Observation of slow light propagation in saturable erbium doped fiber via transient fluorescence at the fiber side

Abstract

Erbium-doper fiber (EDF) is a flexible and promising model medium for investigation of the slow/fast light propagation in saturable optical materials. The experiments are usually performed in the spectral range 1480-1570 nm of the absorption/gain of Er 3+ ions using the input power of a sub-mW scale. Conventional experimental configuration allows one to observe, however, the input and the output pulse profiles only. We report an original nondestructive technique for observation of a spatial propagation of the pulses via observation of the transient fluorescence excited by the propagating light-pulses at the fiber side, from which we are able to reconstruct how does the fractional delay and the amplitude of the propagating pulses change along the fiber. Results of a numerical simulation of the nonlinear pulse propagation performed for a saturable two-level medium in low contrast approximation proved to be in a reasonable agreement with the experimental observations.