Silver (Ag) nanoparticle-decorated zinc oxide (ZnO) nanowires (Ag–ZnO) have been successfully synthesized by chemical vapour deposition and the magnetron sputtering method. Scanning electron microscopy images indicate that Ag nanoparticles are distributed uniformly on the surface of the ZnO nanowires. The results of room temperature photoluminescence (RTPL) reveal two major emission peaks for the Ag–ZnO nanowires, and the emission peaks in the visible region are stronger than those of the unmodified ZnO nanowires. The mechanism of RTPL and low temperature photoluminescence (LTPL) emission is discussed in detail. Nonlinear optical properties and ultrafast dynamics have been investigated using the Z-scan and two color pump–probe (TCPP) techniques, respectively. The nonlinear absorption properties in the nano-, pico- and femto-second regime have been analyzed using the singlet state three-level and four-level models, respectively. The samples show self-focusing nonlinearity and good two-photon absorption (TPA)-induced ground state saturation absorption as well as excited state reverse saturable absorption behavior. For the nanosecond and picosecond pulses, the reverse saturated absorption in the excited state mainly originates from the absorption at low excited states or deep levels; however, for the femtosecond pulse, it is caused by the absorption at high excited states. The TCPP results show that the ground state or deep level light bleaching (for nano- and pico-second regime) and TPA-induced excited-state absorption (for femtosecond regime) behaviors range from 470 nm to 620 nm. The remarkable nonlinear optical properties reveal that Ag–ZnO nanowires are potential nanocomposite materials for the development of nonlinear optical devices.

中文翻译：

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银纳米粒子修饰的氧化锌纳米线的超快非线性光学性质和载流子动力学

通过化学气相沉积和磁控溅射法成功合成了银（Ag）纳米颗粒装饰的氧化锌（ZnO）纳米线（Ag-ZnO）。扫描电子显微镜图像表明，Ag 纳米颗粒均匀分布在 ZnO 纳米线的表面。室温光致发光（RTPL）结果揭示了 Ag-ZnO 纳米线的两个主要发射峰，可见光区的发射峰比未改性的 ZnO 纳米线强。详细讨论了 RTPL 和低温光致发光 (LTPL) 发射的机理。非线性光学特性和超快动力学已经使用Z进行了研究-scan 和两种颜色泵探头 (TCPP) 技术，分别。分别使用单重态三能级和四能级模型分析了纳秒、皮秒和飞秒范围内的非线性吸收特性。样品显示出自聚焦非线性和良好的双光子吸收（TPA）诱导的基态饱和吸收以及激发态反向饱和吸收行为。对于纳秒和皮秒脉冲，激发态的反向饱和吸收主要来源于低激发态或深能级的吸收；然而，对于飞秒脉冲，它是由高激发态的吸收引起的。TCPP 结果表明，基态或深能级光漂白（对于纳秒和皮秒范围）和 TPA 诱导的激发态吸收（对于飞秒范围）行为范围为 470 nm 至 620 nm。显着的非线性光学特性表明，Ag-ZnO 纳米线是用于开发非线性光学器件的潜在纳米复合材料。