Comparison study of the structure, dielectric function, and two-photon absorption cross-section of BiOI and Ag/BiOI nanomaterials

In this research, the interesting methods including X-ray diffraction (XRD) pattern, Field Emission Scanning Electron Microscopy (FESEM) images, energy dispersive X-ray (EDX), UV–Vis spectroscopy, Diffuse reflectance (DRS) spectrum, KK method, and Z-scan measurements were employed for characterizations of prepared BiOI and Ag/BiOI nanomaterials. The optical indices such as n, k, and ε1 and ε2 were assessed based on reflectance spectra data and the Kramers-Kronig (KK) method. Furthermore, the nonlinear optical (NLO) properties of prepared BiOI and Ag/BiOI nanomaterials in different Ag precents were examined through the Z-scan method using the laser beam at 532 nm wavelength. The two-photon absorption (TPA) and self-focusing performance are revealed by the prepared nanomaterials. Adding Ag into BiOI structures, significantly increases the TPA cross-section, σ2 which reaches up to 1.14578 × 10−21 cm4/W for the sample of S3. One of the significant factors that affected the improvement of the optical nonlinearity properties of Ag/BiOI and over BiOI was ascribed to the combined consequence of Ag's localized surface plasmon resonance (LSPR) phenomena, resulting in improved light absorption intensity coupling interaction, significant photo-produced electron-hole separability, and prolonged carrier lifetime.