0.14THz过模表面波振荡器的模式分析

采用理论分析和实验验证相结合的方法, 研究了0.14 THz过模表面波振荡器(过模比D/λ≈3)中太赫兹波模式成分的分布. 首先针对具有圆周对称结构的过模切连科夫器件, 建立了用于模式分析的纵向场分解法. 接着基于2.5维PIC(Particle-in-cell)软件的电场模拟结果, 采用该方法对0.14 THz表面波振荡器的模式进行了详尽的理论分析. 结果表明, 器件中不同结构区域的太赫兹波模式成分不同, 相互间存在模式转换, 输出模式以TM₀₂和TM₀₃模为主, 并伴有少量TM₀₄模. 最后利用图像显示法获取了0.14 THz表面波振荡器的近场辐射能量分布, 与由模式分析结果得到的理论分布符合的较好, 证明了纵向场分解法用于模式分析的可行性和结果的正确性.关键词：过模表面波振荡器模式分析场分解法

Mode analysis of 0.14 THz overmoded surface wave oscillator

Mode analysis of the terahertz wave generated by 0.14 THz overmoded surface wave oscillator (SWO) (overmoded ratio D/λ≈ 3) is theoretically accomplished and experimentally validated. At first, longitudinal field-expansion method for mode analysis is established aiming at overmoded Cherenkov devices. Then this method is used to analyze the theoretical mode content of 0.14 THz SWO in detail based on the simulation results of electric field extracted from a 2.5-dimensional PIC (particle-in-cell) code. Results show that the mode content of terahertz wave in different characteristic regions of the oscillator is varied due to the mode conversion, and it is dominated by TM₀₂ and TM₀₃ modes accompanied by a small quantity of TM₀₄ mode at the output. Finally, the energy distribution in the near-field radiation of 0.14 THz SWO is obtained by image-displaying method. The experimental result is reasonably in accord with the theoretical distribution calculated from the mode analysis results under experimental conditions, testifying the feasibility of longitudinal field-expansion method for the mode analysis and the correctness of its results.
Keywords：overmodedsurface wave oscillatormode analysisfield-expansion method