The effects of local fields on laser gain of composite optical materials

We develop a simple theoretical model for calculating the effective linear susceptibility of composite optical materials with a gain resonance in one of their components. We distinguish two cases of resonant components: the case of “pure resonant emitters,” in which all the atoms or molecules of the resonant medium are of the same sort, and the case of “resonant emitters in a background,” in which only a fraction of the molecules or atoms comprising the resonant component of a composite material are in resonance with the optical field. Analysis of the model suggests that local‐field effects in composite materials can provide a useful means for controlling the optical properties of laser gain media.