We study the optical properties of an anisotropic ripple-shaped two-dimensional molybdenum disulfide (MoS₂) nanosheet deposited by chemical vapor deposition onto a nanopatterned silica (SiO₂) substrate. We unveil a giant anisotropic optical response in the linear and nonlinear regime by a combination of optical extinction measurements, ultrafast broadband transient absorption experiments, and finite element method numerical simulations. In steady state optical measurements, such anisotropy appears as a polarization-dependent extinction in correspondence with the characteristic excitonic peaks (A, B, C, and D) of MoS₂. Along with spectral changes, ultrafast measurements strikingly exhibit the onset of an anisotropic relaxation dynamic in the region of the C exciton. Numerical simulations indicate that the observed polarization-dependent optical response is dictated by the nanopattering of MoS₂, with peculiar features belonging to the out-of-plane component of the dielectric tensor of MoS₂ that is made effective through the rippled configuration. Our findings give a rationale to the anisotropic exciton response and show that morphology manipulation represents a valuable option for the tuning of optical and electronic properties in transition-metal dichalcogenides.

中文翻译：

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超快各向异性激子动力学的纳米图形的MoS ₂张

我们研究了通过化学气相沉积到纳米图案化的二氧化硅（SiO ₂）衬底上沉积的各向异性波纹状二维二硫化钼（MoS ₂）纳米片的光学特性。通过结合消光测量，超快速宽带瞬态吸收实验和有限元方法数值模拟，我们揭示了线性和非线性状态下的巨大各向异性光学响应。在稳态光学测量中，这种各向异性表现为偏振依赖性消光，与MoS ₂的特征激子峰（A，B，C和D）相对应。伴随光谱变化，超快测量在C激子区域显着展现了各向异性弛豫动力学的开始。数值模拟表明，观察到的偏振相关的光学响应是由MoS ₂的纳米图案决定的，其独特的特征属于MoS ₂的介电张量的平面外分量，该特征通过波纹配置有效。我们的发现为各向异性激子响应提供了理论基础，并表明形态学操纵是过渡金属二卤化物的光学和电子性质调节的宝贵选择。