The investigation of nonlinear optical limiting by aqueous suspensions of carbon nanoparticles

The mechanisms of nonlinear optical limiting by aqueous suspensions of nanometric size carbon particles are theoretically and experimentally investigated. At moderate densities of laser radiation energy, nonlinear limiting can be explained by light absorption in particles, their heating, the explosive boiling of surrounding liquid, the formation of vapor shell around particles, and light scattering by the expanding vapour shell. Scattering plays the predominant role in nonlinear optical limiting in comparison with absorption. The numerical modeling shows the existence of nonlinear light scattering in aqueous suspensions of carbon particles in wide spectral range 400-1060 nm (for pulse durations of about 10 ns). The results of numerical modeling were validated experimentally at two wavelengths within this range 1064 and 532 nm (first and second harmonic of Nd:YAG laser correspondingly). The numerical modeling shows that nonlinear light scattering efficiency falls with pulse duration shortening. (C) 2004 Elsevier B.V. All rights reserved.