Generation of coherent electromagnetic radiation by layered superconducting compounds

Sources of coherent radiation can be developed on the basis of layered superconducting compounds. These sources are tunable over a broad frequency range. Their energy characteristics are close to those of semiconductor lasers. A model of single crystals of layered high T_c superconductors is discussed. It is assumed that the layers are coupled with each other by a Josephson tunneling of electrons. As electromagnetic radiation is generated by the current of electron pairs, the electron tunneling occurs under the conditions of the time-varying Josephson effect, under the influence of two voltages: a static voltage applied to the superconducting layers and an alternating voltage induced by the field excited in the system.