Absorption of high-intensity visible or near-IR pulsed laser radiation at free electrons in crystals is calculated in the modified resonance approximation. The probabilities $W_{exc}$ of intraband transitions with a change in the electron energy by $\hbar(\omega\pm\omega_l)$, where $\omega$ is the radiation frequency and $/omega_l$ the frequency of longitudinal optical phonons involved in the process, are derived. It is shown that specific electron–phonon Rabi oscillations with the frequency $\Omega_R$ can occur and radiation is absorbed only until the point in time $\tau_1$, at which the first maximum in the dependence $W_{exc} (t)$, where t is the time elapsed from the beginning of the laser pulse, is reached. It is shown that, in the case of prebreakdown radiation intensities, the processes of high orders in field of the radiation wave substantially influence $W_{exc}$, $\tau_1$, and $\Omega_R$.

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Вычислены вероятности различных типов оптических процессов, участвующих в формировании фотонной лавины в гетероструктурах типа I с глубокими квантовыми ямами. В числе этих процессов двухэлектронные переходы с участием фотона, фотопереходы между электронными состояниями подзон размерного квантования и непрерывного зонного спектра, двухфотонные межзонные переходы в квантовых ямах. Полученные вероятности будут использованы в следующих частях работы для анализа кинетики фотонной лавины.

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The probabilities W_{exc} of photon- and TA-phonon-assisted intraband electronic transitions in a covalent crystal are derived. It is shown that, at prebreakdown intensities of light, specific electron-phonon Rabi oscillations can be generated, with the frequency influenced by the processes of high order in field of the light wave. As in the case of previously considered optical-phonon-assisted processes, absorption of light lasts for the time τ1, in which the first maximum in the dependence W_{exc}(t), where t in time reckoned from the beginning of the laser pulse, is reached.