電磁波の動的可視化による次世代ミリ波・テラヘルツ波デバイスの研究

在这一年里，我在学习中取得了三个重要的成就。1)首先，通过演示商用30 GHz至500 GHz宽带宽球波产生装置的特性，阐明了电光（EO）测量表征太赫兹（THz）器件的能力或“价值”。这是第一个通过使用EO探头在自由空间中可视化太赫兹器件的振幅和相位分布来表征高达500 GHz的太赫兹器件。利用有机EO材料（4-二甲氨基- n -甲基-4-甲酰基苯乙烯唑，DAST）提高灵敏度和引入折射率接近空气的聚苯乙烯泡沫支架降低侵入性是获得该结果的两个关键技术。2)其次，进一步研究了“太赫兹区光子纳米射流”（Terajet）的特性。特别地，阐明了由中尺度介质立方体产生的Terajet的角特性。实验结果表明，产生的Terajet与入射光束完全相同，并且在较宽的照明角度内保持了Terajet的半最大亚波长全宽度。第三，提出并论证了Terajet的两种实际应用。一是提高太赫兹成像系统的空间分辨率。二是提高EO探头的灵敏度。

In this year, three important achievements were obtained in my study.1) First, the capability or “value” of electro-optic (EO) measurement to characterize terahertz (THz) devices was clarified by demonstrating the characterization of a commercially available broad bandwidth spherical-wave-generating device from 30 GHz to 500 GHz. It was the first THz device characterization up to 500 GHz by visualizing the amplitude and phase distributions in free-space from the device using the EO probe. The sensitivity enhancement by exploiting an organic EO material (4-dimethylamino-N-metyl-4-stilbazolium tosylate, DAST) and the invasiveness reduction by introducing a Styrofoam holder, which has refractive index close to air, were two key techniques to obtain this result.2) Second, the characteristics of the “Terajet”, which is defined as the photonic nanojet in the THz region, were studied further. Particularly, the angular characteristics of the Terajet generated from a mesoscale dielectric cube were clarified. The experimental results indicated that the generated Terajet is identical to the incident beam and the subwavelength full width at half maximum of the Terajet is maintained within a wide angle of illumination.3) Third, two practical applications of the Terajet were proposed and demonstrated. One is to enhance the spatial resolution of THz imaging system. The other is to enhance the sensitivity of the EO probe.