固有ジョセフソン接合を用いたテラヘルツ波発振素子のキャビティモードの計算

概要

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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.