Pulsed Semiconductor Research Articles

Thermo-diffusion of excited photothermal semiconductor under laser pulse and ramp heating with acoustic pressure

The goal of this work is to provide a novel mathematical model that explains how certain physical variables propagate (acoustic-thermal-mechanical diffusive) as waves in a photoexcited non-Gaussian laser pulse semiconductor medium. Under the impact of acoustic pressure, the isotropic and homogeneous semiconductor medium is discussed concerning the fundamental equations according to charge carrier recombination processes with optoelectronic properties. Given the impact that relaxation times have on the governing equations. Laplace transforms were utilized in a one-dimensional (1D) context to examine essential non-dimensional properties such as displacement, stress components, carrier density, temperature, and acoustic pressure in order to mathematically answer the required problem. By imposing specific initial and boundary conditions, inverse Laplace transformations were employed to generate precise solutions for the numerical modeling of different physical quantities depicted graphically. The graphical representation of wave propagation data was followed by a theoretical analysis and interpretation, emphasizing the influence of other factors (such as heat rise time, relaxation times, and laser pulse effects) on the observed occurrences.

STUDY OF THE EFFICIENCY OF SEARCH ALGORITHM FOR SELECTING THE MAXIMUM POWER OF SOLAR PANELS USING A DC-DC BOOST CONVERTER

The results of the study of the effectiveness of the search algorithm for selecting the maximum power from solar panels by a step-up pulse semiconductor converter in the conditions of dynamic changes in illumination are presented. An analysis of the mathematical model of solar panels was carried out, which determines the volt-ampere characteristics and power characteristics of the solar panel as a function of its voltage. A search algorithm for determining the mode of operation of the semiconductor converter, which ensures the mode of maximum power selection from solar panels, has been developed. This algorithm can be applied to various types of converters, in which the value of the input current depends on the filling factor of pulse-width modulation. In the Matlab software, a corresponding simulation model of the DC-DC boost converter, which selects the power of solar panels at different levels of solar radiation, was developed, with the help of which the efficiency of the developed algorithm was determined. In the course of the simulation, it was determined that the developed algorithm provides a fairly high efficiency of solar panel power extraction, which is a fairly high indicator compared to the described algorithms. It was determined that the dynamic properties of the semiconductor converter, which takes power from solar panels, directly affects the time of transition to the mode of taking maximum power. During the first switch-on, the output to the point of maximum power is about 1.2 seconds, in further operation, the transition occurs almost instantaneously for a time that corresponds to the time constant of the converter. Given that the processes of changing the level of sunlight take minutes, this time is acceptable.

Femtosecond pulsed laser technology and applications

This paper describes femtosecond pulsed laser technology and related applications. The focus is on two core femtosecond pulsed laser technologies: femtosecond pulsed laser generation and amplification. In the generation of femtosecond pulsed lasers, mode-locking techniques, Kerr-lens mode-locking, and semiconductor saturable absorber mirrors are presented; in the amplification of femtosecond pulsed lasers, chirped-pulse amplification and coherent synthesis techniques are presented. This paper analyses the applications of femtosecond pulsed lasers in both the biomedical and manufacturing sectors and gives the development trends as well as the challenges of femtosecond laser technology. Femtosecond lasers are now used in a wide range of applications. Femtosecond pulsed lasers will develop in the directions of high power, miniaturisation, intelligence and precision. Laser tweezers will become the new direction of development in the future.

Development of technology for creating high-voltage p0–n0 junctions based on GaAs

An optimal solution has been found to the problem of obtaining p0-n0 junctions based on lightly doped GaAs layers with high values of electrical parameters and specified thicknesses of base layers to create ultra-fast high-voltage pulsed three-electrode switches with a photon injection mechanism of minority charge carriers. A technology has been developed for the formation of high-voltage, powerful subnano-second photonic injection switches based on gallium arsenide and its solid solutions. The dependence of the current rise time, switching voltage and switching stability relative to the control pulse of high-voltage photonic injection switches in a wide current and frequency mode of their operation, its sensitivity to various external influences, as well as dependence on the thickness of the p0-layer, on the transmission coefficient, on breakdown voltage Uprobe of the high-voltage p0-n0 junction. The carried out studies and the obtained results indicate the prospects of using the developed high-voltage pulsed semiconductor devices in picosecond optoelectronics for pumping high-power laser and LED structures.

СПОСОБИ ПІДВИЩЕННЯ ЕНЕРГОЕФЕКТИВНОСТІ СПЕЦІАЛІЗОВАНИХ ПЕРЕТВОРЮВАЧІВ ЕЛЕКТРОЕНЕРГІЇ ДЛЯ СУЧАСНИХ ІМПУЛЬСНИХ ТЕХНОЛОГІЙ

The article examines the proposed power electronics devices with an assessment of their basic quality indicators and functional purpose. The following of these devices have been identified, the use of which increases the e nergy efficiency of electrical networks the most. It is shown that these devices, due to their improved functional and parametric data, are also widely used in electrical consumer devices. Here are some of the mentioned devices. Combined and Controlled Latour-Gretz Rectifiers, Magnetic Semiconductor Pulse Regulators, DC/DC Pulse Converters, DC/AC Converters, DC/AC Converters, Full Thyristor Transistor Switch - VTS, Controlled Magneto-Semiconductor Generator pulses, an improved structural diagram of a magnetic semiconductor pulse generator. It was concluded that the following quality indicators of the above devices are the most acceptable for increasing the energy efficiency of electrical networks on the part of devices that are powered by them: high efficiency; improved electromagnetic compatibility; protection against short circuits and switching overvoltages; controllability according to load requirements; buffer resistance against interruption of the input current. Ref. 7, fig. 7. Keywords: energy efficiency of electrical networks, combined and controlled Latour-Gretz rectifiers, magnetic semi-conductor regulators and pulse generators, pulse converters DC/DC, DC/AC.

LIDAR for Investigation of the Martian Atmosphere from the Surface

The lidar device as part of the meteorological complex of the ExoMars-2022 landing platform is designed to study Martian aerosol, the planetary boundary layer, and small-scale atmospheric turbulence. A miniature lidar based on a pulsed semiconductor laser and an avalanche photodiode in the photon counting mode will make it possible to obtain aerosol backscattering profiles along a vertical path from 10 to 1500 m during the day and from 15 to 10 000 m at night. In the passive mode, the sky brightness is measured in a narrow spectral range and in a narrow solid angle with a frequency of up to hundreds of hertz. The measured fluctuations can provide information about the turbulence of the daytime atmosphere and its relation to dust activity. In the paper we considered the scientific tasks of the experiment, the program of measurements on the surface of Mars and described in detail the components of the equipment and the features of their work.

LIDAR for Investigation of the Martian Atmosphere from the Surface

The lidar device as part of the meteorological complex of the ExoMars-2022 landing platform is designed to study Martian aerosol, the planetary boundary layer, and small-scale atmospheric turbulence. A miniature lidar based on a pulsed semiconductor laser and an avalanche photodiode in the photon counting mode will make it possible to obtain aerosol backscattering profiles along a vertical path from 10 to 1500 m during the day and from 15 to 10000 m at night. In the passive mode, the sky brightness is measured in a narrow spectral range and in a narrow solid angle with a frequency of up to hundreds of hertz. The measured fluctuations can provide information about the turbulence of the daytime atmosphere and its relation to dust activity. In the paper we considered the scientific tasks of the experiment, the program of measurements on the surface of Mars and described in detail the components of the equipment and the features of their work.

Designing a 1550 nm Pulsed Semiconductor Laser-Emission Module Based on a Multiquantum-Well Equivalent Circuit Model

The demand for eye-safe 1550 nm pulsed semiconductor laser-emission modules is increasing in the field of active laser detection, owing to their long range and high precision. The high power and narrow pulse of these modules can significantly improve the distance and accuracy of active-laser detection. Here, we propose an equivalent circuit model of a multiquantum-well laser based on the structure of a laser device. We developed a design method for 1550 nm pulsed semiconductor laser-emission modules according to the equivalent circuit model of an InGaAlAs laser. In this method, the module design was divided into laser chip and laser-driver levels for optimization and simulation. At the chip level, a high-output power laser chip with optimal cavity length and optical facet coating coefficients was obtained. At the laser-driver level, the model was applied to a drive circuit to provide direct narrow optical pulses. Finally, a laser-emission module was fabricated based on the optimal design results. In addition to the power-current features of the actual laser, the critical voltage of the emission module and laser pulses were tested. By comparing the test and simulation results, the effectiveness of the proposed method was confirmed.

Gain recovery dynamics in active type-II semiconductor heterostructures

Type-II heterostructures as active layers for semiconductor laser devices combine the advantages of a spectrally broad, temperature stable, and efficient gain with the potential for electrical injection pumping. Their intrinsic charge carrier relaxation dynamics limit the maximum achievable repetition rates beyond any constraints of cavity design or heat dissipation. Of particular interest are the initial build up of gain after high-energy injection and the gain recovery dynamics following depletion through a stimulated emission process. The latter simulates the operation condition of a pulsed laser or semiconductor optical amplifier. An optical pump pulse injects hot charge carriers that eventually build up broad spectral gain in a model (Ga,In)As/GaAs/Ga(As,Sb) heterostructure. The surplus energies of the optical pump mimic the electron energies typical for electrical injection. Subsequently, a second laser pulse tuned to the broad spectral gain region depletes the population inversion through stimulated emission. The spectrally resolved nonlinear transmission dynamics reveal gain recovery times as fast as 5 ps. These data define the intrinsic limit for the highest laser repetition rate possible with this material system in the range of 100 GHz. The experimental results are analyzed using a microscopic many-body theory identifying the origins of the broad gain spectrum.

Twin-core fiber sensor integrated in laser cavity

In this work, we report on a twin-core fiber sensor system that provides improved spectral efficiency, allows for multiplexing and gives low level of crosstalk. Pieces of the referred strongly coupled multicore fiber are used as sensors in a laser cavity incorporating a pulsed semiconductor optical amplifier (SOA). Each sensor has its unique cavity length and can be addressed individually by electrically matching the periodic gating of the SOA to the sensor’s cavity roundtrip time. The interrogator acts as a laser and provides a narrow spectrum with high signal-to-noise ratio. Furthermore, it allows distinguishing the response of individual sensors even in the case of overlapping spectra. Potentially, the number of interrogated sensors can be increased significantly, which is an appealing feature for multipoint sensing.

Semiconductor disk laser with a wavelength of 780 nm based on a MOCVD-grown Al x Ga1–x As/Al y Ga1–y As heterostructure with optical and electron beam pumping

A pulsed semiconductor disk laser based on the Al x Ga1 – x As/Al y Ga1 – y As structure with resonantly periodic gain and a built-in Bragg mirror emitting at a wavelength near 780 nm is studied. The laser characteristics are presented both for pumping by an electron beam and for optical pumping by laser diode radiation with a wavelength of 450 nm. Under pumping by an electron beam, a peak power of 4.4 W is achieved with a slope efficiency of over 10 %, while under optical pumping, the power is 0.2 W with a slope efficiency of 2.2 % and approximately the same cavity parameters. Possible reasons for the lower powers and efficiency under optical pumping are discussed.

Vertical stacks of pulsed (100 ns) mesa-stripe semiconductor lasers with an ultra-wide (800 μm) aperture emitting kilowatt-level peak power at a wavelength of 1060 nm

A pulsed source of radiation in the spectral region of 1060 nm with a kilowatt level peak output power is developed based on a vertical stack of microbars of stripe semiconductor lasers with an ultra-wide (800 μm) aperture. The laser stack contains three microbars with three emitters each, which ensures an emitting area of 2.6 × 0.4 mm. The highest radiative efficiency of the stack is 2.48 W A−1. The maximum achieved peak power reached 1400 W under pumping by current pulses with an amplitude of 650 A and a duration of 100 ns and is limited by the current source capacity.

Controlling exciton spontaneous emission of quantum dots by Au nanoparticles

As an ideal single-photon source, quantum dots (QDs) can play a unique role in the field of quantum information. Controlling QD exciton spontaneous emission can be achieved by anti-phase coupling between QD exciton dipole field and Au dipole field after QD film has been transferred onto the Si substrate covered by Au nanoparticles. In experiment, the studied InAs/GaAs QDs are grown by molecular beam epitaxy (MBE) on a (001) semi-insulation substrate. The films containing QDs with different GaAs thickness values are separated from the GaAs substrate by etching away the AlAs sacrificial layer and transferring the QD film to the silicon wafer covered by Au nanoparticles with a diameter of 50 nm. The distance <i>D</i> (thickness of GaAs) from the surface of the Au nanoparticles to the QD layer is 10, 15, 19, 25, and 35 nm, separately. A 640-nm pulsed semiconductor laser with a 40-ps pulse length is used to excite the QD samples for measuring QD exciton photoluminescence and time-resolved photoluminescence spectra at 5 K. It is found that when the distance <i>D</i> is 15–35 nm the spontaneous emission rate of exciton is suppressed. And when <i>D</i> is close to 19 nm, the QD spontaneous emission rate decreases to <inline-formula><tex-math id="M2">\begin{document}$ ~{10}^{-3} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20211863_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20211863_M2.png"/></alternatives></inline-formula>, which is consistent with the theoretical calculations. The physical mechanism of long-lived exciton luminescence observed in experiment lies in the fact that Au nanoparticles scatter the light field of the exciton radiation in the QD wetting layer, and the phase of the scattered field is opposite to the phase of the exciton radiation field. Therefore, the destructive interference between the exciton radiation field and scattering field of Au nanoparticles results in long-lived exciton emission observed in experiment.

Observation of frequency dependent resonances in magnetic vortex core gyration using time-resolved magneto-optical Kerr microscope with pulsed semiconductor laser illumination

Frequency dependent resonance of magnetic vortex core gyration in micrometer sized permalloy squares was observed by time-resolved magneto-optical Kerr microscope using pulsed semiconductor lasers as a light source in the stroboscopic method. Uniform and efficient laser illumination was realized by a speckle reducer consisting of an oscillating multimode optical fiber and a microbending mode scrambler. The resonance frequency of the same sized permalloy squares showed a non-uniformity of up to 15%, suggesting the flatness of the underlayer has a strong influence on the gyration motion.

Laser requirements for the designof fast laser-driven semiconductor switches for THz and mm-waves.

A reduced parameter model of fast laser-driven semiconductor switches of THz and mm-waves has been developed. The model predicts peak reflectivity and minimum transmissivity of switches, showing good agreement with experimental data, while requiring fewer inputs than published models. This simplification facilitated a systematic survey of laser parameters required for efficient switching. Laser energy density requirements are presented as a function of laser wavelength, laser pulse width, switched frequency, reflection angle, and semiconductor material (silicon or gallium arsenide). Analytical expressions have been derived to explain the dependence of laser requirements on switch parameters and to derive practical minima of required laser energy density. Diffusion is shown to quickly negate the shallow absorption advantage of laser wavelengths shorter than about 500nm in silicon or 800nm in gallium arsenide. Decreasing laser pulse width, to a derived limit, and switching S-polarized THz or mm-wave signals are shown to be means of lowering required laser energy. This is an especially useful result for devices operating at high power levels or THz frequencies, where extended switches are used in quasioptical systems.

High-power pulsed hybrid semiconductor lasers emitting in the wavelength range 900–920 nm

High-power hybrid semiconductor lasers–thyristors (λ=900−920nm) consisting of thyristor crystals soldered in series with an integrated semiconductor laser with three emitting sections are studied. A monolithic laser–thyristor with three emitting sections is used as a reference sample. The output power of the triple monolithically integrated laser–thyristor is ∼120 W at a turn-on voltage of 18 V. The turn-on voltage of a hybrid laser–thyristor with three emitting sections is 28 V, and the peak output power reaches ∼170 W.

>25 W pulses from 1.5 μm double‐asymmetric waveguide, 100 μm stripe laser diode with bulk active layer

The experimental characterization of a high-power pulsed semiconductor laser operating in the eye-safe spectral range (wavelength around 1.5 μm), with an asymmetric waveguide structure, a 100 μm wide stripe, and a bulk active layer positioned very close to the p-cladding, is reported. An anti-reflection/high reflection coated laser with a stripe width of 100 μm exhibits a single-facet output power over 25 W at a pumping current amplitude of 100 A.

Selection of laser pulse width for efficient generation of photoacoustic signals in liquid-filled thin capillary embedded in soft material

To design an instrumentation system for evaluating contrast agents of photoacoustic imaging, the optimal pulse width of the excitation laser is discussed in this paper. A pulsed semiconductor laser with a moderate pulse width (15–129 ns) and low peak power (1 W) is adopted in the proposed system. Black ink is selected as the reference sample, which is filled in a glass capillary embedded in a soft phantom. Our aim is that the pulse width matches the acoustic resonance of the target and the center frequency of the receiving transducer (5 MHz) to obtain sufficient strength of the ultrasonic signal with minimal laser power. A series of experiments reveal a clear relationship between the laser pulse width and the maximal amplitude of the resonance mode. Acoustic resonance occurs inside the capillary whose frequencies can be precisely predicted as the radial eigen mode. The laser pulse width and concentration of the sample showed little influence on these resonance frequencies as expected. To efficiently utilize the signal enhancement effect due to the resonance, several resonance mode candidates are investigated and discussed. It then becomes clear that the second angular and zeroth radial order mode is useful for capillaries with sub-millimeter inner diameters. It was demonstrated that the concentration of samples had very limited influence on the frequencies. Finally, consideration based on two delayed attenuating vibrations is successfully conducted to explain the experimental results.

Isolated Soft Switching Current Fed Series LC Resonant DC-DC Convertor for Electrical Vehicle Application

The current fed series resonant converter for electrical vehicle application is offered in this paper. The converter is able to achieve ZVS for primary side semiconductor switches. In the overlap time of voltage and current at zero crossing series resonant tank circuit is gives short interval of resonant pulse. This resonant pulse provide natural voltage decrease for semiconductor switches and voltage pulse is zero earlier compare to current across switches and ZVS achieve for semiconductor switches. All devices turn off softly so dependency on snubber is decreased to clamp the voltage across the switches. Presented converter reduce the circulating current so switching losses is decreased and converter efficiency will improvise. The proposed converter is simulated in MATLAB Simulink environment to investigate and analyses the proposed converter.

Light – current characteristics of high-power pulsed semiconductor lasers (1060 nm) operating at increased (up to 90 °C) temperatures

Pulsed radiative characteristics of high-power semiconductor lasers based on an asymmetric InGaAs/AlGaAs/GaAs heterostructure with an active region including two quantum wells and a gradient waveguide on the side of the p-emitter are studied. It is shown that the use of the proposed design allows efficient laser operation under pumping by 100-ns current pulses in the temperature range 25 – 90 °C. The lasers with a Fabry – Perot cavity 2900 μm long demonstrated peak powers of 62 W (injection current 123 A) and 43 W (122 A) at temperatures of 25 and 90 °C, respectively. It is found that at room temperature and currents of ∼50A, a decrease in the cavity length to 600 μm does not cause a decrease in the output power with respect to the power of lasers with a long (2900 μm) cavity. An increase in temperature to 90 °C at high injection currents leads to a sharp decrease in the radiative efficiency of lasers with a short (600 μm) cavity and to the change of their operation regime to the two-band lasing.