准光技术改善Josephson结与毫米波的耦合

IMPROVEMENT IN THE COUPLING OF JOSEPHSON JUNCTION AND MM WAVE RADIATION BY USING QUASIOPTICS SCHEME

在高温超导Ｊｏｓｅｐｈｓｏｎ结混频器的研究中，要获得较好的性能指标，结与毫米波源的耦合能力是很重要的参数．研究如何提高这种耦合能力，在实际应用中有着十分重要的意义．为此，我们用准光学原理，设计了ＬＡＯ介质透镜系统，以ＹＢＣＯ台阶结为检测元，分别测量了在增加了该系统前后，相同的毫米波功率对Ｊｏｓｅｐｈｏｓｎ结零台阶电流的压缩情况．实验结果表明，在增加了该光学系统后，结与毫米波的耦合能力有了约１４ｄＢ的显著提高．该系统可用于毫米波和亚毫米波段的谐波混频器上．

The coupling between Josephson junction and external mm wave radiation is important to a HTS Josephson mixer. It is meaningful to study how to improve this coupling. In this paper, we design a LAO QuasiOptics scheme to increase it. In our experiment, we used a LAO Josephson step junction as the inspector and measured the IV curves of this junction with and without the LAO QuasiOptics scheme when the 100GHz external millimeter radiation was present. The different height of the zeroth Shapiro step shows that the coupling increases greatly if the LAO QuasiOptics scheme is used. We also calculated the aperture efficiency of our system at 100GHz. This technqiue can be used in harmonic mixer at mm and submm wavebands.