Phenomenon whereby deviations from a periodic waveform are reinforced by nonlinearity
In the fields of nonlinear optics and fluid dynamics, modulational instability or sideband instability is a phenomenon whereby deviations from a periodic waveform are reinforced by nonlinearity, leading to the generation of spectral-sidebands and the eventual breakup of the waveform into a train of pulses.[1][2][3]
It is widely believed that the phenomenon was first discovered − and modeled − for periodic surface gravity waves (Stokes waves) on deep water by T. Brooke Benjamin and Jim E. Feir, in 1967.[4] Therefore, it is also known as the Benjamin−Feir instability. However, spatial modulation instability of high-power lasers in organic solvents was observed by Russian scientists N. F. Piliptetskii and A. R. Rustamov in 1965,[5] and the mathematical derivation of modulation instability was published by V. I. Bespalov and V. I. Talanov in 1966.[6] Modulation instability is a possible mechanism for the generation of rogue waves.[7][8]