Irradiation-Resistant Two-Dimensional W₂N₃ as Efficient Saturable Absorbers: Implications for Space Use

Space exploration is inseparable from advanced antiradiation materials with exceptional properties. Among these, nonlinear optical materials and devices, such as irradiation-resistant saturable absorbers (SAs), have garnered significant attention, particularly due to their critical role in integrated photonics for space use. This study presents a comprehensive evaluation of the space adaptability of two-dimensional (2D) W₂N₃ under simulated space radiation conditions. When subjected to ⁶⁰Co γ-ray irradiation at doses exceeding 45 years of accumulation in a typical low-Earth orbit, W₂N₃ retained its robust third-order nonlinear saturable absorption across the visible- to near-infrared spectral range. Femtosecond transient absorption spectra offer a comprehensive view of the carrier dynamics of W₂N₃ before and after irradiation, delving into radiation effects and damage mechanisms that are otherwise elusive to conventional techniques. The synthesized W₂N₃ nanosheets were successfully employed as efficient SAs for Q-switched mode-locking in a Yb-doped fiber laser. The laser system operated at ∼1 μm NIR with high pulse energy and low saturation power, highlighting the remarkable potential of W₂N₃ for integration into lasers, modulators, and other photonic devices. Notably, the irradiated W₂N₃ demonstrated an identical mode-locking performance compared to its pristine counterpart. These findings provide valuable guidance for the rational design and screening of nonlinear optical materials capable of withstanding space radiation, offering significant implications for future space-based photonic applications.