Avalanche-like behavior of up-conversion luminescence by nonlinear coupling of pumping rates

Here we report and discuss the avalanche-like up-conversion behavior in absence of the avalanche. We experimentally observed significant changes in the slope of the curve for the intensity dependence of up-conversion luminescence of erbium ions in green band on the pump intensity of the diode laser. Such changes are typical for the photon avalanche. However, the concentration of erbium ions is insufficient for an efficient exchange of energy between them, and excitation of a photon avalanche is not possible. Using a simple three-level approximation of the up-conversion process model, we have shown that the observed avalanche-like luminescence process can also occur in the absence of a photon avalanche due to the non-linear relation between the efficiency of two pumping channels of erbium ion caused by intensity dependence of the absorption.