Nonlinear optical properties and optical limiting performance of scandium doped Zinc oxide (SZO) thin films

The present work focuses on the preparation of films via Sol–gel method and to study their nonlinear optical properties. Optical systems are always under a threat of attack from high intensity laser radiations, under the exposure of which any optical detector or any optical system may be damaged. Optical Limiters have been designed to protect such devices from high intensity Laser attacks. The study is dedicated to optical limiting properties of Scandium Doped Zinc Oxide (SZO) thin films for various doping concentrations. Films with doping concentration 0.2 wt, 0.4 wt, 0.6 wt and 0.8 wt % were prepared through Sol–gel method. These films were annealed at 400 °C for 1 h. After annealing, structural properties were studied through XRD plots. Linear optical properties and optical band gap were studied through Tauc’s plots. Nonlinear Absorption Coefficient was calculated through Open Aperture Z-Scan with 5 ns Nd-YAG laser pulses at 532 nm. Nonlinear absorption Coefficient (β) was found to be 1.11 × 10^–8 to 1.55 × 10^–8 m/W. Nonlinear refraction Coefficient (n₂) and value of third-order susceptibility (χ³) were calculated through Closed Aperture Z-Scan using same laser source. The value of nonlinear refraction coefficient (n₂) varied from − 1.48 × 10^–12 to−2.04 × 10^–12 m²/W. The calculated value of third-order susceptibility (χ³) was found to be varying from 0.99 × 10^–22 to 4.23 × 10^–22 m²/V². Optical limiting threshold was found to be varying between 4.25 to 4.95 kJ/cm². The value of thermo-optic coefficient and focal length of the thermal lens for thin films of 0.6 wt. % were also calculated and comes out to be − 1.5 × 10^–9 K⁻¹ and−2.2 × 10^–6 m, respectively. These samples are good enough for nonlinearity and have practical application as potential material for optical limiter.