Abstract
To evaluate cavity resonance modes in terahertz-wave oscillators using intrinsic Josephson junction stacks in high-temperature superconductors, an analytical solution of the coupled sine-Gordon equation was obtained by a continuous approximation. For a rectangular stack with a realistic scale, 80μm wide, 300μ m long and 1.1μm (∼700 junctions in the stack) in height, I-V characteristics and field distributions were calculated from the solution. Peak structures were appeared in the I-V curves and corresponded to cavity resonance modes, which were similar to those in a rectangular waveguide cavity. The maximum peak height was obtained at a bias voltage where the TEy111 mode at 0.51 terahertz was excited by the ac Josephson effect. The peak height decreased with increasing a radiation conductance that was introduced for including a radiation loss in the calculation. For design of antenna-coupled oscillators, a junction impedance was also evaluated. These results are useful for future improvement of the oscillators using intrinsic junctions.
