Letter abstract
Nature Physics 2, 521 - 525 (2006)
doi:10.1038/nphys358
Subject Categories: Condensed-matter physics | Optical physics | Materials physics
Analogues of nonlinear optics using terahertz Josephson plasma waves in layered superconductors
Sergey Savel'ev1,2, A. L. Rakhmanov1,3, V. A. Yampol'skii1,4 and Franco Nori1,5
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 J (refs 1, 2), which being in the terahertz (THz) range, is important for applications3. This feature is fuelling a growing interest in studies of JPWs (see, for example, refs 4–7). However, nonlinear (NL) JPWs have not yet been studied. It is a challenge to understand nonlinearities around the plasma frequency, where the interplay between the unusual spectrum and the nonlinearity of the JPWs is most pronounced. Here, we predict the propagation of NL JPWs with frequencies below J, which is unusual for plasma-like excitations. In analogy to NL optics, these waves exhibit numerous remarkable features, including the slowing down of light (when the group velocity 
/k
0), self-focusing effects and the pumping of weaker waves by stronger ones. The nonlinearity for >J can potentially be used for transforming continuous THz radiation into amplified pulses.
- Frontier Research System, The Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-0198, Japan
- Department of Physics, Loughborough University, Loughborough LE11 3TU, UK
- Institute for Theoretical and Applied Electrodynamics Russian Academy of Sciences, 125412 Moscow, Russia
- A. Ya. Usikov Institute for Radiophysics and Electronics Ukrainian Academy of Sciences, 61085 Kharkov, Ukraine
- Center for Theoretical Physics, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040, USA
Correspondence to: Franco Nori1,5 e-mail: nori@umich.edu
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