层状 ZrTe5 中的完全各向异性超快光开关和方向相关光载流子扩散,Advanced Optical Materials

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层状 ZrTe5 中的完全各向异性超快光开关和方向相关光载流子扩散
Advanced Optical Materials ( IF 8.0 ) Pub Date : 2022-12-01 , DOI: 10.1002/adom.202201544
Sung Bok Seo ₁ , Sanghee Nah ₂ , Muhammad Sajjad ₃ , Jiacheng Song ₁ , Nirpendra Singh _{3,

4} , Sang Ho Suk ₁ , Hionsuck Baik ₂ , Sanghoon Kim ₅ , Geun‐Ju Kim ₅ , Jung‐Il Kim ₅ , Sangwan Sim ₁

Affiliation

具有面内各向异性的层状纳米材料对外部刺激表现出独特的方向依赖性响应，从而能够开发具有额外自由度的新型设备。特别是，它们的各向异性光学特性使超快纳米光子调制器能够通过光偏振来控制。然而，由于大多数材料的光学各向异性不完全，实现高可控性仍然具有挑战性。在这里，这项工作在五碲化锆 (ZrTe ₅)，一种层状纳米材料，最近引起了新的关注。瞬态吸收 (TA) 显微镜揭示了 1.2–2.2 eV 宽范围内的各向异性超快皮秒光学调制。特别地，在 1.62 eV 的特定光子能量下，仅通过改变光偏振就可以实现具有接近统一程度的各向异性的完全开/关切换，这表明 ZrTe ₅是一种很有前途的偏振选择性高速光调制器材料。跃迁偶极矩的理论分析将这种尖锐的各向异性归因于强烈的偏振相关激发态吸收。此外，这项工作使用扫描 TA 显微镜直接观察方向相关的光载流子传输。它产生光载流子的各向异性扩散率、迁移率和扩散长度，这些是设计器件的基本参数。_{因此，这项工作提供了对 ZrTe 5}在超快时间尺度上的各向异性光学特性的全面了解。

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Completely Anisotropic Ultrafast Optical Switching and Direction-Dependent Photocarrier Diffusion in Layered ZrTe5

Layered nanomaterials with in-plane anisotropy exhibit unique orientation-dependent responses to external stimuli, enabling the development of novel devices with additional degrees of freedom. In particular, their anisotropic optical properties enable ultrafast nanophotonic modulators to be controlled by light polarization. However, achieving high controllability is still challenging due to incomplete optical anisotropy in most materials. Here, this work presents a completely anisotropic, ultrafast optical modulation in zirconium pentatelluride (ZrTe₅), a layered nanomaterial that has recently attracted renewed attention. The transient absorption (TA) microscopy reveals anisotropic ultrafast picosecond optical modulation in a broad range of 1.2–2.2 eV. In particular, at a certain photon-energy of 1.62 eV, complete on/off switching with a near-unity degree of anisotropy is achieved solely by changing the light polarization, suggesting that ZrTe₅ is a promising material for polarization-selective high-speed optical modulators. The theoretical analysis of the transition dipole moments attributes this sharp anisotropy to strongly polarization-dependent excited-state absorption. Furthermore, this work directly observes direction-dependent photocarrier transport using scanning TA microscopy. It yields the anisotropic diffusivity, mobility, and diffusion lengths of the photocarriers, which are essential parameters for designing devices. Therefore, this work provides a comprehensive understanding of the anisotropic optical characteristics of ZrTe₅ on ultrafast timescales.

更新日期：2022-12-01

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