The nonlinear optical absorption and optical limiting properties of noble metal-doped ZnO films

Herein, pure ZnO, Ag-doped ZnO, and Cu-doped ZnO films with excellent ultrafast (femtosecond) nonlinear absorption/limiting behavior were deposited on quartz substrates by magnetron sputtering. From the open-aperture Z-scan result, under femtosecond pulses, the strong two-photon absorption (TPA) behavior of metal-doped ZnO was found, and the absorption coefficient was found to be several times that of pure ZnO, which will expand the design and application strategies of metal-doped wide-gap semiconductor materials in the field of nonlinear devices. Moreover, the samples exhibited superior optical limiting behavior with respect to the optical modulation characteristics of the input–output laser. The mechanism of optical limiting effects is induced by the TPA-induced reverse saturable absorption of the deep level and low excited state processes.