Defect‐Induced Non‐Linear Optical Studies of Chromium‐Doped Strontium Tungstate Nanostructures

This research delves into the dopant effect on the non-linear optical properties of pristine SrWO4 nanostructures, utilizing the Z-scan technique, which employs Nd: YAG nano pulsed laser. 5 % of Cr-doped samples exhibit a high non-linear absorption coefficient value with good power limiting capacity. The 15 % Cr-doped SrWO4 demonstrates a notable behavior of transition from reverse saturable absorption to saturable absorption. The Z-scan technique was employed to inspect the non-linear optical characteristics of pristine and chromium-doped SrWO4 nanostructures. All of the samples′ scheelite-type tetragonal structure is revealed by structural analyses using X-ray diffraction (XRD), and no extra chromium impurity peaks are visible. The functional groups and the localized system were examined by using FTIR and Raman spectra analysis. Information about the energy transitions and the localized defect states was investigated by using photoluminescence studies. The morphological nature of pristine and doped samples was scanned by SEM and HR-TEM techniques. The linear properties are explored by the UV-visible absorption spectrum and the band gap values were found to be 4.84, 3.70, 3.24, and 2.50 eV for pristine and Cr-doped SrWO4 nanoparticles. The non-linear optical study was done by using Nd: YAG laser pulses at 532 nm. Here pristine SrWO4, 5 %, and 10 % Cr-doped SrWO4 nanostructures exhibit reverse saturable absorption (RSA) while 15 % Cr-doped SrWO4 nanostructures exhibit saturable absorption (SA) behavior. The calculated non-linear absorption coefficient values are high for 5 % of Cr-doped SrWO4 nanostructures due to the doping effect of chromium ions. Intensity-dependent Z-scan studies show 5 % Cr-doped SrWO4 sample exhibit sequential two-photon absorption. This changeover behavior of reverse saturable absorption to saturable absorption of Cr-doped SrWO4 samples at higher concentrations opens the path to use this material in optical limiting and optical switching applications. The authors declare no conflict of interest. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.