Tunable detection of radiation from HTSC Josephson junction arrays

We have investigated the mutual phase interaction between a single detector junction and a phase-locked three-junction array of high-T-c Josephson junctions. The YBCO Josephson junctions were fabricated on a MgO bicrystal substrate. We measured the radiation power of a Josephson-junction array using an off-chip coupled to a radiometer and on-chip coupled to a single junction from centimeter- to millimeter-wave ranges. The Josephson oscillation power excited the resonant mode coupled to the coplanar microstrip loops. Clear self-induced Shapiro steps were observed in the current-voltage curves of the detector junction. The power transfer to the single detector junction was estimated from the modulation of the Shapiro step height. The maximum detected power level was about 7 nW at frequency 150-250 GHz. (C) 1999 Elsevier Science B.V. All rights reserved.