Bistable behavior of transmittivity of an ultrathin film comprised of linear molecular aggregates

A theoretical study of transmittivity of an ultrathin film (of thickness sm aller than an optical wavelength) consisting of linear molecular aggregates is carried out. We show that within a certain domain of the incident field amplitude, optical transitions of a single disordered aggregate, the eigen states of which are represented by Frenkel exciton states, can be treated i n the frame of two- level approximation. This allows us to claim that an en semble of linear aggregates is analogous to that comprised of inhomogeneous ly broadened two-level systems. Based on this analogy, we report that trans mittivity of the film can manifest a bistable behavior originating from cou pling of aggregates via the emission (far-zone) field. Estimates of driving parameters show that such well studied objects as J-aggregates of polymeth ine dyes provide a real basis to realize it. (C) 1999 Published by Elsevier Science B.V. All rights reserved.