Solvent Effects on The Nonlinear Refractive Index of Bromocresol Purple at Three Excitation Wavelengths

Abstract

In this study, the linear properties and the nonlinear refraction of Bromocresol purple (BCP) dye are studied in water and ethanol at three different wavelengths (405, 473 and 532 nm). The study is to assess the effect of the solvent properties on the dye optical characteristics at different wavelengths. Beside the differences in the linear response, the nonlinear refractive index n 2 of the dye changes by changing the solvent. The type of the solvent-induced change in n 2 depends on the excitation wavelength. In addition, the value of n 2 in the same solvent depends on the wavelength of light. The changes in n 2 in the two solvents are not likely to be due to the differences in the linear absorption or the thermal effects. The polarity and the hydrogen bonding ability of the solvent can be the main reason of the solvent effects on the nonlinearity of the dye. The effect of wavelength on the nonlinearity of the dye can be due to the change in the physical mechanisms that originate the nonlinear refraction or the change in their individual contributions to the overall nonlinear refraction of the dye.