Transmission switching and hysteresis in an ultrathin film of organic molecular aggregates

Summary form only given. We provide a theoretical study of transmittivity of an ultrathin layer (of thickness smaller than an optical wavelength) consisting of oriented organic molecular aggregates (J-aggregates). In spite of the fact that those are complicated systems the excited states of which have the character of Frenkel excitons, an analysis of spectroscopic data of J-aggregates shows, that in a definite area of intensity of the incoming field such films can be modeled as an ensemble of inhomogeneously broadened two-level-systems. An appropriate renormalization of the spontaneous emission rate ensures, that mainly the fewest excitonic state couples to the radiation field. Because of a quite high concentration necessary for the aggregation process itself, in such systems a mechanism of optical bistability, that is due to coupling of the single aggregates via the far-zone field is shown to be possible.