Construction of mapping systems of superconducting properties under magnetic fields

本研究的目的是开发基于飞秒激光激发太赫兹辐射现象的超电流可视化系统，这是我们在1995年发现的。通过聚焦直径为20微米的激光光斑，并在检测太赫兹辐射振幅的情况下对样品进行扫描，我们成功地实现了高Tg超导薄膜中二维超导流的可视化。此外，我们通过映射太赫兹辐射的两个相互正交的极化分量，成功地可视化了通量捕获状态下的矢量超导流。用Bean模型半定量地解释了系统测量的超电流行为。研究了聚焦太赫兹辐射成像系统，并将其应用于光激发载流子分布的可视化。这些太赫兹辐射的新应用将促进太赫兹技术的发展。

The purpose of this study is to develop systems for visualizing supercurrent based on a femtosecond-laser excited terahertz radiation phenomenon, which we found in 1995. By focusing a laser spot to 20 micrometer in diameter and scanning the spot on a sample with detecting the THz radiation amplitude, we succeeded in visualizing two-dimensional supercurrent flow in high Tg superconducting films. Further, we succeeded in visualizing vector supercurrent flow under the flux trapped state by mapping two mutually orthogonal polarization components of THz radiation. The behavior of the supercurrent measured by this system is explained by the Bean model semi-quantitatively. The imaging system using the focused THz radiation is also developed and applied to visualize the photoexcited carrier distribution in semiconductors. These new applications of THz radiation will contribute to the growing THz technology.