Cavity phenomenon and terahertz radiation of a tall stack of intrinsic Josephson junctions wrapped by a dielectric material

In order to enhance the radiation power in the terahertz band based on intrinsic Josephson junctions of Bi₂Sr2CaCu₂O8+δ single crystal, we investigate a long cylindrical sample embedded in a dielectric material. Tuning the dielectric constant, the radiation power has a maximum which is achieved when it equals the dissipation caused by the Josephson plasma. This yields the optimal dielectric constant of the wrapping material in terms of the properties of a BSCCO single crystal. The maximal radiation power is found proportional to the product of the critical superconducting current squared and the typical normal resistance, which offers a guideline for choosing superconductors as a source of strong radiation.