In the work we investigate synthesis of aluminum nitride films using reactive ion plasma deposition in oxygen/nitrogen gas mixture for application as optical elements for power semiconductor lasers. The experimental refractive index of synthesized AlNO films is dependent on oxygen composition and is decreasing in diapason from 1.76 to 2.035 at elevation of the oxygen fraction.It is shown that the AlN films synthesized by pure nitrogen plasma are polycrystalline and textured. The oxygen presence in discharging gas results to growth of amorphous phase of the AlNO film.

AbstractIn the work we investigate synthesis of aluminum nitride films using reactive ion plasma deposition in oxygen/nitrogen gas mixture for application as optical elements for power semiconductor lasers. The experimental refractive index of synthesized AlNO films is dependent on oxygen composition and is decreasing in diapason from 1.76 to 2.035 at elevation of the oxygen fraction.It is shown that the AlN films synthesized by pure nitrogen plasma are polycrystalline and textured. The oxygen presence in discharging gas results to growth of amorphous phase of the AlNO film.

The operating characteristics of semiconductor quantum-well lasers, calculated with consideration for an increase in the internal optical loss in the waveguide region with increasing pump current, are presented. The condition of global electroneutrality in the structure is used. This condition consists in that the total charge of electrons in the 2D active region (quantum well) and bulk waveguide region (optical confinement layer) is equal to the total charge of holes in these two regions. Good agreement between the calculated and experimentally determined light–current characteristics is obtained.

На основе методов высокоразрешающей рентгеновской дифракции, рамановской и фотолюминесцентной спектроскопии исследованы структурные, оптические и энергетические свойства эпитаксиальных гетероструктур AlxGa1-xAs : Mg/GaAs(100) с различной степенью легирования магнием. Показано, что подбором технологических условий в твердом растворе AlxGa1-xAs : Mg может быть достигнут не только различный тип проводимости, но и существенно различная концентрация носителей заряда в эпитаксиальной пленке. DOI: 10.21883/FTP.2017.01.8342

IR and UV spectroscopy is used to study the properties of nanostructured aluminum nitride films obtained via reactive ion-plasma sputtering on GaAs substrates with different orientations. Nanostructured thin (100–200 nm) films of cubic aluminum nitride with optical bandgaps of ~5 eV and refractive indices varying from 1.6 to 4.0 in the wavelength range of ~250 nm are fabricated. Growth on a misoriented GaAs(100) substrate (4° with respect to the [110] plane) makes it possible to synthesize AlN films with smaller grains and higher refractive indices (n ~ 4). It is shown that misoriented GaAs substrates allow us to control the morphology, surface composition, and optical functional characteristics of AlN/GaAs heterophase systems.

We have examined the two-state operation process of the high-power edge-emitting lasers based on AlGaAs/InGaAs/GaAs heterostructure with a thick (90 Å) quantum well in the active region. It has been demonstrated that the laser emission spectrum can be switched between spectral lines corresponding to different optical transitions between the quantum states in the active region. The switching process is governed either by pump current or by temperature. The dynamic characteristics of the switching laser pumped with 100 ns current pulses have been investigated and explained. It has been shown that the current density dependence of internal optical loss can cause the current-initiated switching. The temperature impact is much more important and consists in the charge carrier redistribution in the quantum well. The registered optical power near the switching point was near 2 W in continuous wave and 15 W in pulse mode of operation.

Продемонстрирована полностью оптическая ячейка на основе лазерных гетероструктур на длину волны 905 nm, работающая в режиме модулятора выходной оптической мощности за счет управляемого переключения генерации между модами резонатора Фабри-Перо и высокодобротной замкнутой модой. Достигнуты времена переключения 1.2 ns и менее при модулируемой мощности 1.6 W. DOI: 10.21883/PJTF.2017.02.44184.16247

Экспериментально и теоретически изучено воздействие вводимых извне переменных деформаций на поляризационные свойства излучения лазера In28Ga72As/GaAs на квантовой яме при комнатной температуре. Проведен анализ поляризационных эффектов при различных величинах превышения рабочим током порогового. Получены данные о величине энергии расщепления уровней легких и тяжелых дырок в квантовой яме исследованной структуры. Экспериментально доказано, что эффективность воздействия переменной деформацией на поворот поляризации существенно возрастает с увеличением ширины квантовой ямы. Работа поддержана РФФИ (грант N 11-02-00729) и научными программами Президиума РАН. DOI: 10.21883/FTT.2017.09.44837.062x

The effect of externally introduced variable strains on the polarization properties of quantum-well In28Ga72As/GaAs laser radiation at room temperature is studied experimentally and theoretically. An analysis of the polarization effects at various values of the excess of the working current over the threshold is performed. Data on the energy for the splitting of the levels of light and heavy holes in the quantum well of the structure under consideration are obtained. It is experimentally proven that the effectiveness of the action of a variable strain on the polarization twist substantially increases with increasing quantum well width.

Представлены результаты расчетов рабочих характеристик полупроводниковых лазеров на квантовых ямах с учетом роста внутренних оптических потерь в волноводной области с увеличением тока накачки. Использовано условие глобальной электронейтральности в структуре, которое заключается в равенстве суммарного заряда электронов в активной и волноводной областях суммарному заряду дырок в этих двух областях. Получено хорошее согласие измеренной и рассчитанной ватт-амперных характеристик. DOI: 10.21883/FTP.2017.07.44661.8522

The effect of a local current turn-on in the heterostructure plane has been observed for low-voltage lasers-thyristors. It was shown that the spatial dynamics of the current-turn-on region is determined by the blocking voltage and the control current amplitude. For the first mode (blocking voltages up to 15 V), the current nonuniformity in the heterostructure plane is determined by the flux distribution of the spontaneous emission from the active region in the laser part to the side of the p-base of the phototransistor part of the heterostructure. The transition to the second mode (blocking voltages exceeding 15 V) is due to the sharp rise in the generation rate of excess carriers in the p-base of the phototransistor part of the heterostructure. In this case, the size of the region in which the original current turn-on occurs decreases to 70 μm. It was found that the rate at which the current-turn-on region expands depends on the working conditions of the laser part of the laser-thyristor and is 50 and 20 μm/ns for the spontaneous generation and lasing modes, respectively. It was also found that the spatial dynamics of the current determines the spatial dynamics of the laser light turn-on in the lateral waveguide and the emission efficiency in generation of short (<10 ns) laser pulses. It was demonstrated that, at low control currents, the main contribution to the decrease in the emission efficiency is made by the residual optical loss in the turned-off part of the laser-thyristor. At higher amplitudes of the control current, the emission efficiency grows due to the decrease in the residual loss in the turned-off part of the laser-thyristor, which made it possible to raise the peak power to 47 W for 100-ns laser pulses.

All-optical cells based on AlGaAs/GaAs/InGaAs laser heterostructures for a 905-nm wavelength have been developed, which operate in the regime of optical-power modulation by means of controlled generation switching between the Fabry–Perot cavity modes and high-Q closed mode. At a modulated power of 1.6 W, a mode-switching time of 1.2 ns and smaller is achieved.

The structural, optical, and energy properties of epitaxial Al x Ga 1 – x As:Mg/GaAs(100) heterostructures at different levels of doping with Mg are studied by high-resolution X-ray diffraction analysis and Raman and photoluminescence spectroscopies. It is shown that, by choosing the technological conditions of Al x Ga 1– x As:Mg alloy production, it is possible to achieve not only different conductivity types, but also substantially different charge-carrier concentrations in an epitaxial film.

Threshold characteristics of a semiconductor quantum-well (QW) laser are calculated using the global electroneutrality condition, which includes charge carriers both in the active and waveguide regions and thus presents an equality of the total charge of electrons to the total charge of holes in these two regions. It is shown that at the lasing threshold, the densities of electrons in the QW and the waveguide region are not equal to the densities of holes in these regions, i.e., the local electroneutrality condition is violated in each of the regions. Depending on the velocities of the carrier capture from the waveguide region into the QW, the electron density can be either higher or lower than the hole density (both in the QW and in the waveguide region). The charge of the carriers of each sign in the waveguide region is shown to be greater than that in the QW.

Semiconductor lasers based on MOCVD-grown AlGaInAs/InP separate-confinement heterostructures are studied. It is shown that raising only the energy-gap width of AlGaInAs-waveguides without the introduction of additional barriers results in more pronounced current leakage into the cladding layers. It is found that the introduction of additional barrier layers at the waveguide–cladding-layer interface blocks current leakage into the cladding layers, but results in an increase in the internal optical loss with increasing pump current. It is experimentally demonstrated that the introduction of blocking layers makes it possible to obtain maximum values of the internal quantum efficiency of stimulated emission (92%) and continuouswave output optical power (3.2 W) in semiconductor lasers in the eye-safe wavelength range (1400–1600 nm).

1550nm-lasers based on MOCVD-grown heterostructures are investigated. It is determined, that additional barrier layers grown between waveguide and cladding layers block carrier leakage into the cladding layers but results in internal optical loss rise with drive current increase. It is demonstrated that incorporation of barrier layers allows attaining 92% internal quantum efficiency and 3.2W CW RT output optical power.

The spectral characteristics of a high-power semiconductor laser with an external cavity in which longitudinal-mode selection is implemented by means of a holographic volume Bragg grating recorded in photo-thermo-refractive glass are investigated. Mode selection leads to narrowing of the spectrum of the laser diode from an initial width of 6 nm to 5 Å. In the narrowed spectrum, a fine structure representing a set of eigenmodes that correspond to the length of a laser chip is resolved. The number of these modes is limited by the width of the spectral selectivity curve of the grating. It is shown that insertion of the grating into the cavity leads to severalfold enhancement of the grating selectivity. It is demonstrated that the implemented external-cavity design makes it possible to smoothly tune the laser emission wavelength in a 10-nm range.

Three laser structures with a single strained InGaAs quantum well of different depths and a GaAs or Al0.1Ga0.9As waveguide region are grown by metal-organic chemical vapor deposition. Using the experimentally determined values of the threshold current density and internal differential quantum efficiency, the velocity of electron capture into the quantum well is calculated for each of these structures. It is found that the capture velocity into deep quantum wells is significantly lower than into shallow ones.

The room-temperature generation of multiperiod quantum-cascade lasers (QCL) at a wavelength of 5.8 μm in the pulsed mode is demonstrated. The heterostructure of a quantum-cascade laser based on a heterojunction of InGaAs/InAlAs alloys is grown by molecular-beam epitaxy and incorporates 60 identical cascades. The threshold current density of the stripe laser 1.4 mm long and 22 μm wide is ~4.8 kA/cm 2 at a temperature of 303 K. The maximum power of the optical-radiation output from one QCL face, recorded by a detector, is 88 mW. The actual optical-power output from one QCL face is no less than 150 mW. The results obtained and possible ways of optimizing the structure of the developed quantum-cascade lasers are discussed.