DFT and Z-scan Studies for the Determination of Nonlinear Optical Susceptibility and Second Order Hyperpolarizability of Ethidium Bromide Dye in Different Solvents.

Nonlinear optical (NLO) susceptibility of Ethidium Bromide (EB) dye, an excellent NLO material, dissolved in different solvents, including ethanol, methanol, acetone, 1-propanol, DMF, and DMSO is reported. Z-scan tool is used to measure the NLO features of EB dye using open and closed aperture methods. The peak-valley transmittance graph indicating self-defocusing nonlinearity in the nonlinear refractive index of EB dye in different solvents. The nonlinear absorption coefficient showed both positive and negative nonlinearity is the result of saturable and reverse saturable absorption behavior from the open aperture curve. The absorption coefficient and nonlinear refractive index of EB dye in various solvents are found to be the order of 10^-4 m/W and 10^-11 m²/W, respectively. Significant second-order hyperpolarizability and third-order NLO susceptibility are observed in EB dye dissolved in DMSO. The effect of the solvent on the solute molecule is assessed using a multi-parameter scale that considered both specific and non-specific interactions. The investigation of NLO properties of EB dye is carried out using the DFT method at the B3LYP/6-311 + + G(d, p) level to compute the linear polarizability (α), first-order hyperpolarizability (β), and second-order hyperpolarizability (γ) values in different solvents. These theoretical findings are further supported by experimental results, highlighting the solvent-dependent enhancement of NLO properties.