguous relation with the two dispersion relations.

Enhanced Optical Chirality through Locally Excited Surface Plasmon Polaritons

“…As long as the mean free path of electrons is much shorter than the wavelength of the plasmon, macroscopic electrodynamics can be utilized to describe the optically excited surface plasmons 1 . The interactions between near-field dipole sources and surface plasmons have been investigated in detail [17][18][19][20][21][22][23][24][25][26] . Here we will look into the chiral behavior of SPPs excited by differently polarized near-field sources in vicinity of a semi-infinite metal surface, See Figure 1a for instance.…”

Polariton excitation in epsilon-near-zero slabs: Transient trapping of slow light

“…In order to rigorously prove this statement and gain deeper understanding of the underpinning physical mechanisms that support the time-domain ENZ regime, in this section we analyze the exact quasi-steady modes (virtual modes) of the slab. In our analysis we fully take into account damping processes, which include medium absorbtion and radiation leakage in vacuum, adopting the complex frequency approach [25]. We start our analysis from the curl Maxwell equations for TM fields…”

“…In our analytical calculations, we will use a similar approach to study the behavior of an electromagnetic pulse that scatters from a slab having a Lorentz dielectric response. Indeed, by considering non-monochromatic virtual modes with complex frequency [25], it is possible to drop off the effect of loss on the temporal dependence of the "mode" itself. In this complex frequency approach, it is possible to achieve the condition where the dielectric susceptibility exactly vanishes.…”

Basis for paraxial surface-plasmon-polariton packets

“…Even if this level of description may be sufficient in many situations, it ignores any possible transversal structure, thus missing, for instance, interesting cases such as nondiffractive solutions [17][18][19][20]. Therefore, a complete characterization of the evolution and the confinement properties of SPPs requires a description beyond the single plane-wave approximation [21][22][23][24] and a careful analysis of any simplification of the physical model since these can lead to incorrect outcomes [25][26][27][28].…”

“…In order to do so, we employ a rigorous formulation based on the so-called plane-wave spectrum formalism [21,22,29,30], which takes into account explicitly the losses of the metal. By exploiting the analogy with the paraxial propagation of optical beams, we introduce a set of modes that constitutes a complete basis for the solutions of Maxwell's equations for a metal-dielectric interface in the paraxial approximation.…”