A coupled mode approach to modulation instability and envelope solitons

Abstract

Nonlinear media that support envelope solitons are known to exhibit modulation instability; the modulation depth of an amplitude modulated carrier increases spontaneously and it breaks up into isolated pulses. This paper presents a simple coupled mode approach that shows the transfer of power from the carrier to the sidebands, and clearly brings out the roles played by dispersion and nonlinearity. Using this approach it is shown that line acoustic waves should exhibit this instability; the growth rate of the instability is large enough that an experimental demonstration seems feasible.