Nonlinear Optical Properties of Pure ZnO and Sn, Al Doped and Co-Doped ZnO Thin Films Using Z-Scan Technique.

The nonlinear optical (NLO) properties of pure and doped zinc oxide (ZnO) thin films, including those doped with tin (TZO), aluminum (AZO), and both aluminum and tin (ATZO), were studied using the Z-scan technique. These films were prepared using the spray pyrolysis technique. The results demonstrate that doping ZnO with aluminum (Al), tin (Sn), or both significantly influences the material's nonlinear absorption coefficient and nonlinear refractive index. Specifically, the nonlinear absorption coefficient (βeff) decreased for doped films from (5.294 cm/W) for pure ZnO film to (4.794 cm/W) for ATZO. Additionally, the nonlinear refractive index (n₂) was found to be negative for all films, were (n2) increased from (-2.237 x 10-9 cm2/W) for pure ZnO film to (-1.995 x 10-9 cm2/W) for ATZO. The real, the imaginary parts of the nonlinear susceptibility and the third-order (NLO) susceptibility was also found. These results highlight how doping could improve ZnO thin film nonlinear optical performance.