Exploring nanoscale material properties through light-matter interactions is essential to unveil new phenomena and manipulate materials at the atomic level, paving the way for ground-breaking advancements in nanotechnology and materials science. Various elementary excitations and low-energy modes of materials reside in the terahertz (THz) range of the electromagnetic spectrum (0.1–10 THz) and occur over various spatial and temporal scales. However, due to the diffraction limit, a slew of THz studies are restricted to drawing conclusions from the spatially varying THz responses around half of the probing wavelengths, i.e., from tens to a couple of hundred micrometers. To address this fundamental challenge, scanning near-field optical microscopy (SNOM), notably scattering-type SNOM (s-SNOM), combined with THz sources has been employed and is fueling growing interest in this technique across multiple disciplines. This review (1) provides an overview of the system developments of SNOM, (2) evaluates current approaches to understand and quantify light-matter interactions, (3) explores advances in THz SNOM applications, especially studies with THz nano-scale spatial responses employing an s-SNOM, and (4) envisions future challenges and potential development avenues for the practical use of THz s-SNOM.

中文翻译：

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太赫兹纳米镜：进展、挑战和未来的道路

通过光与物质相互作用探索纳米级材料特性对于揭示新现象和在原子水平上操纵材料至关重要，从而为纳米技术和材料科学的突破性进展铺平道路。材料的各种基本激发和低能模式位于电磁频谱（0.1-10 THz）的太赫兹（THz）范围内，并发生在不同的空间和时间尺度上。然而，由于衍射极限，大量太赫兹研究仅限于从一半探测波长（即从几十到几百微米）空间变化的太赫兹响应中得出结论。为了解决这一基本挑战，扫描近场光学显微镜 (SNOM)，特别是散射型 SNOM (s-SNOM)，与太赫兹源相结合已被采用，并激发了跨学科对该技术日益增长的兴趣。本综述 (1) 概述了 SNOM 的系统发展，(2) 评估了当前理解和量化光与物质相互作用的方法，(3) 探讨了太赫兹 SNOM 应用的进展，特别是采用太赫兹纳米级空间响应的研究(4) 展望太赫兹 s-SNOM 实际应用的未来挑战和潜在发展途径。