The saturable absorption properties of BiOI nanosheets with exposed {110} facets prepared by the chemical vapor transport were investigated by Z-scan with femtosecond pulse laser. The nonlinear absorption coefficient at 400 nm is stronger and more sensitive to photoexcitation than its nonlinear response at 800 nm. The small saturation intensity could have been achieved, which is one order of magnitude smaller than that of black phosphorus nanosheets, while the ${\rm Im}{\chi ^{(3)}}$ are determined to be $-{4.35} \times {{10}^{- 12}}\;{\rm esu}$ close to theoretical prediction. According to time-resolved photoluminescence spectrum results, this strong saturated absorption at 400 nm may be attributed to the interband recombination process, whose lifetime was 230 ps.

中文翻译：

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通过化学蒸汽传输制备的 BiOI 纳米片的超快饱和吸收

通过使用飞秒脉冲激光的 Z 扫描研究了通过化学蒸汽传输制备的具有暴露的 {110} 面的 BiOI 纳米片的饱和吸收特性。400 nm 处的非线性吸收系数比 800 nm 处的非线性响应更强，对光激发更敏感。可以实现小的饱和强度，这比黑磷纳米片小一个数量级，而${\rm Im}{\chi ^{(3)}}$被确定为$-{4.35 } \times {{10}^{- 12}}\;{\rm esu}$接近理论预测。根据时间分辨光致发光光谱结果，这种在 400 nm 处的强饱和吸收可能归因于带间复合过程，其寿命为 230 ps。