HTS Josephson junctions arrays for high-frequency mixing

International audience; We designed, fabricated and measured short one-dimensional arrays of masked ion-irradiated YBa 2 Cu 3 O 7 Josephson junctions embedded into log-periodic spiral antennas. They consist of 4 or 8 junctions separated either by 960 nm or 80 nm long areas of pristine material. Large spacing arrays show " Giant " Shapiro steps in the hundreds-GHz band at 66 K and are tested as Josephson mixers with improved impedance matching. On the contrary, small spacing arrays behave as one junction with a lower superconducting transition temperature, hence forming a single weak link on distances up to 880 nm. Such design opens a new way to increase the I c R n product of the devices, and therefore the efficiency of the Josephson mixers. Hints on the origin of the observed long range proximity effect are proposed.