Low dimensional tellurium is currently of great interest for potential electronic applications due to the experimentally observed Weyl fermions and the excellent carrier mobility, on/off ratios and current-carrying capacity in devices. However, the optical properties of Te nanostructures are not well explored, especially in the field of nonlinear optics. Here, we prepared a series of Te nanostructures by electrochemical exfoliation and liquid phase exfoliation methods, including one-dimensional (1D) Te nanowires (NWs), quasi-1D Te nanorods (NRs), zero-dimensional (0D) Te nanodots (NDs) and two-dimensional (2D) Te nanosheets (NSs). Femtosecond Z-scan measurements reveal unique dimension-dependent nonlinear optical (NLO) properties. 1D Te NWs and quasi-1D Te NRs exhibited higher saturable absorption behavior than 0D Te nanostructures, while the 2D Te NSs are a high performance optical limiting material. Ultrafast transient absorption spectroscopy revealed the dimension-dependent exciton dynamics. The reverse saturable absorption of 2D Te NSs is derived from faster exciton relaxation and stronger excited state absorption. This work paves the way for the design of saturable absorbers with high performance and broadens the application of 2D Te in the field of laser protection and other novel ultrafast photonics.

中文翻译：

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揭示碲纳米结构飞秒非线性光学特性的尺寸依赖性

由于实验观察到的外尔费米子和出色的载流子迁移率、开/关比和器件中的载流能力，低维碲目前对潜在的电子应用非常感兴趣。然而，Te纳米结构的光学特性并没有得到很好的探索，特别是在非线性光学领域。在这里，我们通过电化学剥离和液相剥离方法制备了一系列 Te 纳米结构，包括一维（1D）Te 纳米线（NWs）、准一维 Te 纳米棒（NRs）、零维（0D）Te 纳米点（NDs） ) 和二维 (2D) Te 纳米片 (NSs)。飞秒 Z 扫描测量揭示了独特的尺寸相关非线性光学 (NLO) 特性。1D Te NWs和准1D Te NRs表现出比0D Te纳米结构更高的饱和吸收行为，而 2D Te NSs 是一种高性能的光学限制材料。超快瞬态吸收光谱揭示了尺寸相关的激子动力学。2D Te NSs 的反饱和吸收源于更快的激子弛豫和更强的激发态吸收。这项工作为高性能可饱和吸收体的设计铺平了道路，并拓宽了 2D Te 在激光保护和其他新型超快光子学领域的应用。