Small-scale instability of elliptically polarised waves in a medium with cubic nonlinearity

The boundary problem on the development of a smallscale instability of arbitrarily polarised plane waves is solved. The influence of polarisation on the spatial-perturbation gain is analysed. The maximally allowable (i.e., causing no destruction of a nonlinear medium) average intensity at a specified input noise is determined for arbitrary polarisation. (nonlinear optical phenomena)