Detailed investigation of two-dimensional Josephson junction array circuits

Spatially resolved detection of mutually locked Josephson junctions in arrays

“…15 and 16. By measuring the current versus voltage (IϪV) curve of the detector junction we are able to detect coherent oscillating states in some arrays by the appearance of Shapiro steps. 15 However, this coherent state is not tuneable over a broad range of frequencies. The tunability may be limited due to internal and external resonances.…”

“…From the detector IϪV curve we estimate a detected microwave power of approximately 35 nW. In consideration of reflection losses during the transmission of the microwave power from the array to the detector 15 and of the nonmatched load ͑detector͒ impedance, this amount of detected power indicates a high degree of coherence in the array.…”

“…The 1 spread in the shunt resistors is about 15%, becoming important as one is interested in high frequencies. 15 In order to measure the output power of the array, a detector junction is coupled to the array via a microstripline in a similar way as has been done by Benz and Burroughs. 6 Figure 1 shows a cross-sectional view of an array with a microwave coupling circuit and a detector junction.…”

“…Phase locking in arrays of Josephson junctions is of broad theoretical 1-5 and experimental [6][7][8][9][10][11][12][13][14][15] interest. From the application point of view the array state where all the junctions oscillate in-phase is the most desired one, because this in-phase state guarantees maximum microwave output power together with minimum linewidth.…”

“…One can measure the power of the emitted microwave radiation, which depends on the number of phase-locked junctions. 6,8,13,15 Another way is to measure the linewidth of the emitted radiation, which decreases as the number of phase-locked junctions increases. 7,9 However, both methods are associated with restrictions.…”