Nonlinear optical properties in organic fish gelatin, potassium dichromate, and organic–inorganic mix

•We present a study of the nonlinear optical properties of fish gelatin, potassium dichromate, and their mix.•The experimental results are obtained by the Z-scan technique and analyzed with the thermal lens model (TLM).•We calculate the nonlinear refractive index and nonlinear absorption with a single experimental measurement.•To determine if the nonlinearity of the mixture increases, the electrostatic interaction between the materials is studied.•We use the density functional theory. The nonlinear optical properties of fish gelatin, potassium dichromate, and a mix of both are presented. The z-scan experimental technique and the photo-induced thermal lens formation model are used to determine nonlinear optical parameters such as the non-linear refractive index and the nonlinear optical absorption coefficient. The spatial self-phase modulation in the mixture is analyzed with an Ar continuous wave (cw) laser at 477 nm at different light powers. Furthermore, we theoretically studied the electrostatic interaction between potassium dichromate and fish collagen based on the Density Functional Theory. The experimental and theoretical results show that the nonlinear optical properties of the mixture are improved due to better thermal conductivity and stability, indicating a high potential for optical applications such as nonlinear gratings and holography.