  We review recent statistical mechanical approaches to multimode laser theory.
The theory has proved very effective to describe standard lasers. We refer of
the mean field theory for passive mode locking and developments based on Monte
Carlo simulations and cavity method to study the role of the frequency matching
condition. The status for a complete theory of multimode lasing in open and
disordered cavities is discussed and the derivation of the general statistical
models in this framework is presented. When light is propagating in a
disordered medium, the system can be analyzed via the replica method. For high
degrees of disorder and nonlinearity, a glassy behavior is expected at the
lasing threshold, providing a suggestive link between glasses and photonics. We
describe in details the results for the general Hamiltonian model in mean field
approximation and mention an available test for replica symmetry breaking from
intensity spectra measurements. Finally, we summary some perspectives still
opened for such approaches.
