Spontaneous (two-pulse) photon echo in the nanoscale structure of self-organized quantum dots

We consider the coherent response of a medium with quasi-zero-dimensional structural units in the form of a photon echo upon resonant selective pulsed excitation of interband optical transitions, the inhomogeneous broadening of which is largely determined by the polydisperse composition of the nanocomposite. The process of formation of a photon echo is analyzed, when optical excitation leads to the formation of exciton complexes by resident electrons, which are localized in nanosized microcrystals in the limiting cases of strong and weak size quantization. By studying the coherent dynamics of the components of the pseudospin electric dipole vector, an expression is derived for the macroscopic specific polarization at the moment of emission of the photon echo signal. The consideration is carried out for a model nanocomposite medium on the example of a dielectric matrix with a system of semiconducting spherical inclusions (spherical quantum dots), the distribution over the radii of which is described by the Lifshitz-Slyozov formula.