Using Josephson vortex lattices to generate, detect and control THz radiation

We propose several devices to generate, filter, and detect THz radiation using strongly anisotropic layered superconductors, such as Bi2Sr2CaCu2O8+δ. (1) We show that a moving Josephson vortex (JV) in spatially modulated layered superconductors generates out-of-plane THz radiation. Remarkably, both the magnetic and in-plane electric fields radiated are of the same order, which is very unusual for any good-conducting medium. Therefore, the out-of-plane radiation can be emitted to the vacuum without the standard impedance mismatch problem. (2) We show that JV lattices can produce a photonic band gap structure (THz photonic crystal) with easily tuneable forbidden-frequency zones controlled by the in-plane magnetic field. The scattering of electromagnetic waves by JVs results in a strong magnetic-field dependence of the reflection and transparency. These proposals are potentially useful for controllable THz filters. (3) We predict the existence of surface waves in layered superconductors in the THz frequency range, below the Josephson plasma frequency ωJ. These predicted surface Josephson plasma waves can be resonantly excited by incident THz waves, producing a huge enhancement of the wave absorption. This effect could be used for new THz detectors.