Study of molecular aggregation effects on the nonlinear refractive index and absorption of Oxazin 720 laser dye

Abstract

In this experimental work, nonlinear optical properties of Oxazine 720 laser dye in acetone, dimethyl sulfoxide, ethanol, and water were studied using the z-scan method. It is found that the nonlinear behavior of Oxazine 720 dye in water is different from other organic solvents. The magnitude of the nonlinear refractive index was obtained in the order of 10−8 and 10−7 cm2/W for the 0.2 mmol/L solutions of this dye in water and other solvents, respectively. Also, it was observed that, in the aqueous solution, reverse saturation absorption occurs while, in other organic solvents, saturation absorption occurs and, near the focal point of the lens, it is converted to reverse saturation absorption. These differences in the nonlinear refractive index and nonlinear absorption changes of aqueous solution and other solutions may be due to strong aggregative behavior of dye molecules in water.