@ARTICLE\{IMM2001-0161,
    author       = "J. F. Corney and O. Bang",
    title        = "Modulational Instability in Periodic Quadratic Nonlinear Materials",
    year         = "2001",
    month        = "sep",
    pages        = "1-4/133901",
    journal      = "Physical Review Letters",
    volume       = "87",
    editor       = "",
    number       = "13",
    publisher    = "",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/161-full.html",
    abstract     = "We investigate the modulational instability of plane waves in quadratic nonlinear materials with linear and nonlinear quasi-phase-matching gratings. Exact Floquet calculations, confirmed by numerical simulations, show that the periodicity can drastically alter the gain spectrum but never completely removes the instability. The low-frequency part of the gain spectrum is accurately predicted by an averaged theory and disappears for certain gratings. The high-frequency part is related to the inherent gain of the homogeneous non-phase-matched
material and is a consistent spectral feature."
}