ABSTRACT Bi 2 O 2 Se nanoplates, a semiconductor saturable absorber (SA) characterized by strong nonlinear absorption and excellent stability, are typically hindered by scattering losses introduced during defect modulation. In this study, by combining with a non‐metallic semiconductor WO 3‐x , the WO 3‐x /Bi 2 O 2 Se plasmonic heterostructure is developed to sufficiently overcome the aforementioned limitations. The as‐developed heterostructure SA is applied for 1040 nm Yb,Y:CaF 2 ‐SrF 2 mode‐locked lasers, realizing ultrashort pulses of ∼364 fs at a significantly reduced absorbed pump threshold of 2.02 W and an average output power of 424 mW. Finite‐difference time‐domain (FDTD) simulations, transient absorption spectroscopy, and open‐aperture Z‐scan measurements collectively reveal that hot‐carrier transfer mediated by localized surface plasmon resonance significantly promotes Auger recombination in Bi 2 O 2 Se, thereby shortening carrier lifetimes. This effect is particularly pronounced at 1050 nm, manifesting as a substantial increase in the nonlinear absorption coefficient from −(507 ± 4) to −(1587 ± 14) cm MW −1 . The resultant plasmon‐enhanced nonlinear optical response facilitates the realization of ultrafast pulses from a mode‐locked laser operating at lower thresholds and narrower pulse widths.
Liu et al. (2026) studied this question.