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

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, (La_0.2Ba_0.2Sr_0.2Ca_0.2Bi_0.2)(Ti_1-xSn_x)O₃, 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 x=0.5 exhibited a large third-order nonlinear susceptibility (χ⁽³⁾=1.36×10^-6esu), accompanied by a record figure of merit (χ⁽³⁾/α=1.37×10^-8esu⋅cm). 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.