Emission of terahertz electromagnetic waves driven by an external current in intrinsic Josephson junctions

We propose a mechanism for the strong emission of terahertz wave recently observed in current-biased mesa-shaped Bi2Sr2CaCu2O8 single crystals by Ozyuzer et al. When the mesa length is approximately equal to the c-axis penetration depth and an external current is applied along the c-axis of the mesa-crystal, the Josephson oscillation can cause the resonance excitation of cavity-mode of the transverse Josephson plasma in the voltage state. When the oscillating electric and magnetic fields excited inside the mesa have antinodes at the surfaces, the electromagnetic wave with Josephson frequency is strongly emitted into the vacuum. We evaluate the frequency and power of emitted electromagnetic wave to be respectively of the orders of THz and 103 W/cm3 near the retrapping region