The optical limiting efficiency and the possibility of extending the spectral and time ranges of optical limiters based on fullerene-containing media are studied. The optical limiting of pulses of different durations in solutions of C 60 and higher fullerenes, the triplet—triplet transfer in multicomponent fullerene-containing solutions, and the electron transfer in the C 60 -tetramethylbenzidine-perylene system are investigated.

A simple equation describing the optimum relation of the parameters of doped nematochiral cells for use in real systems of switching and limiting of laser radiation is obtained based on analytical estimates. The adequacy and feasibility of the derived relation is confirmed experimentally.

A phenomenological study of a specific radical ion mechanism of formation of metastable products is presented. Energy level diagrams of fullerene C(60), tetramethylbenzidine, perylene, and radical ion pairs in toluene and benzonitrile are constructed. The possibility for obtaining fast optical switching and limiting in solutions of C(60) fullerene, tetramethylbenzidine, and perylene in toluene is analyzed.

Spectral and some nonlinear optical properties of multicomponent solutions, which contain fullerene C-60, perylene, and tetramethylbenzidine, are investigated. In such systems, enhanced optical limiting and all-optical switching are due to a formation of radical ions by a photoinduced electron transfer. A diagram of electronic states is thermodynamically calculated and prove for efficiency of the photoinduced electron transfer via the excited singlet state of C-60 is shown.

This paper presents experimental results and a theoretical analysis of the features of the absorption-emission kinetics in optically dense media accompanying Stokes and anti-Stokes excitation by picosecond laser pulses. The studies were carried out with a solution of rhodamine 101. It is shown that the observed features of the photodynamics of the solutions are associated with manifestations of collective photoinduced luminescence, light quenching, and two-photon absorption. (c) 2006 Optical Society of America.

The conditions of occurrence of collective photoinduced luminescence in model solutions are determined. The transmittance and luminescence of concentrated solutions of rhodamine 101 under excitation by laser pulses in the Stokes and anti-Stokes spectral ranges are studied. It is shown that, at high pump energies, collective photoinduced luminescence, which competes with induced radiation, plays a significant role in luminescence generation. Temperatures of heating and cooling of solutions are estimated. The photodynamics of cooling of solutions of complex molecules under their pulsed (Stokes and anti-Stokes) excitation is analyzed.

Original compositions in the form of suspensions of astralenes with luminescing solubilizers in various solvents, including liquid crystals (LCs), are developed. Using an LC composition as an example, the possibility of extending the dynamic range of optical limiting due to the joint action of two-photon absorption in the LC matrix and stimulated scattering by carbon nanoparticles is demonstrated. The spectral and luminescent characteristics of such suspensions are determined. The role played by the photochemical factor in the photodynamics of optical limiting in carbon heteronanostructures is discussed.

Original composites consisting of suspensions of astralenes With luminescent solubilizers in various solvents have been synthesized for the first time by the method of noncovalent solubilization. The spectroluminescence characteristics of such composites have been measured. A hand corresponding to the S-11 transition between van Hove singularities has been detected in the 1800-nm region in the absorption Spectrum of a Suspension of astralenes in a liquid crystal. The effect of optical limitation of laser radiation has been investigated in certain composites. A discussion is given of the role of noncovalent solubilization and of the formation of an ion-radical pair in the photodynamics of optical limitation in carbon nanoheterosystems. (c) 2005 Optical Society of America.

The transmittance and luminescence of concentrated Solutions of rhodamine 101 excited by laser Pulses in the Stokes and anti-Stoke regions of the spectrum have been experimentally investigated. It is shown that a substantial role in forming the luminescence is played at large pump energies by collective photoinduced luminescence, which competes with induced emission. Estimates are inade of the heating and cooling of Solutions. (c) 2005 Optical Society of America.

Optical limitin:g was experimentally studied in C-60 fullerene-based multicomponent solutions that are characterized by photoinduced electron-transfer processes with the formation of ion-radical pairs. The limitation efficiency in these solutions increased as a result of enhancement of absorption in the molecular system in an excited state. It was found that the spectral and time capabilities of limiters based on fullerene-containing media can be extended with the use of radical ions.

A non-covalent solubilization technique allowed us to synthesize original compositions such as suspensions of astralenes in nematic liquid crystal (LC). Study of their spectral luminescent parameters in a planar oriented cell led to discovery of bands in the absorption spectra at 1300 and 1700 nm. In our assumption, they correspond to transitions between van Hove singularities (VHS) in electronic state densities. It gave us the opportunity to pioneer measurement of absorption dichroism in the suspensions of carbon nanoparticles and found existence of different polarizations at transitions, responsible for background absorption and absorption in the van Hove bands. The role of the photochemical factor in photodynamics of optical limiting on carbon nanoheterostructures is discussed.

The effect of photoinduced electron transfer with formation of a radical-ion pair on the characteristics of optical limiting of laser radiation in specially prepared multi-component fullerene solutions is studied. The limitation efficiency in such solutions increases due to absorption of laser radiation by molecules in a metastable state. The experimental results show that the spectral and time optical limiting ranges can be expanded due to formation of radical ions.

We have experimentally studied optical limiting in multi-component solutions containing polycyclic compounds (perylene and fullerenes) for which typical processe is photoinduced electron transfer with formation of ion pairs. Founded significant rise of limiting efficiency in such molecular systems is due to increase of absorption in the excited state. Formation of radical ions can be used for widening of spectral range of operating medium limiting.

The kinetics of optical limitation of the intensity of nanosecond laser radiation have been studied in solutions that photogenerate C-60(.-) anion radicals formed by the action of laser radiation on specially chosen multicomponent solutions. It has been demonstrated that simultaneous limitation of subnanosecond radiation of the first and second harmonics of a YAG:Nd3+ laser is possible, and it is shown to be promising to use molecular ion-radicals to improve the spectral and dynamic characteristics of fullerene-containing media. (C) 2003 Optical Society of America.

Influence of electron excitation energy transfer and secondary effects, occurred under action of laser radiation, on dynamics and efficiency of optical limiting is discussed. Two different systems, operating on effects of two-photon absorption and reverse saturable absorption, are considered as an example.

The possibility of using liquid-crystal microlenses for solving the problems of optical limiting is demonstrated. A compact optical system based on these microlenses is suggested and studied; in this system, two-photon absorption in extrinsic nematic liquid crystals is used as a limiting mechanism.

Model arrays of nonsymmetric microlenses based on a nematic liquid crystal composition with Δε=10 were manufactured and their optical characteristics were studied. The efficacy of using these devices in the optical limitation systems is demonstrated for a C 70 fullerene solution in toluene.

The features of low-threshold limitation are observed. It is shown, that one of solutions of this task is usage of effect of two-photon absorption in an impurity liquid crystal. It is stipulated by large cross-section of two-photon absorption in cyanobiphenyls. The strategy of usage of mesomorphic microlenses as structural elements of optical limiters is discussed. The experiments on optical limitation in constructions using mesomorphic microlenses are realized.

The formation of complexes in the fullerene C 70 -toluene-liquid crystal system is investigated. The precision study of spectral manifestations of the intermolecular interaction in this system is performed for two low-frequency absorption bands of C 70 . These manifestations are found to be specific for each of the bands analyzed.