Mechanisms of optical limiting in a COANP solution containing fullerenes C70: Applicability for the optoelectronics devices

2016

J. Phys.: Conf. Ser.

Abstract. The advanced investigations of π-conjugated organic molecule COANP sensitized with fullerenes have been revealed to consider this system as an affective medium for optical limiting and phase modulation. The special accent has been given to influence of the nanostructured relief at the interface on the spectral and photoconductive features. IntroductionMaterials with π-conjugated organic molecules [1][2][3][4] are ones of the perspective media used for optical modulators, in particular for optical limiter. These materials can be polarized at a distance more than molecules dimension that leads to the appearance of nonlinear properties of the medium.In our previous works [5,6] we have considered the optical limiting properties of 2-cyclooctylamino-5-nitropyridine (COANP) solution doped with fullerenes C 70 . Experiments demonstrated the limiting of the laser radiation with energy density from 0.1 J/cm 2 up to 0.6 J/cm 2 . We have obtained the maximum attenuation of the laser radiation with energy density of 0.35 J/cm 2 for the solution COANP-C 70 with fullerene content of 20 wt.%. The energy value passed through solution has been decreased up to 18 times.Reverse saturable absorption (RSA) and the complex formation process have been considered as the main mechanisms responsible for the optical limiting (OL) of COANP-C 70 system. The RSA mechanism, as the first one, is based on a difference in cross section for excited state of the fullerene molecule and unexcited ones. The cross section of singlet-triplet excited states in the fullerene is larger than the one of the unexcited molecule. The population of excitation levels increases with laser energy increase, so absorption increases as well.The complex formation process, as the second OL mechanism, is corresponded to the following reason. Intermolecular charge transfer complex with large absorption cross section can be formed in π-conjugated organic system doped with C 70 due to the large electron affinity energy of fullerene. The electron affinity of acceptor fragment NO 2 in COANP is close to 0.45 eV. This parameter for fullerene is 2.65 eV that leads fullerene attracts weakly bound electrons from COANP donor part. Moreover, the distance for the electron pathway is larger for the intermolecular charge transfer than the one for the intramoleculat transfer process. These two facts provoke the formation of the large dipole moment correlated with the increased absorption cross section under the laser irradiations. The model of the

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Section: Introductionmentioning

confidence: 99%

COANP-fullerenes system for optical modulation

2016

J. Phys.: Conf. Ser.

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Functional Smart Dispersed Liquid Crystals for Nano- and Biophotonic Applications: Nanoparticles-Assisted Optical Bioimaging

Journal of Nanomaterials

Zubtcova

et al. 2016

Functional nematic liquid crystal structures doped with nano- and bioobjects have been investigated. The self-assembling features and the photorefractive parameters of the structured liquid crystals have been comparatively studied via microscopy and laser techniques. Fullerene, quantum dots, carbon nanotubes, DNA, and erythrocytes have been considered as the effective nano- and biosensitizers of the LC mesophase. The holographic recording technique based on four-wave mixing of the laser beams has been used to investigate the laser-induced change of the refractive index in the nano- and bioobjects-doped liquid crystal cells. The special accent has been given to novel nanostructured relief with vertically aligned carbon nanotubes at the interface: solid substrate-liquid crystal mesophase. It has been shown that this nanostructured relief influences the orienting ability of the liquid crystal molecules with good advantage. As a result, it provokes the orientation of the DNA. The modified functional liquid crystal materials have been proposed as the perspective systems for both the photonics and biology as well as the medical applications.

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Study of optical limiting mechanisms for a pyridine complex sensitized by C_70 fullerene and Malachite green dye

2016

J. Opt. Technol.