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| 基于太赫兹扫描近场光学显微技术的探针优化策略 |
| Probe optimization strategy based on terahertz scanning near-field optical microscopy |
| 投稿时间：2025-02-19 |
| DOI：10.3969/j.issn.1005-5630.202502190027 |
| 中文关键词: 太赫兹散射式扫描近场光学显微镜 太赫兹纳米光谱成像 太赫兹近场探针 二维材料 太赫兹纳米光谱 |
| 英文关键词:terahertz scattering-type scanning near-field optical microscope THz nanospectral spectroscopy imaging THz near-field probe two-dimensional materials THz nano spectroscopy |
| 基金项目:国家自然科学基金（62422510，62301319）；上海市科委地方院校能力建设计划项目（23010503400） |
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| 中文摘要: |
| 太赫兹散射式扫描近场光学显微镜（terahertz scattering-type scanning near-field optical microscopy，THz s-SNOM）是表征材料载流子动力学、晶格振动及相变等光学和材料性质的关键技术。然而，THz s-SNOM较低的信噪比在一定程度上限制了其广泛应用，这一问题在低频太赫兹区域（＜ 2 THz）尤为突出。本研究针对0.5～1.5 THz波段下THz s-SNOM信噪比低的问题，通过实验与理论模拟相结合，系统探究了不同几何参数的定制化近场探针对THz s-SNOM信号强度的影响。研究结果表明：通过增大原子力显微镜探针针尖末端尺寸，可显著增强0.5～1.5 THz宽频范围内的近场散射信号。本研究进一步揭示，近场探针末端的散射偶极矩是决定THz s-SNOM信号强度的关键机制，并明确了探针几何参数与近场信号之间的定量关系。基于优化后的近场探针，实现了石墨烯/溴硫铬异质结体系的太赫兹纳米成像与纳米光谱测量。结果表明，与石墨烯在太赫兹波段表现出的金属性不同，溴硫铬在该频段呈现电介质行为。本工作提出的探针优化策略突破了现有THz s-SNOM技术的灵敏度限制，为高性能太赫兹近场光学探针的设计提供了理论依据，对推动纳米光子学表征技术的发展具有重要意义。 |
| 英文摘要: |
| Terahertz scattering-type scanning near-field optical microscopy (THz s-SNOM) is a key technique for characterizing the optical and material properties of functional materials, including carrier dynamics, lattice vibrations, and phase transitions. However, the low signal-to-noise ratio of THz s-SNOM has limited its widespread application to some extent, which is particularly severe at low-frequency THz regimes (＜2 THz). Therefore, effectively improving the signal-to-noise ratio of THz s-SNOM has become a critical issue that urgently needs to be addressed. This study focuses on the low signal-to-noise ratio issue of THz s-SNOM operating at 0.5–1.5 THz. By combining experiments and theoretical simulations, the influence of customized near-field probes with different geometric parameters on the signal intensity of THz s-SNOM was systematically investigated. The results indicate that increasing the apex size of the AFM probe can significantly enhance the near-field scattering signal over a broad frequency range of 0.5–1.5 THz. We further revealed that the scattering dipole moment at the tip apex was the key mechanism determining the THz s-SNOM signals intensity, and clarified the quantitative relationship between the probe geometric parameters and the near-field signal. Based on the optimized near-field probes, we further achieved THz nanoimaging and nanospectroscopy measurements of the graphene/CrSBr heterojunction. The results demonstrate that CrSBr exhibits dielectric behavior, which is distinct from the metallic response of graphene in the THz frequency region. The probe optimization strategy proposed in this work not only breaks through the sensitivity limitations of existing THz s-SNOM technology, but also provides a theoretical guidance for the design of high-performance THz near-field probes. This work is of great significance for promoting the advancement of nanophotonic characterization technologies. |
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