Abstract
In this paper the nonlinear optical properties of Co-doped ZnO and pure ZnO thin films were measured. The films were irradiated with 100 femtosecond laser pulses at 950 nm and at different input intensities ranging from 9 to ${14}\;{{\rm GW/cm}^2}$. We observed that two-photon absorption induced a reverse saturable absorption and saturable absorption in Co-doped ZnO, while the three-photon absorption was observed to induce saturable absorption in pure ZnO. The nonlinear absorption coefficient $\beta$ and nonlinear refractive index ${{n}_2}$ of Co-doped ZnO were found to be intensity dependent. An enhancement of 100 times in the nonlinear refractive index was observed for the Co-doped ZnO thin films compared to pure ZnO thin films. This reveal a strong optical limiting behavior for the Co-doped ZnO in comparison to pure ZnO thin films.
© 2020 Optical Society of America
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