Fano resonances in nanoscale structures

Nowadays nanotechnology allows to scale-down various important devices\n(sensors, chips, fibres, etc), and, thus, opens up new horizon for their\napplications. Nevertheless, the efficiency most of them is still based on the\nfundamental physical phenomena, such as resonances. Thus, the understanding of\nthe resonance phenomena will be beneficial. One of the well-known examples is\nthe resonant enhancement of the transmission known as Breit-Wigner resonances,\nwhich can be described by a Lorentzian function. But, in many physical systems\nthe scattering of waves involves propagation along different paths, and, as a\nconsequence, results in interference phenomena, where constructive interference\ncorresponds to resonant enhancement and destructive interference to resonant\nsuppression of the transmission. Recently, a variety of experimental and\ntheoretical work has revealed such patterns in different branches of physics.\nThe purpose of this Review is to demonstrate that this kind of resonant\nscattering is related to the Fano resonances, known from atomic physics. One of\nthe main features of the Fano resonances is the asymmetric profile. The\nasymmetry comes from the close coexistence of resonant transmission and\nresonant reflection. Fano successfully explained such a phenomenon in his\nseminal paper in 1961 in terms of interaction of a discrete (localized) state\nwith a continuum of propagation modes. It allows to describe both resonant\nenhancement and resonant suppression in a unified manner. All of these\nproperties can be demonstrated in the frame of a very simple model, which will\nbe used throughout the Review to show that resonant reflections observed in\ndifferent complex systems are indeed closely related to the Fano resonances.\n