Thickness-dependent nonlinear optical properties of ITO thin films

Abstract

The nonlinear absorption (NLA) properties of ITO thin lms were performed by utilizing femtosecond (100 fs), a high-repetition rate (80 MHz), and near-infrared (NIR) (750-820 nm) laser pulses. A radio frequency (RF) magnetron sputtering system was used to prepare ITO thin lms of two different thicknesses. A scanning electron microscope (SEM) was used to determine the lm thickness, and a UV-Visible spectrophotometer was used to observe the linear optical properties of the thin lms. The open aperture Z-scan technique's nonlinear absorption studies of ITO thin lms exhibited a reverse saturable absorption. The NLA properties of the ITO lms varied depending on ITO thickness, incident laser power, and excitation wavelength, attributed to the increasing localized defect states in the band gap. The nonlinear absorption coe cient of 6×10 − 7 cm/W and 9.7×10 − 7 cm/W were measured for 170 and 280 nm lm thicknesses, respectively. In contrast to the lm thickness, the nonlinear absorption coe cient was inversely proportional to the excitation laser wavelength. Additionally, the optical limiting of ITO thin lms was investigated, and it was found that there is a clear correlation between optical limiting and thin lm thickness.