Nonlinear absorption of methylene blue solutions in the presence of plasmon nanoparticles with various surface charge

By continuous-pump Z-scanning, the nonlinear light absorption of aqueous and alcohol solutions of methylene blue was studied. It was shown that the mechanisms of optical nonlinearity of these solutions vary depending on the dye concentration and type of solvent. The dependence of the amplitude of nonlinear absorption of dye molecules on the concentration and sign of the surface charge of gold and silver nanoparticles in solution is revealed. Mathematical models of optical nonlinearity for concentrated and diluted solutions of dye molecules are considered; in the latter case, the influence of plasmon nanoparticles on the nonlinear optical characteristics of methylene blue solutions is taken into account