الفهرس 
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Abstract
The main objective of this dissertation is to study the interaction of ultrashort laser pulses with material with real permittivity close to zero, also known as epsilon-near-zero (ENZ). Because of their remarkable nonlinear optical (NLO) properties, especially in frequency ranges where the material is transferring from dielectric to metal, ENZ materials have become a topic of interest. My dissertation aims to investigate transparent conducting oxides (TCO) like Indium Tin Oxide (ITO) as a promising material for displaying the ENZ condition and using this effect NLO devices.
Third-order nonlinear optical (NLO) properties of ITO thin films were studied using laser pulses with a high repetition rate (80 MHz), femtosecond (100 fs), and near-infrared (NIR) wavelengths (750–820 nm). Radio frequency (RF) magnetron sputtering was used to prepare ITO thin films on a glass substrate at room temperature. Then, characterization of the coated ITO thin films was carried out. The film thickness was measured by using a scanning electron microscope (SEM), the structure and crystallinity of films were examined by X-ray diffraction (XRD), the linear optical properties of the thin films were observed using a UV-Vis spectrophotometer, and the elemental analysis of ITO thin films was determined by energy dispersive X-ray (EDX).
Thermal nonlinear properties influenced by laser parameters and ITO thin films, such as nonlinear refractive index (NLR), nonlinear absorption coefficient (NLA), and thermo-optic coefficient (dn/dT), are measured using the sensitive technique. Because of its simplicity and sensitivity, the Z-scan method is the most widely used technique for measuring nonlinear parameters. The optical Kerr nonlinearity of ITO thin films of different thicknesses was investigated at different excitation wavelengths and incident pulse energies. The optical Kerr nonlinearity was found to be dependent on the excitation wavelength, incident power, and ITO thickness, with a maximum value of ” ” ” ” ” " ~ " ” ” ” ” ”9×10−12 cm2/W at a wavelength of 820 nm, power of 1 W, and 170 nm ITO thickness. These results suggest that Kerr nonlinearity in ITO can be tailored by varying the film thickness, which would be ideal for ultrafast all-optical switching in future optoelectronic devices.
NLA studies of ITO thin films utilizing the open aperture (OA) Z-scan technique exhibited that the transition from RSA to RSA-SA-RSA switching behavior was influenced by ITO thickness. The NLA properties of the ITO films changed depending on ITO thickness, incident laser power, and excitation wavelength, which was attributed to the increasing localized defect states in the band gap. A saturation model has been used to explain the observed saturation of two-photon absorption (2PA) at high incident powers. The NLA coefficient was shown to be inversely proportional to the excitation power and wavelength.
Because of their high third-order nonlinear optical responses, these ITO thin films are ideal candidates for photonic applications. Furthermore, the optical limiting of ITO thin films was investigated, and a direct relationship between thin film thickness and optical limiting was observed.