Photon echo from trions in semiconductor quantum wells and quantum dots

The present work is dedicated to the study of the ultrafast coherent dynamics of the excitonic complexes localized in semiconductor nanostructures. We consider the optical control of the optical and spin coherence of the negatively charged excitons using the photon echo technique. In the first two chapters, we overview the basic knowledge of the research area and the experimental techniques. In the third chapter, we considered the freezing of the dephasing in the inhomogeneously broadened ensembles of InGaAs quantum dots driven by the application of a resonant control pulse with an area of multiple of 2p. The freezing of dephasing allows us to vary the timing of the photon echo by up to 5 ps, which even slightly exceeds the echo duration. In the fourth chapter, we consider the resident electron dynamics in the CdTe quantum well. Long-lived three-pulse photon echoes in combination with the pump-probe Kerr rotation allowed us to analyze comprehensively the resident electron dynamics since they are differently impacted by the hopping of the resident electrons between the different localization sites. From the data, we evaluate the hopping rate all-optically. In the fifth chapter, we demonstrate the long-lived three-pulse photon echoes from the ensembles of the InGaAs quantum dots. It allowed us to extend the coherent optical response by at least an order of magnitude. We show that the transverse g-factor of the heavy hole in the trion state strongly impacts the temporal evolution of the system, and therefore modifies the long-lived three-pulse photon echo signal.Die vorliegende Arbeit widmet sich der Untersuchung der ultraschnellen Dynamik exzitonischer Komplexe, die in Halbleiter-Nanostrukturen lokalisiert sind. Wir betrachten die optische Kontrolle der optischen und Spinkohärenz der negativ geladenen Exzitonen unter Verwendung der Photonenechotechnik. In den ersten beiden Kapiteln geben wir einen Überblick über das Grundwissen zum Forschungsgebiet und den Versuchstechniken. Im dritten Kapitel betrachteten wir das Einfrieren der Dephasierung in den inhomogen verbreiterten Ensembles von InGaAs-Quantenpunkten, angetrieben durch das Anlegen eines resonanten Steuerpulses mit einer Fläche von einem Vielfachen von 2p. Durch das Einfrieren können wir das zeitliche Maximum des Photonenechos um bis zu 5 ps variieren, was die Echodauer sogar geringfügig überschreitet. Im vierten Kapitel betrachten wir die Dynamik von residenten Elektronen im CdTe-Quantentopf. Langlebige Dreipuls-Photonenechos in Kombination mit der Pump-Probe-Kerr-Rotation ermöglichten uns eine umfassende Analyse der Dynamik von residenten Elektronen, da sie durch das Springen der residenten Elektronen zwischen den verschiedenen Lokalisationsorten unterschiedlich beeinflusst wird. Aus den Daten werten wir optisch die Hopping-Rate aus. Im fünften Kapitel demonstrieren wir die langlebigen Dreipuls-Photonenechos von InGaAs-Quantenpunkt Ensemblen. Es erlaubte uns, die kohärente optische Antwort um mindestens eine Grössenordnung zeitlich zu erweitern. Wir zeigen, dass der transversale g-Faktor des schweren Lochs im Trion-Zustand die zeitliche Entwicklung des Systems stark beeinflusst und daher das langlebige Dreipuls-Photonenechosignal modifiziert

МЕТОДИ ОЧИЩЕННЯ ГАЗОВИХ ВИКИДІВ ВІД ХІМІЧНО-НЕБЕЗПЕЧНИХ РЕЧОВИН ДЛЯ ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ФІЛЬТРУВАЛЬНИХ СИСТЕМ

A wide variety of sources of emission of harmful substances into the atmosphere, differing in nature and concentration of harmful substances, temperature, pressure, periodicity and duration of release, the presence of associated impurities in the exhaust gases determine the choice of a rational method and equipment for gas purification. In the arsenal of air pollution protection techniques, there are numerous absorption, adsorption, catalytic, thermal and other methods of gas purification. The methods of purification of gaseous emissions depending on the physical and chemical properties of pollutants, in particular chemical-dangerous, their aggregate state, concentration in the gas environment are considered. The influence of aerosol content such as dust and soot; the efficiency of cleaning methods at different temperature intervals, methods of cleaning multicomponent mixtures. The comparative characteristics of thermochemical, reagent, sorption and catalytic methods are given and the prospects of their application in the filter systems of stationary and mobile objects are estimated.Рассмотрены методы очистки газообразных выбросов в зависимости от физико-химических свойств загрязняющих веществ, в том числе химически опасных, их агрегатного состояния, концентрации в газовой среде. Проанализировано влияние содержания аэрозолей, таких как пыль и сажа; работоспособность методов очистки в различных температурных интервалах, способы очистки многокомпонентных смесей. Приведена сравнительная характеристика термохимических, реагентных, сорбционных и каталитических методов и оценены перспективы их применения в фильтровальных системах стационарных и мобильных объектов.Розглянуто методи очищення газоподібних викидів залежно від фізико-хімічних властивостей забруднювальних речовин, зокрема хімічно-небезпечних, їх агрегатного стану, концентрації в газовому середовищі. Проаналізовано вплив вмісту аерозолів, таких як пил і сажа; працездатність методів очищення в різних температурних інтервалах, способи очищення багатокомпонентних сумішей. Наведено порівняльну характеристику термохімічних, реагентних, сорбційних і каталітичних методів та оцінено перспективи їх застосування в фільтрувальних системах стаціонарних і мобільних об’єктів

Mentoring as a Predominant Factor Affecting Well-Being of Older People

The authors of the paper studied the state of well-being of older people who retired and stop working at the company they have worked for over 20 years. The survey provided some useful insights into the problem with the reference to three samples of 10 older people from each group: 1) older people who retired and keep in touch with the previous organisation; 2) older people who retired and continue working at the company as consultants, supervisors, experts, mentors etc.; 3) older people who retired and work in another enterprise and lost the touch with the previous organisation. Retired people took part in present research by completing a questionnaire survey. A set of data was examined by being compared to reveal the state of older people’s well-being criteria predominance in the various sample groups

Accurate photon echo timing by optical freezing of exciton dephasing and rephasing in quantum dots

Semiconductor quantum dots are excellent candidates for ultrafast coherent manipulation of qubits by laser pulses on picosecond timescales or even faster. In inhomogeneous ensembles a macroscopic optical polarization decays rapidly due to dephasing, which, however, is reversible in photon echoes carrying complete information about the coherent ensemble dynamics. Control of the echo emission time is mandatory for applications. Here, we propose a concept to reach this goal. In a two-pulse photon echo sequence, we apply an additional resonant control pulse with multiple of 2π area. Depending on its arrival time, the control slows down dephasing or rephasing of the exciton ensemble during its action. We demonstrate for self-assembled (In,Ga)As quantum dots that the photon echo emission time can be retarded or advanced by up to 5 ps relative to its nominal appearance time without control. This versatile protocol may be used to obtain significantly longer temporal shifts for suitably tailored control pulses

Operational experience of GNSS receivers with Chip Scale Atomic Clocks for baseline measurements

Currently, one of the topical issues of improving GLONASS system is modernization of its uniformity measurement equipment, including RF measurement equipment and electronic length measurement equipment. To this end, at the Spatial Reference Proving Ground of theSiberian State University of Geosystems and Technologies (SSUGT), the authors of this article carried out a successful experiment to measure a short GNSS baseline by receivers equipped with Chip Scale Atomic Clocks (CSACs) with instability of 10−11 showed that the mean deviation between the slant distance (D) measured using GNSS receivers connected to CSACs and their certified value varied in the range of 0.1–2.5 mm, with the average value of 0.9 mm. The mean deviation obtained using GNSS geodetic receivers not connected to CSAC and their certified value made up 9.4 mm. The obtained experimental results suggest that substitution of quartz frequency generators with temperature compensation used in geodetic GNSS receivers for Chip Scale Atomic Clocks in any metrological or verification kit increases accuracy and reliability of short baselines measurements results, which highly perspective in view of development of techniques for creating reference baselines with a reproduction error of unit length of about 1 mm per 1 km. The above-mentioned experiment opens up new horizons for the use of Chip Scale Atomic Clocks in such fields of science as metrological support of geodetic equipment, geodesy, etc

Extending the time of coherent optical response in ensemble of singly-charged InGaAs quantum dots

The ability to extend the time scale of the coherent optical response from large ensembles of quantum emitters is highly appealing for applications in quantum information devices. In semiconductor nanostructures, spin degrees of freedom can be used as auxiliary, powerful tools to modify the coherent optical dynamics. Here, we apply this approach to negatively charged (In,Ga)As/GaAs self-assembled quantum dots which are considered as excellent quantum emitters with robust optical coherence and high bandwidth. We study three-pulse spin-dependent photon echoes subject to moderate transverse magnetic fields up to 1 T. We demonstrate that the timescale of coherent optical response can be extended by at least an order of magnitude by the field. Without magnetic field, the photon echo decays with T2 = 0.45 ns which is determined by the radiative lifetime of trions T1 = 0.26 ns. In the presence of the transverse magnetic field, the decay of the photon echo signal is given by spin dephasing time of the ensemble of resident electrons T2,e ∼ 4 ns. We demonstrate that the non-zero transverse g-factor of the heavy holes in the trion state plays a crucial role in the temporal evolution and magnetic field dependence of the long-lived photon echo signal

'Limosilactobacillus fermentum' Strain 3872 : antibacterial and immunoregulatory properties and synergy with prebiotics against socially significant antibiotic-resistant infections of animals and humans

Limosilactobacillus fermentum strain 3872 (LF3872) was originally isolated from the breast milk of a healthy woman during lactation and the breastfeeding of a child. The high-quality genome sequencing of LF3872 was performed, and a gene encoding a unique bacteriocin was discovered. It was established that the bacteriocin produced by LF3872 (BLF3872) belongs to the family of cell-wall-degrading proteins that cause cell lysis. The antibacterial properties of LF3872 were studied using test cultures of antibiotic-resistant Gram-positive and Gram-negative pathogens. Gram-positive pathogens (Staphylococcus aureus strain 8325-4 and S. aureus strain IIE CI-SA 1246) were highly sensitive to the bacteriolytic action of LF3872. Gram-negative pathogens (Escherichia coli, Salmonella strains, and Campylobacter jejuni strains) were more resistant to the bacteriolytic action of LF3872 compared to Gram-positive pathogens. LF3872 is a strong co-aggregator of Gram-negative pathogens. The cell-free culture supernatant of LF3872 (CSLF3872) induced cell damage in the Gram-positive and Gram-negative test cultures and ATP leakage. In the in vitro experiments, it was found that LF3872 and Actigen prebiotic (Alltech Inc., Nicholasville, KY, USA) exhibited synergistic anti-adhesive activity against Gram-negative pathogens. LF3872 has immunoregulatory properties: it inhibited the lipopolysaccharide-induced production of proinflammatory cytokines IL-8, IL-1β, and TNF-α in a monolayer of Caco-2 cells; inhibited the production of IL-12 and stimulated the production of IL-10 in immature human dendritic cells; and stimulated the production of TGF-β, IFN-γ, and IgA in the immunocompetent cells of intestinal Peyer’s patches (PPs) in mice. These results indicate the possibility of creating a synbiotic based on LF3872 and a prebiotic derived from Saccharomyces cerevisiae cell wall components. Such innovative drugs and biologically active additives are necessary for the implementation of a strategy to reduce the spread of antibiotic-resistant strains of socially significant animal and human infections

Design, Performance, and Calibration of CMS Hadron Endcap Calorimeters

Detailed measurements have been made with the CMS hadron calorimeter endcaps (HE) in response to beams of muons, electrons, and pions. Readout of HE with custom electronics and hybrid photodiodes (HPDs) shows no change of performance compared to readout with commercial electronics and photomultipliers. When combined with lead-tungstenate crystals, an energy resolution of 8\% is achieved with 300 GeV/c pions. A laser calibration system is used to set the timing and monitor operation of the complete electronics chain. Data taken with radioactive sources in comparison with test beam pions provides an absolute initial calibration of HE to approximately 4\% to 5\%

Synchronization and Timing in CMS HCAL

The synchronization and timing of the hadron calorimeter (HCAL) for the Compact Muon Solenoid has been extensively studied with test beams at CERN during the period 2003-4, including runs with 40 MHz structured beam. The relative phases of the signals from different calorimeter segments are timed to 1 ns accuracy using a laser and equalized using programmable delay settings in the front-end electronics. The beam was used to verify the timing and to map out the entire range of pulse shapes over the 25 ns interval between beam crossings. These data were used to make detailed measurements of energy-dependent time slewing effects and to tune the electronics for optimal performance