Observation of plasmonic breathers propagation in a two-level system

Two-level coupled systems are commonly used to describe the dynamics of a variety of physical phenomena in coupled systems, such as spin ½ systems, electron population of atomic levels, coupled waveguides and more [1]. The system is usually described by two eigenmodes - symmetric and anti-symmetric, which when excited will propagate through the system unchanged. Such two-mode dynamics was also shown in plasmonic system, where plasmonic eigenmodes, known as long- and short-range surface plasmons, has been observed on Insulator-Metal-Insulator (IMI) and Metal-Insulator-Metal (MIM) waveguides [2]. However, when the system is excited with a superposition of the eigenmodes, it exhibits a more interesting and dynamical behavior, where the modes can exchange energy and change spatially with propagation [3]. Yet, such excitation, which requires the symmetry of excitation to be broken, is challenging and as far as we know has not been explored nor observed.