Studying of Nonlinear Optical Properties of Binary Bi2S3 and Bi2Te3/PMMA Nanocomposite Films by Z-Scan Technique

For measuring the nonlinear refraction index n₂ and absorption index β, we have used modified Z-scan technique with the single laser beam. The media is a nanocomposite films made from the binary (Bi₂S₃ and Bi₂Te₃) with PMMA. The material is prepared via the microwave-assisted chemical method. The Characterization of the nanocomposite films was carried out using X-ray diffraction (XRD), and U-V spectroscopy. The band gaps of Bi₂S₃ and Bi₂Te₃ are 2.6ev and 2.38ev respectively. XRD shows that Bi₂S₃ and Bi₂Te₃ have orthorhombic and trigonal (hexagonal axes) structures respectively. The optical non-linearity is intensity dependent. The nanocomposite films exhibit self-defocusing nonlinearity beneath the empirical conditions. Both samples exhibit a large negative nonlinear refractive index and good nonlinear absorption coefficient with increasing laser input power. The spotted nonlinear refraction and absorption are related to thermal in nature and reverse Saturable absorption, respectively. The obtained results indicate that the nanocomposite films may open several new possibilities of using these materials in all-optical element devices.