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

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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.