New strategies for the mutual synchronization of very large Josephson junction networks

该项目的目的是研究超大型约瑟夫森结网络相互同步的新策略，目的是显著提高基于相位同步约瑟夫森结(JJ)的亚毫米波长辐射源。信号源将由大型1D或2D JJ阵列组成，在输出功率方面，应至少比目前最先进的几个10微瓦的值高一个数量级。信号源应在很宽的发射频率范围内可调。我们将主要研究基于三种不同类型的JJ的数组。第一种是以NbSi为势垒层的SnS约瑟夫森结(“S”=超导体，“N”=正常金属)。通过这些阵列，我们将确定适当的几何配置和同步方案，并开发合适的高频设计，例如基于行波天线。我们打算学习如何用一组简单的振荡模式来设计约瑟夫森系统，从而有效地与JJ相互作用，以及如何通过使用条形电动力学元件来增加寄生模式的损耗来抑制寄生模式。第二种类型的JJ是外部分流的SIS(“I”=绝缘体)隧道结，它使用AlOx或AlN作为阻挡层。基于这些JJ的阵列还允许集成谐波混频器和片上检测方案等元件。第三种类型的阵列使用聚焦氦离子束图案化产生的YBa2Cu3O7结。对于这一行的研究，制造和同步机制都比其他研究更不成熟，但使用这种阵列可能的好处是，至少在原则上可以实现更高的发射频率，超过1太赫兹。对于所有阵列，我们将陆续改进和优化优值系数(输出功率、最大频率、辐射线宽)。目标频率将在0.2至1太赫兹之间，最大输出功率将在几个100微瓦的范围内，线宽将在几个MHz或更小的范围内。拟议的项目汇集了一个德国团体和三个俄罗斯团体，他们都在各自的领域拥有国际声誉，并在国际合作方面有经验。每个小组在与项目目标相关的领域都有公认的记录，参与小组之间以前的合作也非常成功。

The aim of the project is to investigate new strategies for the mutual synchronization of very large Josephson junction networks with the objective to significantly advance sub-mm wavelength radiation sources based on phase-synchronized Josephson junctions (JJs). The sources will consist of large 1D or 2D JJ arrays and, in terms of output power, shall exceed the present state-of-the-art values of several 10 µW by at least an order of magnitude. The sources shall be tunable over a wide range of emission frequencies. We will study arrays based on mainly three different types of JJs. The first type are SNS Josephson junctions (with "S" = superconductor, "N" = normal metal) using NbSi as the barrier layer. With these arrays we will identify proper geometric configurations and synchronization schemes and develop suitable high-frequency designs, e.g. based on travelling wave antennas. We intend to learn how to design Josephson systems with a simple set of oscillation modes that effectively interact with the JJs, as well as suppress parasitic modes by increasing their losses due to the use of strip electrodynamic elements. The second type of JJs are externally shunted SIS ("I" = Insulator) tunnel junctions, which use AlOx or AlN as barrier layers. Arrays based on these JJs additionally allow integration of elements such as harmonic mixers and on-chip detection schemes. The third type of arrays uses YBa2Cu3O7 junctions created by focused helium ion beam patterning. For this line of research both fabrication and the mechanisms of synchronization are less established than for the other ones but the possible gain of using such arrays is that much higher emission frequencies, exceeding 1 THz, are feasible at least in principle. For all arrays we will successively improve and optimize the figure of merits (output power, maximum frequency, linewidth of radiation. Target frequencies will be in the range between 0.2 and 1 THz, maximum output powers in the range of several 100 µW and linewidths in the range of a few MHz or less. The proposed project brings together one German and three Russian groups who all have an international reputation in their field and who have experience in international collaborations. Each group has a recognized track record in a field relevant for project goals, and prior collaborations between the participating groups have been highly successful.