Yunfei Lv, Yuting Zhao, Fangyuan Shi, Zhongguo Li, Zhengguo Xiao, Xingzhi Wu, Zhongquan Nie, Quanying Wu, Yinglin Song, Yu Fang
Investigating the broadband nonlinear optical response and related dynamic mechanisms in the wide-bandgap semiconductor gallium oxide is crucial for ultrafast photonic applications. In this study, transient absorption spectroscopy was used to probe the metal-doping effect on the bound-electron nonlinear optical response. Fe doping was found to significantly enhance the nondegenerate two-photon absorption, a remarkably large imaginary component of the figure of merit, indicating potential applications for nonlinear absorption-based all-optical switching. Analysis of the optical polarization dependence of carrier absorption, combined with carrier-induced nonlinear refractive effect, demonstrated that Fe doping modulates the carrier lifetime and enables the transformation of phase symbols, establishing mechanisms for the implementation of dual-channel optical switching. An energy-level model based on photoluminescence elucidates the nonlinear optical modulation mechanism of Fe-related defect states on bound electrons and carriers. This study serves as a valuable reference for the design of gallium-oxide-based waveguides and all-optical switching materials.