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1
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Exciton Binding Energy and Oscillator Strength in a Shallow Quantum Well in an External Magnetic Field

100%
Zięba P., Piętka B., Łusakowski J., Tralle I.
Acta Physica Polonica A
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2015
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vol. 128
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issue 2
237-239
EN
We discuss the influence of an external magnetic field on the exciton energy and the exciton oscillator strength in the shallow quantum wells. We include into consideration the Coulomb attraction between electron and hole, which is rarely taken into account. We self-consistently solve the Schrödinger equation to compare the obtained results with the experimental values.
2
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Magnetic Field Effect on the Excitation Spectrum of a Neutral Exciton in a Single Quantum Dot

88%
Molas M., Nicolet A., Piętka B., Babiński A., Potemski M.
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vol. 126
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issue 5
1066-1068
EN
Excitation-energy-dependent magnetospectroscopic measurements of a single GaAlAs/AlAs quantum dot were performed. A significant effect of the excitation energy on the photoluminescence spectra is reported. The photoluminescence excitation spectroscopy has been used to investigate the excitation spectrum of a single electron-hole pair - a neutral exciton in magnetic field up to 14 T. The observed resonances exhibit diamagnetic shift characteristic of an s-shell related emission. In our opinion, the creation of excited complexes involving an excited hole and a ground electron is responsible for the process.
3
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Fine Structure of Neutral Excitons in Single GaAlAs Quantum Dots

88%
Molas M., Gołasa K., Piętka B., Potemski M., Babiński A.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
988-990
EN
Optical anisotropy of neutral excitons in GaAlAs/AlAs quantum dots is investigated. Low-temperature polarization-sensitive photoluminescence measurements of single quantum dots are performed. It is found that neutral excitons (X) in the quantum dots exhibit a fine structure splitting. The fine structure splitting ranges from 10 μeV to 100 μeV and correlates with the X energy. The polarization axis of the fine structure splitting is well oriented along [110] crystallographic direction of a substrate. The orientation is attributed to the elongation of GaAlAs/AlAs quantum dots in the [110] direction of the substrate.
4
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Resonant Plasmon Response of a Periodically Modulated Two-Dimensional Electron Gas

88%
Sznajder P., Piętka B., Szczytko J., Łusakowski J., Bardyszewski W.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1090-1092
EN
We report the theoretical study of the optical response of a periodically modulated two-dimensional electron gas. The density of states is calculated within the first order of the perturbation theory and the effects of the short-range disorder are explained and discussed. We demonstrate that the magnetic field values corresponding to the characteristic narrowing of the density of states width are given by the zeros of the subsequent Laguerre polynomials. The observed increase of the density of states at the edges are interpreted as van Hove singularities. The broadening effects are shown to modify and smear out the observed effects with increasing temperature above 2 K. The plasmon dispersion relation is discussed in terms of the random phase approximation. Small changes in plasmon dispersion relation related to the periodic modulation were predicted.
5
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Confocal Microscope Studies of MoS_{2} Layer Thickness

88%
Grzeszczyk M., Gołasa K., Piętka B., Babiński A., Szczytko J.
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vol. 126
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issue 5
1207-1208
EN
We have been studying micro-luminescence of various exfoliated MoS_{2} flakes using a confocal microscope. A crucial issue is to determine thickness of the investigated layer. The common way - using atomic force microscopy, electron microscopy or the Raman spectroscopy - requires moving the sample out from the confocal microscope experimental setup and looking for a particular exfoliated flake hidden among thousands of others. In order to preliminarily determine thickness of investigated layers we have performed a study on optical reflectivity and compared the results with the Raman spectroscopy investigations. In this way we were able to calibrate our experimental setup. Optical measurements are much faster than the Raman spectroscopy and can give a good estimation of MoS_{2} thickness.
6
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Magnetic Field Induced Redistribution of Exciton-Polariton Density on Confined Modes

76%
Piętka B., Szczytko J., Łusakowski J., Nardin G., Léger Y., Morier-Genoud F., Deveaud-Plédran B.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1093-1095
EN
The influence of magnetic field on confined exciton-polariton modes inside a semiconductor microcavity is discussed. The three-dimensional confinement for exciton-polaritons is achieved by the mesa structures confining the photonic part of polaritons. We observe a strong increase of the polariton emission intensity and we argue that this effect is due to the change of the oscillator strength of the excitonic component of polaritons and the change of the excitonic content in polariton state as the magnetic field increases.
7
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Relative Reflection Difference as a Method for Measuring the Thickness of the Exfoliated MoSe₂ Layers

64%
Łempicka K., Norowski K., Grzeszczyk M., Król M., Lekenta K., Babiński A., Piętka B., Szczytko J.
Acta Physica Polonica A
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2017
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vol. 132
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issue 2
316-318
EN
We propose a method for measuring the thickness of the exfoliated MoSe₂ layers deposited on Si/SiO₂ substrate, based on the reflectance measurements performed with laser light illumination at two different wavelengths: red and green from confocal microscope at room temperature. We demonstrate the correlation between the number of layers in a flake and the value of its relative reflection difference. We applied the transfer matrix method to calculate the reflectivity and verify our experimental results. The approach proposed by us allows for fast and automatic verification of the exfoliated MoSe₂ layers thickness on large areas of the substrate.
8
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THz Time Domain Spectroscopy of Thin Gold Layers on GaAs

64%
Szczytko J., Adomavicius R., Papis E., Barańska A., Wawro A., Krotkus A., Piętka B., Łusakowski J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1118-1120
EN
Thin layers of Au with the thickness of several nanometers were prepared on a semi-insulating GaAs substrate. The layers' thickness was determined by ellipsometry. THz time-domain spectroscopy was applied to determine a complex index of refraction of thin Au layers. The obtained results allow for a more precise modeling of the performance of semiconductor devices at THz frequencies.
9
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Magnetoplasmons in a High Electron Mobility GaAs/AlGaAs Heterostructure

64%
Białek M., Karpierz K., Piętka B., Grynberg M., Łusakowski J., Czapkiewicz M., Fronc K., Wróbel J., Umansky V.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1096-1098
EN
We have observed a multimode spectrum of magnetoplasmons in the Hall bars processed on a high electron mobility GaAs/AlGaAs heterostructure. We have found that the dispersion relation of these excitation follows square root dependence. Calculated wavelength of the fundamental magnetoplasmon mode fits to the width of sample.
10
Content available remote

Control of Photon Polarization in GaAs/AlAs Single Quantum Dot Emission

52%
Suffczyński J., Trajnerowicz A., Kazimierczuk T., Piętka B., Kowalik K., Kossacki P., Golnik A., Nawrocki M., Gaj J., Wysmołek A., Stępniewski R., Potemski M., Thierry-Mieg V.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
461-466
EN
We study polarization resolved correlation between photons emitted in cascaded biexciton-exciton recombination from a single quantum dot formed in type II GaAs/AlAs bilayer. Magnetic field induced transition from anisotropy controlled to the Zeeman controlled emission was demonstrated by a circular polarization correlation between the emitted photons. A simple model describing the effect allowed us to determine the anisotropic exchange splitting of the excitonic state. This method of the anisotropic exchange splitting determination can be useful in the case when other methods are not sensitive enough.
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