Investigations on nonlinear optical properties of electron beam treated Gd: ZnO thin films for photonic device applications

In this article, we report the third-order nonlinear optical properties of electron beam irradiated gadolinium-doped zinc oxide (GZO) thin films prepared using the spray pyrolysis deposition technique. GZO thin films were treated with an electron beam from a variable energy microtron accelerator at dose rates ranging from 1-5 kGy. Nonlinear optical measurements were conducted by employing the single beam Z-scan technique. A continuous wave He-Ne laser operating at 633 nm was used as the source of excitation. Closed aperture Z-scan results reveal that the films exhibit self-defocusing nonlinearity. Open aperture Z-scan results exhibit a switching over phenomena of reverse saturable absorption to saturable absorption for thin film irradiated at 3 kGy, indicating the influence of electron beams on optical nonlinearity. The significant change in third-order nonlinear optical susceptibility χ⁽³⁾ ranging from 2.14 × 10^-3 to 3.12 × 10^-3 esu is attributed to the effect of electron beam irradiation. The study shows that the nonlinear coefficients of GZO films can be tuned by electron beams for use in nonlinear optical device applications.