Several quantumoptical analogous in plasmonic nanostructures

There has been a long exploration on classical optical wave phenomena that are analogous to different effects that are originally found in quantum systems. Such studies have twofolded significance: 1) the quantum effects bring a lot of new concepts and proposals for building photonic systems with unprecedentedly extraordinary properties; 2) optic and photonic systems offer rather unique advantages on examining the fundamentals of the quantum mechanisms, for example, by direct mapping of the wave function evolution in both coordinate and momentum space with modern imaging and microscopy techniques. We present a short review on a variety of coherent optical interactions in plasmonic nanostructures that are akin to certain quantum physics originally discovered in condensedmatter and electronic systems. More specifically, we show that Fano resonance, electromagneticallyinduced transparency, toroidal resonance, as well as paritytime symmetry mediated nontrivial phenomena are sustainable and controllable in judiciously designed nanoantennas, waveguides, and their coupling systems, leading to interesting farfield, nearfield, and transportation properties. These quantumoptical analogies are easily understood with coherent optical mode interactions that can be well described by the coupled mode theory (CMT). Both temporal and spatial CMT results are shown and compare favorably to full wave electromagnetic calculations.