Third Order Nonlinear Optical Studies of ZnS Nanostructures Synthesized by Laser Ablation Technique

Abstract

We report the nonlinear optical (NLO) studies of ZnS nanostructures (NS) in polyvinyl pyrrolidone/dimethyl formamide (PVP/DMF) synthesized by laser ablation technique. We used a frequency doubled Q-switched Nd:YAG laser operating at 532 nm with a repetition rate of 10 Hz, 7 ns pulse width for ablation. The obtained nanoparticles showed a maximum absorption peak at 270.5 nm and were further chararacterized by Transmission Electron Microscope (TEM), X ray diffractometer (XRD), and Scanning Electron Microscope (SEM) from which the formation of NS was confirmed. The third order nonlinear optical susceptibility (χ⁽³⁾) of nanocomposite was measured using the single beam Z-scan technique. The mechanism behind the nonlinear absorption was confirmed to be two photon absorption (2PA) as the open aperture Z-scan curves of ZnS NS were fitted well to the theoretical model for 2PA. Also, the unvarying values of the nonlinear absorption coefficient (β_eff) with different on-axis input intensities endorse 2PA as the principal absorption mechanism. The χ⁽³⁾ value measured was 4.7 × 10⁻¹² esu which ensures its potential usefulness in photonic applications exploiting optical limiting property.