Testing of Josephson Array Antennas and Trim Current Tuning

摘要

This report results from a contract tasking University of Erlangen- Nuremberg as follows: contractor will investigate novel designs of triangular Josephson Junction arrays attempting to improve the high-frequency performance of the arrays in two ways; first, increase the operation frequencies and second, increase the output power of the millimeter-band radiation to level enabling practical application of the arrays. Three approaches will be investigated. First, trimming of currents at the array edges is expected to stabilize coherent oscillations and increase the operation margins (output power). Second, it appears promising to set up a traveling wave in a transmission line that contains an array comparable with the wavelength. Third, testing dipole-like active antennas to couple radiation out from arrays is a high priority task for emission in free space at high frequencies. The contractor will experimentally verify the above concepts by designing new circuits and performing experiments with Nb/AOx/Nb Josephson Junction arrays. For these experiments, the contractor will use a millimeter-wave band receiver as well an on-chip detection circuits up to 300 GHz. Spatially-resolved measurements using low temperature scanning laser microscopy will be performed in order to monitor array dynamics at the junction level. Furthermore, the contractor intends to design a dipole antenna and test it with an integrated receiver in 400-500 GHz frequency range. For this purpose, improvements for a flux-flow oscillator as a local oscillator may be needed. Finally, the contractor will perform experiments with shunted junction arrays in order to simulate intrinsically overdamped high-Tc junctions and explore a possibility of using high Tc layered junctions for oscillator application.