Microwave coupling of the Josephson junction arrays with an external source

Abstract

We have fabricated a YBa2Cu30,(YBCO) array of five Josephson junctions designed with additional inductive coupling lines(A1CLs). The junctions in this array were dcbiased in parallel to oscillate coherently in-phase and integrated with AICLs to improve the impedance matching between this array and external circuits such as a waveguide. The effect of AICLs was investigated by studying its influence on the currentvoltage characteristics of the Josephson junction array(JJA) under external microwave irradiations with frequency of 22 GHz. The experimental results show that the behavior of the Shapiro-steps depends upon the effective inductance of AICLs which affects the total impedance and microwave coupling. We were able to obtain an oscillation frequency of about 73 % of the maximum available frequency calculated from the characteristic voltage of the Josephson junctions in the array at a temperature of 12 K. By calculating the total impedance of the array, we obtained the suitable parameters of the array for microwave coupling with waveguide for various values of inductance, ac frequencies and number of Josephson junctions.

Detected power and linewidth of Josephson self-radiation from frequency-locked and microwave-coupled arrays in a waveguide detection system

“…In the external detection system shown in figure 2 and for an impedance of the Josephson junction (Z J ) that is much smaller than that of the detection system (Z 0 ), the self-radiation power (P rN ) and total impedance (Z J N ) of our frequency-locked and microwave-coupled array [7] of N Josephson junctions and serial array of N identical Josephson junctions are N times larger than those of a single Josephson junction [8,10]. Also, for the same values of I c and R N of Josephson junctions in the arrays, the detected power (P dN ) is N 2 times larger than that of a single junction for coupling coefficients and self-radiation powers that are N times higher.…”

“…Thus the detected power of Josephson selfradiation from the JJA can be enhanced by the effects of frequency locking and microwave coupling. In our previous report [7,8], the microwave coupling of the array with an external waveguide detection system is strongly affected by n(≡ L/L 0 ). Here, L and L 0 are the inductance of AICLs and superconducting microstrip lines placed at both sides of Josephson junctions, respectively.…”

“…Here, L and L 0 are the inductance of AICLs and superconducting microstrip lines placed at both sides of Josephson junctions, respectively. In this paper, n is fixed to 100, for which Z tot has a similar value to that when n is infinite [8].…”