Abstruct-In submillimeter wave region, we junctions. Because of the high gap voltage of epitaxial have studied the modulation of self-resonant NbCN/MgO/NbCN junctions [6], the frequency shift due to modes in NbCN/MgO/NbCN Josephson junctions quasiparticle injection and Q factor of junctions under the (detectors). The tuning mechanism is based on the quasiparticle injection via an overlaid tunnel junction (injector). From the current-voltage of resonant frequencies Af and Q factors due to electrode loss at the injqcted state Qrnj have been In this section, we describe briefly the theory of selfestimated to be Af/f(O)=O.ll and Qinj=lOO at resonsnce. Samples used for this work are stacked double 470GHz, where f(0) is the resonant frequency tunnel junctions shown in Fig. 1. The lower junction, Called without quasiparticle injection. It is found Qinj aS an injector, creates the nonequlibrium S t a t e in the middle decreases with increase of the injector bias NbCN film, while upper one, called as a detector, probes the voltage. shifts of resonant frequencies due to the quasiparticle injection. With an applied magnetic field Be, current steps (Fiske steps) are observed on current-voltage (I-V) characteristics of detector. It is due to self-resonant modes in the detector, in which oscillation frequencies based on a.c.Josephson effect vdet/@o are equal to resonant frequencies of detector given by injection were successfully measured below 70GHz.
characteristics of detectors, the maximum shift
THEORY OF RESONANCE