Kinetics of Hole Burning in Inhomogeneously Broadened Spectra: the Origin of Nonexponentiality and Problem of Burning Efficiency Dispersion

High inhomogeneous broadening of impurity spectra in amorphous media reflects one type of dispersion, characteristic for disordered systems: dispersion of electronic transition frequency. In principle, there can exist a pronounced dispersion of other parameters: homogeneous line width (Γ), Debay-Waller factor (α), hole burning efficiency (ϕ), etc. The problem of the burning efficiency dispersion (BED) was extensively discussed in the recent years ([1-6] and references therein). The nonexponentiality of the burning kinetics was treated in some publications [1-3,6] as an evidence of such dispersion. But burning kinetics is always nonexponential in strongly inhomogeneously broadened systems, if a burning laser line width Δνl is much less then Γ. That was found experimentally and treated theoretically in one of the first publications on a hole burning [7] (see, also [8]). All other sources of the nonexponentiality are, in fact, additional to this one. So, it’s not easy to attain experimentally the BED parameters on such background. The procedure of a numerical fit ting of the burning kinetic with BED, developed in [4,5], is correct, but it looks unreliable due to many fitting parameters.