Out-coupling characteristics of partial resonator mirror for compact terahertz free-electron laser

IF 0.8 4区 物理与天体物理 Q3 PHYSICS, MULTIDISCIPLINARY
Varun Pathania, Hyeon Sang Bark, Kyu-Ha Jang, Kitae Lee, Young Uk Jeong
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Abstract

Terahertz light sources with small size and high output enable a variety of new applications. Free-electron laser (FEL) is the most powerful light source in the terahertz (THz) range with perfect wavelength tunability. However, the size of the FEL facility is too large. We are developing a table-top THz FEL using a small microtron accelerator. Through the development of a high-performance and compact undulator and a new waveguide-mode resonator, we confirmed that an FEL size of 1.5 × 2 m2 is possible. One of the reasons we could design the small FEL is because we do not use electromagnets to force the electron beam into and out of the FEL resonator. We have developed an out-coupling mirror of the FEL resonator for a wide spectral range from 0.5 to 1 THz to have a structure in which the electron and THz beam transmit simultaneously without any bending magnets. The out-coupling mirror has wire-grid-polarizer (WGP) structure in the center. This paper discusses optimizing the WGP's parameters like wire thickness and period to get appropriate reflectance and transmittance in the 0.5–1 THz region and has low electron beam loss in the waveguide-based resonator using the COMSOL Multiphysics simulation. Simulations found the optimized value of wire thickness and period as 20 and 100 µm, respectively. We further calculated the TE transmittance of the WGP, which is 1-030% for the optimized values, depending on the frequency, ranging from 0.5 to 1 THz. Experiments using the THz time-domain spectroscopy method validated that the measured results agreed with those of the simulations.

Abstract Image

用于紧凑型太赫兹自由电子激光器的部分谐振器镜面的外耦合特性
太赫兹光源具有体积小、输出高的特点,可用于各种新的应用领域。自由电子激光器(FEL)是太赫兹(THz)范围内最强大的光源,具有完美的波长可调谐性。然而,自由电子激光设备的体积过于庞大。我们正在利用小型微加速器开发台式太赫兹 FEL。通过开发高性能的紧凑型减压器和新型波导模式谐振器,我们证实 1.5 × 2 m2 的 FEL 尺寸是可行的。我们之所以能设计出这么小的 FEL,其中一个原因是我们不使用电磁铁来迫使电子束进出 FEL 谐振器。我们已开发出一种适用于 0.5 至 1 太赫兹宽光谱范围的 FEL 谐振器外耦合镜,这种结构无需任何弯曲磁铁即可同时传输电子束和太赫兹光束。外耦合镜的中心具有线栅偏振器(WGP)结构。本文利用 COMSOL Multiphysics 仿真技术讨论了如何优化 WGP 的参数,如导线厚度和周期,以便在 0.5-1 THz 区域获得适当的反射率和透射率,并降低波导谐振器中的电子束损耗。仿真结果表明,导线厚度和周期的优化值分别为 20 微米和 100 微米。我们进一步计算了 WGP 的 TE 透射率,根据频率的不同,优化值为 1-030%,范围为 0.5 至 1 太赫兹。使用太赫兹时域光谱法进行的实验验证了测量结果与模拟结果一致。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of the Korean Physical Society
Journal of the Korean Physical Society PHYSICS, MULTIDISCIPLINARY-
CiteScore
1.20
自引率
16.70%
发文量
276
审稿时长
5.5 months
期刊介绍: The Journal of the Korean Physical Society (JKPS) covers all fields of physics spanning from statistical physics and condensed matter physics to particle physics. The manuscript to be published in JKPS is required to hold the originality, significance, and recent completeness. The journal is composed of Full paper, Letters, and Brief sections. In addition, featured articles with outstanding results are selected by the Editorial board and introduced in the online version. For emphasis on aspect of international journal, several world-distinguished researchers join the Editorial board. High quality of papers may be express-published when it is recommended or requested.
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