  This work describes the experimental and theoretical study of the nonlinear
optical properties of the imidazolium cation based ionic liquids and the
corresponding thermo-optical parameters. Experimental results of nonlinear
optical properties, such as nonlinear refractive index and thermo-optical
properties are determined by Z-scan and EZ-scan techniques with a femtosecond
laser source. Theoretical simulations of linear and nonlinear optical
properties performed by density functional theory (DFT) are discussed, in terms
of polarizability, the first and second-order of hyperpolarizability. A
correlation between the theoretical and experimental results is presented,
where the variation of the signals of each ionic liquid can be compared with
their nonlinear optical properties.
