Synthesis, characterization and determination of third-order optical nonlinearity by cw z-scan technique of novel thiobarbituric acid derivative dyes

•Two new chromophores are synthesized by Knovenagel reaction of Thiobarbituric acid, 9-ethyl-9H-carbazole-3-carbaldehyde and 3,4-dimethoxy benzaldehhde.•The obtained compounds named as T1 and T2 are stable in both crystalline and solution forms•They are characterized by optical absorption, fluorescence, 1H NMR, 13C NMR, FT-IR, MS spectroscopy and purity of the compounds is confirmed by elemental analyses.•Nonlinear optical properties are measured by z-scan technique with a cw He–Ne laser.•The chromophores show high values of nonlinear refractive index and nonlinear absorption coefficient and vary linearly with concentration.

Donor acceptor chromophores were prepared by Knovenagel reaction of 1,3-diethyl-2-thiobarbituric acid with corresponding aldehydes in ethanol using pyridine as catalyst. The structures of newly synthesized compounds were evaluated by FT-IR, 1H NMR, 13C NMR, MS spectroscopy and purity of the compounds were confirmed by elemental analyses. The nonlinear refractive index n2 and nonlinear absorption coefficient β are measured for these dyes using the closed and open aperture z-scan technique with a cw He–Ne laser at 632.8 nm. These values are found to be high and linearly dependent on the concentration.