Criterion for light localization in random amplifying media

Dimensionless conductance for light propagating through a random medium with amplification tends to diverge with an increase of gain. This raises questions on the applicability of the localization criteria based on this quantity. To circumvent this problem, we study the properties of the ratio between the transmission (conductance) and the energy stored in the random medium. We argue that the generalized conductance gG=g·(E0/E)—conductancegG=g·(E0/E)—conductance normalized by the energy buildup (ratio between energy stored in the medium with gain EE to that in the passive system E0E0)—may be a convenient quantity on which a localization criterion can be built.