A saturable absorber, coherent population oscillations, and slow light

The paper presents a critical analysis of publications on one of the methods of creating so-called slow light (light with an anomalously low group velocity) arising due to a high steepness of the refractive index dispersion curve. The method employs, for this purpose, the effect of coherent population oscillations accompanied by burning of a narrow spectral hole in the homogeneously broadened absorption spectrum. The interpretation of the experimental data in the studies under consideration is based on the analysis of the response of a nonlinear medium to a low-frequency intensity modulation of the propagating light beam. We show that all the observations of these papers can be easily interpreted in the framework of the simplest model of a saturable absorber and have nothing to do with the hole burning effect or group velocity reduction.