H. Glaeske

Intrinsic optical bistablility of an ultrathin film consisting of oriented linear aggregates

A theoretical study of transmittivity of an ultrathin film (of thickness smaller than an optical wavelength) consisting of oriented linear aggregates is carried out. We show that within a certain domain of the incident field amplitude, optical transitions of a single disordered aggregate, the eigenstates of which are represented by the Frenkel exciton states, can be treated in the framework of a two-level approximation. This allows us to claim that an ensemble of linear aggregates is analogous to that comprised of inhomogeneously broadened two-level systems. Based on this analogy, we show that the transmittivity of the film can manifest a bistable behavior originating from the coupling of the aggregates via the emission (far-zone) field. This mechanism of bistability differs from that occurring in a single perfect aggregate. In the latter case, bistability results from the population-dependent resonance frequency shift of an individual aggregate, originating from the coupling of the molecules via the dipo...

Effect of exciton-exciton annihilation on optical bistability of a linear molecular aggregate

Abstract A theoretical study of the optical bistable response of a linear molecular aggregate modelled as a linear chain of molecules is carried out, making use of the one-molecule density matrix approach in which the intermolecular dipole-dipole interaction is included explicitly. The effect of exciton-exciton annihilation on the bistable behaviour is analyzed. One point of view seems to be that the annihilation channel of relaxation can destroy the bistability. However, we found that the bistable behaviour may be observable even when the annihilation constant greatly exceeds the intermolecular dipole-dipole interaction being responsible for the aggregate bistability.

Channels of the exciton–exciton annihilation in one-dimensional aggregates at low temperature

Abstract Exciton–exciton annihilation is implied to be in fact a unique channel of exciton degradation in linear molecular aggregates and conjugated polymers as the pump intensity rises. However, at low temperatures, excitons represent rather immobile than movable quasi-particles due to the localization effect. We analyze possible channels of exciton–exciton annihilation, which seem to be natural ones under the conditions of localization and low temperature, and calculate the corresponding rates.

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

A theoretical study of transmittivity of an ultrathin film (of thickness smaller 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 eigenstates of which are represented by Frenkel exciton states, can be treated in the frame of two- level approximation. This allows us to claim that an ensemble of linear aggregates is analogous to that comprised of inhomogeneously broadened two-level systems. Based on this analogy, we report that transmittivity of the film can manifest a bistable behavior originating from coupling of aggregates via the emission (far-zone) field. Estimates of driving parameters show that such well studied objects as J-aggregates of polymethine dyes provide a real basis to realize it.

Mirrorless optical bistability of an ultrathin glassy film built up of oriented J-aggregates: Effects of two-exciton states and exciton–exciton annihilation

We theoretically analyze the optical response of an ultrathin film with accounting for the effects of creating two exciton states as well as their annihilation in an individual aggregate. We show that these two processes do not violate mirrorless optical bistability of the film found in the framework of the ground-to-one exciton state transitions but, contrary to that, act towards improving the conditions for bistability to occur. In particular, the killing action of inhomogeneous broadening of the one-exciton absorption spectrum may be considerably reduced due to the exciton–exciton annihilation process giving hope for creating a unit for an all-optical device based on such systems.

Effect of exciton-exciton annihilation on optical bistability of one-dimensional Frenkel excitons

Abstract The effect of exciton-exciton annihilation on the bistable behaviour of one-dimensional Frenkel excitons is analysed. It is found that the bistable behaviour may be observable even when the annihilation constant greatly exceeds the intermolecular dipole dipole interaction being responsible for the excitonic bistability.

Abrupt switching and hysteresis of transmittivity of an ultrathin film consisting of J-aggregates

A theoretical study of transmittivity of an ultrathin film (of thickness smaller than an optical wavelength) comprized of linear molecular aggregates is carried out. We report on an abrupt change of transmittivity of the film at a certain magnitude of the incident field. The effect originates from the coupling of aggregates via the emitting field. Estimates of driving parameters show that such well-studied objects as J-aggregates of polymethine dyes provide a real basis to realize it.

Quantum Beats in Transient Spectroscopy of J-Aggregates

Quantum beats in transient absorption of PIC-J-aggregates, modelled by a modified 3-level-system are calculated. Experimental conditions for the possibility of their observation are investigated. The influence of the temperature dependent phase relaxation on the temporal evolution of quantum beat signals is considered.