Numerical Study of Radiation Pattern from Intrinsic Josephson Junctions Attached to Finite Size Substrates

In this study, we have investigated numerically three dimensional radiation patterns from mesa-structured intrinsic Josephson junctions (IJJs) attached to finite size substrates. We have calculated electromagnetic fields inside and outside of IJJs simultaneously using three dimensional calculation model. The radiation patterns emitted by the mesa have been calculated for three different substrates. We have found that the radiation patterns reflect the existence of dual radiation source, that is, uniform part of ac Josephson current and non-uniform part of ac Josephson current corresponding to the cavity modes. Moreover, we have found that the radiation pattern changes dramatically with the width of the substrates. The radiation patterns are strongly affected by the diffraction at substrate edges.