高功率毫米波圆波导半径微扰模式变换器的优化设计

从半径渐变波导的耦合波方程出发，利用龙格-库塔法进行优化数值迭代，得到在3 mm波段，TE03-TE02, TE02-TE01高效率模式变换器的设计参数。通过优化程序，设计出了6周期TE03-TE02和3周期TE02-TE01模式变换器优化尺寸。利用CST微波工作室电磁仿真软件对结构尺寸进行优化仿真，仿真结果与优化程序计算结果基本一致。以此数据设计中心频率94 GHz的TE03-TE02，TE02-TE01模式变换器功率转换效率可以达到98.5%以上，90%功率转换的绝对带宽分别达到3.5和7.0 GHz以上，优于设计要求。

Bessel-Gauss resonator based on an axicon with a plane output mirror

A simple concept is applied to the construction of a Bessel-Gauss resonator based on an axicon witha plane output mirror. Fox-Li algorithm and numerical integral are applied respectively to describe the radical amplitude at output mirror and the three-dimensional field distribution of output beam. Analysis reveals that the dominant mode of the resonator has similar features as zero-order Bessel-Gauss beams do. Effect of varying the cavity length on the output transverse profile of the dominant mode of the cavity is discussed. Simulation results show that the features of the dominant mode of the resonator remain unchanged when the cavity length change is small. The resonator scheme based on Nd, YAG laser was implemented in an experiment to confirm the possibility of generating zero-order Bessel-Gauss beams. The output transverse intensity distributions captured by beam analyzer roughly agree with the theoretical expectations.