Gauss-Laguerre modes: a "sensible" basis for laser dynamics

Modal decomposition of a system of partial differential equations is a useful analytical and numerical tool. In particular, it is often desirable to describe complex spatio-temporal behaviours by restricting the analysis to the interaction of few suitably chosen modes. We show how the Gauss-Laguerre modes have this property for many laser states, and are thus a "sensible" basis onto which to project the laser equations.