Department of Physics, KAIST, Daejeon, South Korea.
Opt Lett. 2013 Jan 15;38(2):166-8. doi: 10.1364/OL.38.000166.
Terahertz time-domain spectroscopy probes anomalous phase-shift caused by wave diffraction from a subwavelength-scale metal slit or aperture. Carrier frequency phase measurements in the far-field region reveals that nearly 30° phase advance is induced from a subwavelength slit diffraction and that 180° phase-advance from a subwavelength aperture. These results indicate that the conventional 90° phase advance of diffracted waves in the far-field region, known as the Gouy phase shift, is not valid for subwavelength diffraction phenomena. The physical origin of these phase-shift anomalies is attributed to induced electric currents or magnetic dipole radiation, and theoretical analyses based on these factors are in good agreement with the experimental results.
太赫兹时域光谱探测到由亚波长尺度金属狭缝或孔径的波衍射引起的异常相移。在远场区域进行载波频率相位测量表明，亚波长狭缝衍射会导致近 30°的相位超前，而亚波长孔径则会导致 180°的相位超前。这些结果表明，远场区域中衍射波的常规 90°相位超前，即古依相位移动，对于亚波长衍射现象并不适用。这些相位移动异常的物理起源归因于感应电流或磁偶极辐射，基于这些因素的理论分析与实验结果吻合良好。
