M. V. Gryaznova

New nanoheterostructures based on astralenes: Spectral characteristics and some application aspects

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.

Formation of radical ions and peculiarities of optical limiting in solution containing C60, perlyne, and tetramethylbenzidine

Spectral and some nonlinear optical properties of multicomponent solutions, which contain fullerene C60, 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 C60 is shown.

Nonlinear luminescence of high-concentration rhodamine solutions: On the problem of pulsed laser cooling

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.

Collective processes in the luminescence that accompanies picosecond excitation

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.

On the question of pulsed laser cooling. Collective luminescence and light quenching in high-concentration solutions of rhodamine 101

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 made of the heating and cooling of solutions.

Noncovalent solubilization of nanoheterogeneous astralene-based structures. The photochemical factor in optical limitation on carbon suspensions

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 band corresponding to the S11 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.

Influence of radical ions on optical limiting effect in solutions of polycyclic compounds

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.

Transfer of electronic excitation energy and secondary processes in the media used for optical limiting

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.

Features of the kinetics of optical limitation in fullerene-containing solutions during electron phototransport

The kinetics of optical limitation of the intensity of nanosecond laser radiation have been studied in solutions that photogenerate C60 -2 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:Nd31 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.