“Dark” States As a Particular Case of the Emission Spectrum of an Exceptional Surface Wave

Under conditions of total internal reflection (TIR) of a plane bulk electromagnetic wave incident from outside on the surface of an optically transparent layered structure, the case where the numerator and denominator of the input surface wave impedance turn simultaneously to zero may correspond to the formation of a “dark” state. This is related to the occurrence of a point of degeneracy of the spectra of leaking exceptional surface waves (ESWs) of the first and second kind against the background of the continuous spectrum of radiative modes. For these waves, the instantaneous energy flux through the interface with a semibounded optical denser medium in an open radiative channel is zero at any instant. When approaching the point of dark state occurrence, the local maxima of the effects of first-order nonspecular reflection, accompanying resonant excitation of leaky ESWs, unlimitedly increase.