The nonlinear optical properties of Acid black 1 in Chloroform solvent and polymer were studied using single beam Z-scan technique with a continuous-wave radiation at 635 nm of an output power of 40 mW. All the solution samples and polymer showed large nonlinear refractive indexice and absorption coefficient of the order of 10-7 cm2/W and 10-3 cm/W, respectively. The concentration-dependent nonlinear refractive index was also investigated. We presents experimental evidences of observing diffraction pattern in Acid black1: chloroform solvent with the calculation of the refractive index change, Δn , the relative phase shift, DF , and effective nonlinear refractive index ,n2. The solvent of spectroscopic grade and was used without further purification. All the solutions used for the study were freshly prepared.
