Powerful picosecond optical pumping of the GaAs heterostructure layer causes the generation of stimulated picosecond emission in it. Due to its high intensity, the emission induces a Bragg grating of the electron population in the active region of the layer, making the latter an active photonic crystal. In the emission field, the inverse population of electrons oscillates with time, which should lead to spatiotemporal modulation of the emission and this population. It has been discovered that if the distance Y between the end of the heterostructure and the center of the active medium and the geometric parameters of the indicated modulation and movement of emission in the photonic crystal satisfy certain conditions, then dimensional resonance occurs - a maximum of modulation of the dependence of the energy of emission emerging from the end on Y and on pump energy appears locally.

The review presents the third part of the experimental study of emission and the optoelectronic effects excited by it. At the beginning of a powerful optical picosecond pumping of the GaAs layer of the AlxGa1 – xAs–GaAs–AlxGa1 – xAs heterostructure, a picosecond emission has occurred in it. It has been experimentally proved that this is amplified spontaneous (stimulated) emission with the propagation specifics in the heterostructure. It has been shown that the electron–hole plasma is maintained in a “threshold” state with an inversion of the electron population in a narrow energy range because of high emission intensity. In this regard, the electron temperature and therefore, their distribution between valleys, etc., becomes uniquely related to their density. It has been found that limiting the inversion meant the emission amplification saturation when the amplification is limited by the energy transport of charge carriers to the levels from which they are forced to recombine. It has been determined that the transport being slowed down by the heating of carriers because of their interaction with emission determines the dynamics of the emission as a whole and its spectral components when the temperature of the carriers is related to their density.

The review presents the third part of the experimental study of emission and the optoelectronic effects excited by it. At the beginning of a powerful optical picosecond pumping of the GaAs layer of the AlxGa1 – xAs–GaAs–AlxGa1 – xAs heterostructure, a picosecond emission has occurred in it. It has beenexperimentally proved that this is enhanced spontaneous (stimulated) emission with the propagation specifics in the heterostructure. It has been shown that the electron–hole plasma is maintained in a “threshold” state with an inversion of the electron population in a narrow energy range because of high emission intensity. In this regard, the electron temperature and therefore, their distribution between valleys, etc., becomes uniquely related to their density. It has been found that limiting the inversion meant the emission amplification saturation when the amplification is limited by the energy transport of charge carriers to the levels from which they are forced to recombine. It has been determined that the transport being slowed down by the heating of carriers because of their interaction with emission determines the dynamics of the emission as a whole and its spectral components when the temperature of the carriers is related to their density.

— The review presents the third part of the experimental study of emission and the optoelectronic effects excited by it. At the beginning of a powerful optical picosecond pumping of the GaAs layer of the Al x Ga 1 – x As–GaAs–Al x Ga 1 – x As heterostructure, a picosecond emission has occurred in it. It has been experimentally proved that this is amplified spontaneous (stimulated) emission with the propagation specifics in the heterostructure. It has been shown that the electron–hole plasma is maintained in a “threshold” state with an inversion of the electron population in a narrow energy range because of high emission intensity. In this regard, the electron temperature and therefore, their distribution between valleys, etc., becomes uniquely related to their density. It has been found that limiting the inversion meant the emission amplification saturation when the amplification is limited by the energy transport of charge carriers to the levels from which they are forced to recombine. It has been determined that the transport being slowed down by the heating of carriers because of their interaction with emission determines the dynamics of the emission as a whole and its spectral components when the temperature of the carriers is related to their density.

The real-time measured envelopes of high-power picosecond optical pumping and of the intrinsic stimulated picosecond emission of a thin GaAs layer are compared. The emission duration excess over the pump duration is explained on the basis of negative feedback between the emission intensity and carrier heating by this emission. The main parameter of this duration excess is the characteristic carrier cooling time slowed down due to carrier heating by emission. The effect of this time on renormalization of the band gap due to the Coulomb interaction of carriers is also noted. The part of the concept of the picosecond dynamics of the intense stimulated emission of GaAs, which has been obtained to date in our works with co-authors, is given in Conclusions.

Во время мощной оптической пикосекундной накачки слоя GaAs гетероструктуры AlxGa1-xAs-GaAs- AlxGa1-xAs в нем возникает стимулированное пикосекундное излучение. Экспериментально выявлено, как при насыщении усиления излучения максимальная плотность энергии его спектральной компоненты и время достижения этого максимума зависят от энергии фотона, параметров усиления и релаксации компоненты. Из этих зависимостей следует, что на указанные плотность и время влияет замедление транспорта неравновесных носителей в энергетическом пространстве. Замедление вызвано взаимодействием носителей с излучением. Установлено, что при приближении к нулю диаметра активной области измеренное характерное время релаксации компоненты стремится к теоретическому универсальному остаточному времени релаксации, затянутому из-за указанного замедления транспорта. Ключевые слова: стимулированное пикосекундное излучение, арсенид галлия, спектральные компоненты излучения, коэффициент усиления, характерное время релаксации излучения, насыщение усиления, энергетический транспорт носителей заряда.

A new, experimentally found phenomenon of quantum optics is described. In the beginning of high-power picosecond optical pumping of the GaAs layer in a heterostructure, intense picosecond stimulated emission is generated in this layer. The envelope of the fundamental absorption spectrum becomes modulated. This modulation cyclically changes with time, reflecting the radiation-excited deviation from the Fermi electron distribution, oscillating in time and energy space. The corresponding electron oscillations lead to the temporal modulation of emission. The investigation of this phenomenon revealed, along with other things, some fundamental processes, which should be explained in terms of the nonlinear optics of semiconductors; at the same time, they made it possible to explain some instabilities of the semiconductor laser radiation.

During high-power optical picosecond pumping of the GaAs layer of the Alx Ga1−x As−GaAs−Alx Ga1−x As heterostruc- ture, stimulated picosecond emission arises in it. It has been experimentally revealed how, upon saturation of the emission gain, the maximum energy density of its spectral component and the time to reach this density depend on the photon energy, on the parameters of the amplification and relaxation of the component. It follows from these dependences that the indicated density and time are influenced by the slowing down of the transport of nonequilibrium carriers in the energy space. The slowdown is caused by the interaction of carriers with emission. It has been found that as the diameter of the active region approaches zero, the measured characteristic relaxation time of the component tends to the theoretical universal residual relaxation time prolonged due to the indicated transport slowdown.

During high-power optical picosecond pumping of the GaAs layer of an AlxGa1 – xAs–GaAs–AlxGa1 – xAs heterostructure, stimulated picosecond emission arises in it. It has been revealed experimentally how, upon gain saturation of the emission, the maximum energy density of the spectral component of emission and the time for reaching this maximum depend on the photon energy and the gain and relaxation parameters of the component. These dependences imply that these density and time are affected by the slowdown of the transport of nonequilibrium carriers in the energy space. This slowdown is caused by the interaction of carriers with emission. It has been found that as the diameter of the active region tends to zero the measured characteristic relaxation time of the component tends to a theoretical universal residual relaxation time, which is prolonged due to the indicated slowdown of transport.

At the beginning of high-power optical picosecond pumping of the GaAs layer of the AlxGa1 – xAs–GaAs–AlxGa1 – xAs heterostructure, stimulated picosecond emission appears in it. The energy density of each spectral component of emission in its active medium increases with time exponentially until gain saturation and then increases linearly. In this work, it is experimentally determined, depending on which parameters of the spectral component of the emission and according to what law, the following changes (a) the time (counted from the beginning of stimulated emission) after which the exponential increase is replaced with a linear one, (b) the energy density of the component at the moment of the transition, and (c) the gain at the stage of linear increase in the component energy density. In the Conclusions, the phenomena observed in our work during gain saturation are summarized.

В начале мощной оптической пикосекундной накачки слоя GaAs гетероструктуры AlxGa1-xAs-GaAs-AlxGa1-xAs в нем возникает стимулированное пикосекундное излучение. Возрастание со временем плотности энергии каждой спектральной компоненты излучения в ее активной среде происходит экспоненциально до насыщения усиления, далее возрастание линейное. В настоящей работе экспериментально определено, в зависимости от каких параметров спектральной компоненты излучения и по какому закону меняется: (а) время (отсчитываемое от начала стимулированного излучения), через которое происходит переход от экспоненциального возрастания к линейному; (б) плотность энергии компоненты в "момент" перехода; (в) коэффициент усиления на этапе линейного возрастания плотности энергии. В Заключении суммируются явления при насыщении усиления, обнаруженные в наших работах. Ключевые слова: стимулированное пикосекундное излучение, арсенид галлия, спектральные компоненты излучения, характерное время релаксации излучения, насыщение усиления, энергетический транспорт носителей заряда, скорость вынужденной рекомбинации.

При мощной пикосекундной оптической накачке тонкого слоя GaAs в нем образуется интенсивное пикосекундное стимулированное излучение. Спектр излучения представляет собой световой континуум. На базе результатов предыдущих экспериментальных работ сделано следующее. Получены оценки: (а) длин усиления спектральных компонент излучения, т. е. различающихся между собой расстояний, на протяжении которых в активной среде, созданной накачкой, усиливаются различные компоненты излучения; (б) зависимости характерного времени релаксации компонент излучения от их длин усиления. Показано, что спектр произведения длины усиления на коэффициент усиления связывает линейно спектры спонтанного и стимулированного излучений GaAs. Эта связь установлена при насыщении усиления, о котором свидетельствует провал в спектре усиления, "выжженный" интенсивным излучением. Ключевые слова: стимулированное пикосекундное излучение, спектральные компоненты излучения, длина усиления, характерное время релаксации, насыщение усиления, связь стимулированного и спонтанного излучений, арсенид галлия.

The high-power picosecond optical pumping of a thin GaAs layer generates intense picosecond stimulated emission. The emission spectrum is a light continuum. Based on the results of previous experimental work, the following is carried out. (a) The amplification lengths of the emission spectral components, i.e., the different distances over which different emission components are amplified in the active medium produced by pumping and (b) the dependences of the characteristic relaxation time of emission components on their gain lengths are estimated. It is shown that the spectrum of the product of the gain length and the gain linearly relates the spectra of the spontaneous and stimulated emission of GaAs. This relation is established upon gain saturation which is evidenced by a dip in the gain spectrum, "burned out" by intense emission.

Во время мощной оптической пикосекундной накачки тонкого слоя GaAs, входящего в состав гетероструктуры AlxGa1-xAs-GaAs-AlxGa1-xAs, в нем возникает интенсивное стимулированное пикосекундное излучение. При анализе измеренных в реальном времени импульсов спектральных компонент излучения установлены коэффициенты экспоненциального, потом линейного усиления компонент на фронте. При этом обнаружено влияние на фронт компонент, оказываемое нагревом носителей заряда излучением. Получена зависимость длительности компоненты (FWHM) от характерных времен возрастания на фронте и релаксации (тоже замедленной нагревом носителей излучением) на спаде компоненты. Ключевые слова: стимулированное пикосекундное излучение, арсенид галлия, спектральные компоненты излучения, коэффициент усиления, характерное время возрастания излучения, характерное время релаксации излучения, разогрев носителей заряда, линейное усиление.

Сравниваются измеренные в реальном времени огибающие мощной пикосекундной оптической накачки и собственного стимулированного пикосекундного излучения тонкого слоя GaAs. Объяснение превышения длительности излучения над длительностью накачки базируется на отрицательной обратной связи между интенсивностью излучения и разогревом носителей этим излучением. Главным параметром указанного превышения длительности является характерное время охлаждения носителей заряда, замедляемое из-за разогрева носителей излучением. Отмечается влияние этого времени и на перенормировку запрещенной зоны из-за кулоновского взаимодействия носителей. Та часть представления о пикосекундной динамике интенсивного стимулированного излучения GaAs, которая получена к настоящему моменту в наших с соавторами работах, дана в Заключении. Ключевые слова: стимулированное пикосекундное излучение, длительность пикосекундного излучения, разогрев носителей заряда излучением, время охлаждения носителей заряда, энергетический транспорт носителей заряда, перенормировка запрещенной зоны, пикосекундная динамика излучения.

It was shown that the modulation of the spectrum of stimulated picosecond emission generated in the AlxGa1-xAs–GaAs–AlxGa1-xAs waveguide heterostructure upon optical pumping of GaAs, and a number of previous experimental results become explainable under the assumption that emission forms a symmetric modification of the “Bragg” population lattice of nonequilibrium electrons GaAs. Boundary conditions defining the lattice design are proposed. In particular, in order to satisfy them, the lattice can only change discretely. The latter is consistent with a change in the modulation of the light absorption spectrum in GaAs, which reflects the modulation of population depletion created by emission in a high-quality heterostructure. The latter is consistent with a change in the modulation of the light absorption spectrum in GaAs, which reflects the modulation of population depletion created by emission. Inducing the lattice, i.e. burning out spatial holes, is one of the reasons for the multimode nature of emission, competition and switching of its modes, modulation of the gain spectrum (burning out frequency holes). The same is possible in a semiconductor laser, as in a waveguide.

It is shown that modulation of the spectrum of stimulated picosecond emission generated in an AlxGa1 – xAs–GaAs–AlxGa1 – xAs waveguide heterostructure upon the optical pumping of GaAs, as well as a number of previous experimental results, can be explained under the assumption that the emission forms a symmetric modification of the Bragg grating of the nonequilibrium electron population in GaAs. The boundary conditions determining the grating design are proposed. To satisfy them, the grating can change only discretely. The latter is consistent with a change in the modulation of the spectrum of light absorption in GaAs, which reflects the emission-stimulated modulation of the population depletion. Inducing the grating, i.e., spatial hole burning, is one of the reasons for the multimode character of the emission, competition and switching of its modes, and modulation of the gain spectrum (frequency hole burning). The same is possible in a semiconductor laser, as in a waveguide.

During the powerful picosecond optical pumping, intense stimulated picosecond emission arises in a thin GaAs layer. It was found that, firstly, the maximum emission intensity decreases with increasing diameter of the pump beam (the pump energy density is fixed). Secondly, this dependence is anticorrelated with the dependence on the diameter of the characteristic relaxation time of the emission. And this time, in turn, is associated with the characteristic cooling time of charge carriers, which is slowed down due to heating of the carriers by emission. As a result, the autocorrelation indicated in the title is revealed.

During the powerful picosecond optical pumping, intense stimulated picosecond emission arises in a thin GaAs layer. It is found that, first, the maximum emission intensity decreases as the diameter of the pump beam increases (while the pump energy density is fixed). Second, this dependence anticorrelates with the dependence of the characteristic relaxation time of the emission on the beam diameter. This time is related to the characteristic cooling time of charge carriers, which is slowed due to carrier heating by emission. This leads to the anticorrelation given in the title.

A brief review of experimental results is presented on discovery of a new nonlinear phenomenonpicosecond self-modulation of the fundamental absorption of a picosecond probe light pulse in a thin layer of GaAs that generates stimulated intense picosecond emission.It is explained by the synchronization of two modulations of the electron population of energy levels in the conduction band.One is created by the probing light.The other is created at the bottom of the zone by picosecond interband oscillations of electrons in the emission field and is transmitted up the zone to restore the detailed equilibrium of electron transitions with the radiation and absorption of LO phonons.Synchronization of modulations occurs in order to achieve similar detailed equilibrium.