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Josephson plasma waves in layered superconductorsDepartment of Physics, Loughborough University Friday, 10 Nov 2006, W2.19 Electromagnetic waves in layered superconductors are known as Josephson plasma waves (JPWs). An important property of JPWs is the gap in their energy spectrum: JPWs can propagate if the frequency is above the Josephson plasma frequency, which being in the terahertz (THz) range, is important for applications. This feature is fuelling a growing interest in studies of JPWs.We show [1] 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.We show [2] 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.We predict [3] the existence of surface waves in layered superconductors in the THz frequency range, below the Josephson plasma frequency. These predicted surface Josephson plasma waves can be resonantly excited by incident THz waves, producing an enhancement of the wave absorption. This effect could be used for new THz detectors.We predict [4] the propagation of NL JPWs with frequencies below the Josephson plasma frequency, which is unusual for plasma-like excitations. In analogy to NL optics, these waves exhibit numerous remarkable features, including the slowing down of light, self-focusing effects and the pumping of weaker waves by stronger ones. 1. S. Savel’ev, V. Yampol’skii, A. Rakhmanov, and F. Nori, Phys. Rev. B 72, 144515 (2005) |
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