Investigating the optical nonlinear properties and limiting optical of eosin methylene blue solution using a cw laser beam

Diffraction patterns and Z-scan methods are used to measure the nonlinear refractive index, NRI, of the eosin methylene blue in the solvent ethanol using a continuous wave laser beam of 473 nm wavelength. Experimental results of the former and latter methods showed the appearance of rings and the self-defocusing SDF effect respectively, and these results may be due to phase modulation. It is demonstrated that the eosin methylene blue solution have a high NRI. Also the limiting optical properties of the sample are investigated. It is observed that the sample has the optical limiter properties OLPs. It is proved that the origin of the OLPs is thermal. The NRI and threshold limiting values of the eosin methylene blue solution are −1.1 × 10⁻⁸ cm² W⁻¹ and 12 mW, respectively. A thermal lens model and the Fresnel–Kirchhoff integral are used to calculate the self-defocusing and the diffraction ring patterns results respectively