Choi Da-Hye
Terahertz Research Section, Electronics and Telecommunications Research Institute, Deajeon, 34129, Republic of Korea.
Sci Rep. 2025 Jan 7;15(1):1137. doi: 10.1038/s41598-025-85259-w.
The complex dynamics of terahertz (THz) wave scattering by subwavelength-scale structures remain largely unexplored. This article examines the spectral scattering characteristics of subwavelength-sized spherical particles probed by tightly focused THz waves through numerical simulations and experimental techniques. The simulations reveal that the scattering intensity for lower Mie resonance modes (magnetic dipole and electric dipole modes) remains largely unaffected when THz waves are focused down to 0.3 λ, whereas higher Mie resonance modes experience a significant decrease in intensity as the beam size is reduced. Experimentally, scattering effects were observed by imaging two subwavelength-sized dielectric spheres, each with a diameter of 480 μm and refractive indices of 2 and 6, around 0.3 THz, where the magnetic dipole mode of the particle with refractive index of 2 was detected. Experimental results confirm that the image contrast of the spheres is predominantly influenced by scattering effects near the Mie resonance frequency, even with low refractive index materials. This work represents a significant advancement in the detection and characterization of subwavelength-sized structures within the THz region. Furthermore, the findings extend beyond THz frequency ranges and have potential applications in fields such as sensing, imaging, and sizing across optical, infrared, and millimeter wave ranges.
太赫兹（THz）波在亚波长尺度结构上散射的复杂动力学在很大程度上仍未得到探索。本文通过数值模拟和实验技术研究了紧密聚焦的太赫兹波探测的亚波长尺寸球形颗粒的光谱散射特性。模拟结果表明，当太赫兹波聚焦到0.3λ时，较低的米氏共振模式（磁偶极子和电偶极子模式）的散射强度基本不受影响，而随着光束尺寸减小，较高的米氏共振模式的强度会显著降低。在实验中，通过对两个亚波长尺寸的介电球体成像观察到散射效应，每个球体直径为480μm，折射率分别为2和6，在0.3THz左右，检测到了折射率为2的颗粒的磁偶极子模式。实验结果证实，即使使用低折射率材料，球体的图像对比度也主要受米氏共振频率附近的散射效应影响。这项工作代表了太赫兹区域内亚波长尺寸结构检测和表征方面的重大进展。此外，这些发现不仅限于太赫兹频率范围，在光学、红外和毫米波范围内的传感、成像和尺寸测量等领域具有潜在应用。
