Stability of screening solitons in photorefractive media

Normal mode stability of both rectilinear and self-bending photorefractive screening solitons is considered. In each case, the Evans function procedure is used to investigate stability and to search for internal modes. For the rectilinear case, a standard Evans function procedure is applied. However, in the self-bending case the asymptotic form of the eigenvalue problem is a system of Airy equations, instead of the usual system of constant coefficient differential equations. To overcome this difference, a modified version of the Evans function method, using Airy functions rather than exponentials, is implemented and applied. The results confirm stability and give an internal mode pattern in good agreement with full numerical integration.