Abstract Nonlinear absorption of multi-layer black phosphorus nanosheets (BPs) were investigated using open aperture Z-scan method with 6 ns nanosecond laser pulses at 532 nm. It was found that, at lower intensities, BPs behave as saturable absorbers, but at higher intensities a shift from saturable absorption to reverse saturable absorption occurs. The transition process was analyzed in terms of the bleaching of ground-state and the excited-state absorption. We investigate the ultrafast dynamics by using pump − probe technique. The investigation implies that BPs has great potential applications in both mode-locking and optical liming in the visible range for ultrafast laser pulses.

中文翻译：

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黑磷光非线性吸收的转换

摘要 使用532 nm 6 ns 纳秒激光脉冲的开孔Z 扫描方法研究了多层黑磷纳米片(BPs) 的非线性吸收。发现，在较低强度下，BPs 表现为可饱和吸收剂，但在较高强度下，会发生从饱和吸收到反饱和吸收的转变。从基态漂白和激发态吸收两个方面分析了跃迁过程。我们通过使用泵 - 探针技术研究超快动力学。研究表明，BPs 在超快激光脉冲的可见光范围内的锁模和光学照明方面具有巨大的潜在应用。