Third-order optical nonlinearities of two-dimensional SnS under irradiation: implications for space use

Space exploration urgently demands novel irradiation-tolerant materials to build the arsenal for outer space use, among which nonlinear optical materials and devices are ever-increasing attractive. Tin sulfide (SnS), a novel two dimensional (2D) BP-analog with enhanced stability under ambient conditions, has exhibited excellent optoelectronic properties on the ground, but its potential as a candidate for space optics remains to be explored. Herein, the spatial adaptability of SnS was evaluated in the simulated space radiation environment. When exposed to Co-60 gamma-rays at a dose equal to over 45 year accumulation in a typical earth orbit, SnS still maintained its strong third-order nonlinear saturable absorption ranging from visible to near-infrared spectra. Ultrafast spectroscopy is used to study the radiation effects and relevant damage mechanisms that are difficult to be revealed via conventional techniques. This work not only sheds light on the irradiation-induced ionization damage and defects in SnS from the unique perspective of ultrafast excited state dynamics but also provides general guidance for rational design and screening space radiation-tolerant nonlinear optical materials.