Cavity mode identification for coherent terahertz emission from high-Tc superconductors.

Stacks of intrinsic Josephson junctions in BiSrCaCuO emit intense and coherent terahertz waves determined by the internal electromagnetic cavity resonance. We identify the excited transverse magnetic mode by observing the broadly tunable emissions from a nearly square stack and simulating the scattering spectrum. We employ a wedge-type interferometer to measure spatially-integrated power independently of the far-field pattern. The simulation results are in good agreement with observed resonance behaviors as a function of frequency.