Photo-physical processes in systems containing SWCNT -based hybrids with regard to optical power

limiting

Andrey Yu. Vlasov', Inna M. Belousova2, Ivan M. Kislyakov3

, Department of Chemistry, st. Petersburg State University, St. Petersburg, Russia 2 Department of Nanophotonics, Vavilov State Optical Institute, St. Petersburg, Russia

3 Department of Laser Optics, University ITMO, st. Petersburg, Russia drew-v@yandex.ru

Abstract-We report on the optical power limiting phenomena in fluid systems containing binary hybrid photo­active agents on the platform of SWCNTs in fluid matrices.

Keywords-optical power limiting; hybrids; nano-sized photo­active agents; synergism

I. INTRODUCTION

Materials basing on the single-walled carbon nanotubes (SWCNTs) circumscribe a variety of condensed-state identities. Suspensions of non-covalently functionalized SWCNTs are admittedly superior candidates for working out practical materials for non-linear optical power limiting (OPL) of high-intensity laser irradiation. Parameters of the purpose phenomenon achieved so far are, however, insufficient for direct application feed-in. One of the conceivable strategies to augment the OPL performance would consist in devising hybrid structures, which could procure a plethora of energy and charge exchange mechanisms among photo-active moieties of such structures, thereby giving way to their synergistic catering for the OPL effect.

II. CHOICE OF OBJECTS AND METHODOLOGIES EMPLOYED

We address non-covalently functionalized SWCNTs combined with a photo-active agent from the list: fullerenes CGO introduced into the SWCNT's hollow, a dye (rhodamine 6G, porphirins and their oligomers), diades "fullerene + porphyrine" in the surfactant micro-environment of SWCNTs. We also check auto-synergistic phenomena in the bundled SWCNTs. One can has three predicaments among these hybrids, viz., 1) those with saturable absorbers (SA) -rhodamine; 2) reverse saturable ones (RSA) - porphyrins, their oligomers and fullerenes; and 3) variously bundled SWCNTs with photo-induced scattering. Optical properties were studied using spectroscopy of absorbance, Raman scattering and luminescence; Cryo-TEM; monitoring of reciprocal "transmission vs. incident energy of laser light" and z-scanning with an open aperture.

III. COMPENDIUM OF RESULTS AND INFERENCES

The observations show weakening of the SWCNTs luminescence and non-linear OPL in their aqueous suspensions alongside reduction of bundle average diameters. We attribute

it to a growth in defectiveness of grapheme surfaces stemming from a growth of ultra-sonication duration. Introduction of a dye with saturable absorption into micro-environment of a SWCNT demonstrates positive synergism with respect to non­linear OPL (reduction of the limiting threshold and a growth of limiting coefficient). A pre-requisite for these manifestations we attribute to the adsorption of a dye on the SWCNT surface. Hybrids of SWCNTs with photo-active molecules manifesting RSA effect are prone for negative synergism regarding laser irradiation in the spectrum interval proximate to the domain of the RSA excitation. At the same time they can exhibit positive synergism in other spectrum intervals, the phenomenon being pre-determined with different mechanisms of re-distribution of the light energy.

The hybrid systems viewed provide guidelines for setting up limiting filters of laser irradiation in various wavebands.

ACKNOWLEDGMENT

Authors acknowledge support of Russian Foundation for Basic Research (grants # 14-02-00851 and # 13-03-01111). Further support was provided by the Government of Russian Federation (grant # 074-U01).

REFERENCES

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[2] A.Yu. Vlasov, AV. Venediktova, D.A. Videnichev, I.M. Kislyakov, E.D. Obraztsova, and E.P. Sokol ova, Phys. Stat. Solidi B, vol. 249, iss. 12, pp. 2341-2344, November 2012.

[3] I.M. Belousova, D.A. Videnichev, I.M. Kislyakov, AA. Ryzhov, O.B. Danilov, et aI., 1. Opt. Technol., vol. 80 iss. I, pp. 18-24, January 2013.