Quantum Statistical Properties of Resonant Radiation Scattered on Excited Systems (Report‪)‬

1. Introduction The quantum excited systems possess remarkable properties. They manifest themselves most prominently in lasers and masers, which were created in the middle of the last century. The theory of these devices was elaborated by W. Lamb [1] on the base of a semi classical theory of radiation which deals with classical electromagnetic field. Later the quantum theory was proposed [2]. It is possible to state omitting the fluctuations properties that both the semi classical and the quantum theories result practically in the same results for quantum means values. Such a fact resulted in overestimation of the applicability of the semi-classical theory. In 1966 year, Ch. Koester predicted the effect of light enhancement [3] by selective reflection of resonant radiation from excited media. All efforts of quantitative explaining this effect on the base of semi-classical theory of radiation discussed in monograph [4] were unsuccessful [5,6]. It was shown later that quantum field theory should be used instead [7], but the mathematically problems on this way occurred very difficult [8]. The consequences of such a theory manifest themselves on a macroscopic level. The correct description of stimulated radiation plays an especial role when the resonant reflection of light from excited media is considered. Nevertheless, there are recent works [9] which make use the semiclassical theory and Fresnel's formulae to describe the reflection of light from enhanced media.