Large third-order nonlinear optical susceptibility in high-entropy perovskite oxide thin films prepared by pulsed-laser deposition

Materials with excellent nonlinear optical properties are critical for advancing optoelectronic technologies, particularly in energy storage and ultrafast photonic devices. High-entropy perovskite oxides (HEPOs) have emerged as promising candidates due to their chemical stability and configurational complexity. In this work, HEPO thin films, (<i>L</i><i>a</i>_0.2<i>B</i><i>a</i>_0.2<i>S</i><i>r</i>_0.2<i>C</i><i>a</i>_0.2<i>B</i><i>i</i>_0.2)(<i>T</i><i>i</i>_1-<i>x</i><i>S</i><i>n</i>_<i>x</i>)<i>O</i>₃, were fabricated using the pulsed-laser deposition technique. The effects of configurational entropy-driven lattice distortion and multication synergy at both A- and B-sites on the third-order nonlinear optical response were systematically investigated. The optical transmission spectra in the visible-near infrared region were measured to demonstrate that the transparency of the films gradually increases with the increasing B-site Sn doping concentration. Z-scan measurements revealed that the optimized sample with <i>x</i>=0.5 exhibited a large third-order nonlinear susceptibility (<i>χ</i>⁽³⁾=1.36×10^-6<i>e</i><i>s</i><i>u</i>), accompanied by a record figure of merit (<i>χ</i>⁽³⁾/<i>α</i>=1.37×10^-8<i>e</i><i>s</i><i>u</i>⋅<i>c</i><i>m</i>). These results highlight the superior nonlinear optical performance of HEPOs, providing a foundation for practical applications in optical switches, optical limiters, and other optoelectronic devices.