Research on tunable wavelength optical vortex source in high-power terahertz coherent transition radiation

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K12539
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 80040:Quantum beam science-related
• Research Institution: Nihon University
• Principal Investigator: SAKAI Takeshi 日本大学, 理工学部, 准教授 (20409147)
• Co-Investigator(Kenkyū-buntansha): 清 紀弘 国立研究開発法人産業技術総合研究所, 計量標準総合センター, 上級主任研究員 (20357312)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: テラヘルツ波 / 光渦 / コヒーレント遷移放射 / 電子線形加速器

Outline of Final Research Achievements

This study aims to generate tunable THz-band vortex beam using a 100 MeV electron linac at the LEBRA, Nihon University. The THz coherent transition radiation vortex beam source was manufactured using aluminum with a helical target with a topological charge of 1. The topological charge represents the number of phase rotations within the cross-section around a singularity. A versatile mechanical shutter blade was modified with titanium to achieve the tunability of the helical structure. The aluminum helical target was inserted into the beamline to induce transition radiation, which was then extracted and measured in the atmosphere. Although influenced of absorption by atmospheric water vapor, the spectrum, two-dimensional distribution, power intensity, and polarization state were successfully measured using a wire grid, demonstrating the generation of the THz coherent transition radiation vortex beam.

Free Research Field

加速器科学

Academic Significance and Societal Importance of the Research Achievements

これまでに国内外で実施されている高強度短パルスレーザーやアンジュレーター、ジャイラトロン等を用いるようなテラヘルツ帯域の光渦生成とは違い、金属ターゲットを用いたテラヘルツ帯の遷移放射光渦生成が大学レベルの小型加速器を用いて可能になったことから、今後さらなる詳細測定、性質解明、利用実験など幅広く進めていくことで、応用研究も波及していくと思われる。