The cross section for photoabsorption by a semiconductor quantum dot has been calculated with the previously obtained densities of electrons in the surface traps, conduction electrons, and electrons in unionized impurities. It has been found that the total photoabsorption cross section has two characteristic maxima corresponding to absorption by conduction electrons and by electrons in traps in the bulk of the quantum dot. The contribution of electrons in traps on the surface of the quantum dot is small and manifests itself only in a relatively short-wavelength range of the spectrum.
The development of methods of generation of ultrashort pulses (USP) of femto- and attosecond duration ranges with controlled parameters necessitates the theoretical study of features of their interaction with a matter . Among such features that do not exist in case of “long” pulses should first of all be the nonlinear dependence of the photoprocess probability W on the USP duration (τ)  as well as the dependence on the carrier phase with respect to the pulse envelope (φ) [3-4]. It should be noted that if the dependence of the probability W on the phase φ manifests itself either only for very short pulses, when ωτ < 1 (ω is carrier frequency of the pulse), or in case of a nonlinear photoprocess , the function W(τ) can differ from a linear function in the limit ωτ> 1 too for fields of moderate strength, when the perturbation theory is applicable .
The presentation is devoted to the theoretical investigation of nonlinear scattering of ultrashort electromagnetic pulses (USP) on two-level quantum system. <p> </p>We consider the scattering of several types of USP, namely, so called corrected Gaussian pulse (CGP) and cosine wavelet pulse. Such pulses have no constant component in their spectrum in contrast with traditional Gaussian pulse. It should be noted that the presence of constant component in the limit of ultrashort pulse durations leads to unphysical results. <p> </p>The main purpose of the present work is the investigation of the change of pulse temporal shape after scattering as a function of initial phase at different distances from the target. Numerical calculations are based on the solution of Bloch equations and expression for scattering field strength via dipole moment of two-level system exposed by the action of incident USP.<p> </p> In our calculation we also account for the influence of refracting index of the air on electric field strength in the pulse after scattering.