Interperiods electron transport coherences in quantum-cascade structures

Results of electron transport investigation in the quantum-cascade structures are reported. Mathematical model connecting optical characteristic and electron transport have been developed by us applying the density matrix theory. It is shown that series of electron coherent transitions in the injector leads to coherent coupling of adjacent active regions. Such an interperiod coherence becomes apparent as changes in frequency and amplitude of oscillations of observables at the fetmosecond scale.