School of Electronics Engineering and Computer Science, Peking University, Beijing, 100871, P. R. China.
Sci Rep. 2017 Aug 4;7(1):7265. doi: 10.1038/s41598-017-07545-6.
Terahertz applications urgently require high performance and room temperature terahertz sources. The gyrotron based on the principle of electron cyclotron maser is able to generate watt-to-megawatt level terahertz radiation, and becomes an exceptional role in the frontiers of energy, security and biomedicine. However, in normal conditions, a terahertz gyrotron could generate terahertz radiation with high efficiency on a single frequency or with low efficiency in a relatively narrow tuning band. Here a frequency tuning scheme for the terahertz gyrotron utilizing sequentially switching among several whispering-gallery modes is proposed to reach high performance with broadband, coherence and high power simultaneously. Such mode-switching gyrotron has the potential of generating broadband radiation with 100-GHz-level bandwidth. Even wider bandwidth is limited by the frequency-dependent effective electrical length of the cavity. Preliminary investigation applies a pre-bunched circuit to the single-mode wide-band tuning. Then, more broadband sweeping is produced by mode switching in great-range magnetic tuning. The effect of mode competition, as well as critical engineering techniques on frequency tuning is discussed to confirm the feasibility for the case close to reality. This multi-mode-switching scheme could make gyrotron a promising device towards bridging the so-called terahertz gap.
太赫兹应用迫切需要高性能和室温太赫兹源。基于电子回旋脉塞原理的回旋管能够产生瓦级到兆瓦级的太赫兹辐射，在能源、安全和生物医学等前沿领域发挥着特殊作用。然而，在正常情况下，太赫兹回旋管可以在单个频率上以高效率产生太赫兹辐射，或者在相对较窄的调谐带宽内以低效率产生太赫兹辐射。本文提出了一种利用多个回音壁模式顺序切换的太赫兹回旋管频率调谐方案，以同时实现宽带、相干和高功率的高性能。这种模式切换回旋管有望产生具有 100GHz 级带宽的宽带辐射。更宽的带宽受到腔的频率相关有效电长度的限制。初步研究将预群聚电路应用于单模宽带调谐。然后，通过大范围磁场调谐中的模式切换产生更多的宽带扫描。讨论了模式竞争的影响以及对频率调谐的关键工程技术，以确认接近实际情况的案例的可行性。这种多模式切换方案可以使回旋管成为一种有前途的器件，以弥合所谓的太赫兹间隙。
