Synthesis of symmetric ionic liquids and their evaluation of nonlinear optical properties

The synthesis, functionalization and anion-exchange of symmetric ionic liquids (SILs) and their nonlinear optical studies are reported. Imidazolium cation was obtained in 75–99% of yield by condensation reaction (Debus-Radziszewski) using different amine derivatives and employing inorganic and organic acid as catalyst. The nonlinear optical properties were evaluated by Z scan technique, at 514 nm of Ar laser, where the symmetric ionic liquid showed a nonlinear optical effect. The values of n2 are of the order ~10−8 cm2/W, while β value is 10−5 cm/W. The nonlinear refractive index increases due to the high concentration, symmetric structures and non-aliphatic chains. On the other hand, the coefficient of nonlinear absorption increases at low concentrations with symmetric structures and aliphatic chains.