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Tytuł:
Badanie procesu nasiąkania struktur porowatych
Investigation on imbibition of porous structures
Autorzy:
Sęk, J.
Tryluk, M.
Kucharek, A.
Powiązania:
https://bibliotekanauki.pl/articles/2070553.pdf
Data publikacji:
2009
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
ciała porowate
nasiąkanie
równanie Washburna
porous media
imbibition
Washburn equation
Opis:
Podjęto próbę zaproponowania zależności, które pozwalałyby z większą dokładnością niż powszechnie stosowane równanie Washbuna przewidywać przebieg procesu nasiąkania materiałów porowatych. Zaproponowano wykorzystanie czterech takich równań sprawdzając ich przydatność w oparciu o własne dane doświadczalne.
An attempt was carried out to provide dependences that would allow one to predict a course of imbibition processes with higher accuracy then the commonly used Was/t6HrM equation. Four such formulae were proposed and yerified using own experimental data.
Źródło:
Inżynieria i Aparatura Chemiczna; 2009, 4; 112-113
0368-0827
Pojawia się w:
Inżynieria i Aparatura Chemiczna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Badanie procesu przesiąkania roztworów olejów roślinnych i substancji ropopochodnych przez ośrodek porowaty
Investigation of the percolation of the solutions of vegetable oils and crude oil derivatives through porous bed
Autorzy:
Sęk, J.
Dziubiński, M.
Błaszczyk, M.
Padyk, A.
Powiązania:
https://bibliotekanauki.pl/articles/401223.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Inżynierii Ekologicznej
Tematy:
przesiąkanie
złoża porowate
zanieczyszczenie gleb
turbidymetria
percolation
porous bed
turbidymetry
Opis:
Ropa naftowa i jej pochodne stanowią jedno z ważniejszych źródeł zanieczyszczeń gruntów i wód gruntowych. Postępująca industrializacja oraz rozwój motoryzacji są przyczyną większego zapotrzebowania na produkty naftowe. Wzrost wydobycia, przetwórstwa i zużycia ropy naftowej nieuchronnie pociąga za sobą zwiększenie przypadków zanieczyszczenia środowiska związkami ropopochodnymi. W pracy tej przedstawione zostały badania przesiąkania cieczy o różnych właściwościach fizykochemicznych przez warstwy ziarniste w warunkach nieustalonych. Podjęta została próba opisu zjawiska przesiąkania płynów modelowych za pomocą równań matematycznych uwzględniających wpływ lepkości cieczy na przebieg tego procesu. Podjęto także próbę oszacowania łatwości wymywania związków ropopochodnych z warstwy ziarnistej za pomocą wody.
Crude oil and its derivatives are one of the major sources of pollution of land and groundwater. Increasing industrialization and development of automotive industry are causing a greater demand for oil products. The increase in mining, processing and consumption of oil will inevitably entail an increase in cases of environmental pollution with these compounds. In this work were presented penetration research liquids with different physical and chemical properties of granular layer in transients term. Attempt is made to describe the phenomenon of percolation fluid models using mathematical equations taking into account the effect of viscosity on this process. An attempt to estimate the ease of leaching of petroleum compounds from the granular layer by water. The aim of this study was to determine the efficiency of migration processes of high-viscosity substance in the soil.
Źródło:
Inżynieria Ekologiczna; 2011, 26; 48-58
2081-139X
2392-0629
Pojawia się w:
Inżynieria Ekologiczna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Badanie procesu przesiąkania wody przez warstwy ziarniste w warunkach nieustalonych
Non-steady water percolation into granular beds
Autorzy:
Sęk, J.
Stopczyk, A.
Browarski, T.
Powiązania:
https://bibliotekanauki.pl/articles/2070939.pdf
Data publikacji:
2010
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
warstwa ziarnista
przesiąkanie wody
opory przepływu
granular beds
percolation
flow resistance
Opis:
Przeprowadzono badania procesu przesiąkania wody w warunkach nieustalonych przez warstwy ziarniste o różnej granulacji i różnej zawartości początkowej wilgoci. Wykazano, że proces ten może być podzielony na dwa etapy. W czasie pierwszego z nich zachodzi saturacja warstwy porowatej, a przebieg tego zjawiska ma charakter liniowy. Zaproponowany opis matematyczny pozwalający wyznaczyć prędkość wsiąkania w warstwę nieza-wierającą wilgoci. Przebieg drugiego etapu opisano za pomocą zależności potęgowej wprowadzając pojęcie współczynnika oporów przepływu, korzystając przy tym z zasad opisujących przebieg zjawisk grawitacyjnego wypływu cieczy ze zbiornika
Investigations concerning the non-steady water percolation into granular beds were performed. Two process stages were distinguished. In the first one rising saturation of the bed occurred and it can be described using linear equations. The applied procedure aHowed one to determine the percolation velocity in beds during a dry state. The second process stage was described using the approach typical for gravitational flow from a tank. A concept of flow resistance coefficient was introduced.
Źródło:
Inżynieria i Aparatura Chemiczna; 2010, 2; 111-112
0368-0827
Pojawia się w:
Inżynieria i Aparatura Chemiczna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Binaural masking of amplitude modulation
Autorzy:
Kordus, M.
Sęk, A.
Kociński, J.
Powiązania:
https://bibliotekanauki.pl/articles/177557.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
masking
masking in the modulation domain
modulation filterbank
Opis:
A new concept concerned with the transformation of acoustic stimuli in the auditory system postulates the existence of a form of spectral analysis applied to the amplitude changes of the stimuli. It is assumed that this analysis takes place in the so-called modulation filters, i.e. bandpass linear filters tuned to different rates of the amplitude changes. The most striking argument supporting this idea is an effect of masking in the amplitude modulation domain whose nature can be easily explained basing on this concept. As the modulation filters are situated on the higher levels of the auditory system, it is also assumed that this form of masking is entirely a central process. However, most of the studies concerned with masking in the modulation domain used monaural listening only. Therefore, the main purpose of the presented here experiments was to investigate whether this type of masking is entirely a central process. Using a Three-Alternative Forced-Choice (3AFC) procedure the binaural and monaural masked thresholds of amplitude modulation were determined. A sinusoidal carrier at a frequency of 4 kHz was amplitude modulated by a specially designed band of noise characterized by a very low value of the crest factor, which was used as a masking signals. Different bandwidths of the modulating masking signals were used as well as different center frequencies to investigate whether the masking patterns in the modulation domain depend on the masker bandwidth and its center frequency. The modulating target (masked) signal was a pure tone at a frequency range from 2 to 256 Hz. Both modulating signals were applied to the same sinusoidal carrier signal. The most effective masking was noticed when the rate of the sinusoidal modulation was close to the center frequency of the masking signal or when it was in its spectral range and decreased outside of this range. The character of this dependence confirms the existence of some form of a frequency selectivity in the modulation rate domain similarly to the audible frequency domain. The thresholds for monaural and binaural listening were very close to each other. This implies that masking in the modulation domain is a central process.
Źródło:
Archives of Acoustics; 2005, 30, 1; 5-17
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Convolutive Blind Signal Separation Spatial Effectiveness in Speech Intelligibility Improvement
Autorzy:
Kociński, J.
Sęk, A.
Libiszewski, P.
Powiązania:
https://bibliotekanauki.pl/articles/1504381.pdf
Data publikacji:
2011-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.72.-p
43.60.-c
43.60.+d
Opis:
Blind signal separation is one of the latest methods to improve the signal to noise ratio. The main objective of blind source separation is the transformation of mixtures of recorded signals to obtain each source signal at the output of the procedure, assuming that they are statistically independent. For acoustic signals it can be concluded that the correct separation is possible only if the source signals are spatially separated. That finding suggests analogies with the classical spatial filtering (beamforming). In this study we analyzed an effect of the angular separation of two source signals (i.e. speech and babble noise) to improve speech intelligibility. For this purpose, we chose the blind source separation algorithm based on the convolutive separation, based on second order statistics only. As a system of sensors a dummy head was used (one microphone inside each ear canal), which simulated two hearing aids of a hearing impaired person. The speech reception threshold, before and after the blind source separation was determined. The results have shown significant improvement in speech intelligibility after applying blind source separation (speach reception threshold fell even more than a dozen dB) in cases where the source signals were angularly separated. However, in cases where the source signals were coming from the same directions, the improvement was not observed. Moreover, the effectiveness of the blind source separation, to a large extent, depended on the relative positions of signal sources in space.
Źródło:
Acta Physica Polonica A; 2011, 119, 6A; 996-999
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Doctor Honoris Causa of the Adam Mickiewicz University for Professor Brian C. J. Moore
Doktor Honoris Causa Uniwersytetu Adama Mickiewicza dla prof. Briana C. J. Moore’a
Autorzy:
Sęk, A.
Powiązania:
https://bibliotekanauki.pl/articles/177129.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Brian Cecil Joseph Moore
Opis:
On November 9th, a.d. 2015, Professor Brian Cecil Joseph Moore from Cambridge University (UK), received the title of Doctor Honoris Causa of Adam Mickiewicz University from the hands of His Magnificence, the Rector of the AMU. Professor Brian Moore is a great scholar with a broad, in-depth knowledge and extremely wide research interests in many areas that go far beyond the mainstream of his research. He is a physicist, an acoustician and a psychologist.
Źródło:
Archives of Acoustics; 2016, 41, 2; 351-354
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Confinement Anisotropy on Excitonic Properties in InAs/InP Quantum Dashes
Autorzy:
Mrowiński, P.
Musiał, A.
Sęk, G.
Misiewicz, J.
Höfling, S.
Somers, A.
Hein, S.
Forchel, A.
Powiązania:
https://bibliotekanauki.pl/articles/1399087.pdf
Data publikacji:
2013-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.35.-y
71.70.Gm
78.67.Hc
73.21.-b
81.07.Ta
Opis:
The influence of confinement potential anisotropy on emission properties of strongly elongated single InAs/InGaAlAs/InP quantum dashes has been investigated by polarization-resolved microphotoluminescence spectroscopy at around 1.5 μm. There have been determined the exciton fine structure splitting, degree of linear polarization of surface emission and biexciton binding energy. The investigated dashes exhibited usually: the exciton anisotropy splitting larger than 100 μeV, the corresponding biexciton binding energy of about 3 meV, and the degree of linear polarization values in the range from 24% to 55%. Here, we presented a correlation of these parameters for several quantum dashes, which can be attributed either to a change in lateral aspect ratio within the ensemble, or the carrier localization on random fluctuations of the dash confinement potential.
Źródło:
Acta Physica Polonica A; 2013, 124, 5; 801-804
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of dielectric medium anisotropy on the polarization degree of emission from a single quantum dash
Autorzy:
Mrowiński, P.
Tarnowski, K.
Olszewski, J.
Somers, A.
Kamp, M.
Höfling, S.
Reithmaier, J.
Urbańczyk, W.
Misiewicz, J.
Machnikowski, P.
Sęk, G.
Powiązania:
https://bibliotekanauki.pl/articles/1159588.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
71.35.-y
78.55.-m
Opis:
Excitonic emission from single InAs/InGaAlAs/InP quantum dashes has been investigated in the context of degree of linear polarization by post-growth modification of its surrounding dielectric medium. We present optical spectroscopy measurements on a symmetric squared pedestal structures (mesas), and asymmetric rectangular ones oriented parallel or perpendicular to the main in-plane axis of the dashes [1-10]. Polarization resolved microphotoluminescence shows a significant quantitative modification of the degree of linear polarization value from -20% up to 70%. These results have been confronted with calculations of the coupling between the exciton transition dipole moment and electromagnetic field distributed in the vicinity of a quantum dash inside a processed mesa.
Źródło:
Acta Physica Polonica A; 2016, 129, 1a; A-48-A-52
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic Structure of Elongated $In_{0.3}Ga_{0.7}As//GaAs$ Quantum Dots
Autorzy:
Pieczarka, M.
Musiał, A.
Podemski, P.
Sęk, G.
Misiewicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/1399091.pdf
Data publikacji:
2013-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
73.21.La
73.22.-f
Opis:
In this contribution the electronic structure of large $In_{0.3}Ga_{0.7}As//GaAs$ quantum dots is studied theoretically by means of 8 band k · p modeling. These quantum dots constitute unique physical system due to the low strain limit of the Stranski-Krastanow growth mode resulting in relatively large physical volume and elongation of the quantum dots in [1-10] direction. As a result of these critical growth conditions the electronic structure is expected to be very sensitive to the nanostructure size, shape, and composition of the quantum dot as well as the accompanying wetting layer. Another peculiarity of investigated system is the confining potential which is rather shallow and weakened in comparison to standard quantum dots. It makes them very interesting in view of both fundamental study and potential applications. To reveal physical mechanisms determining the optical properties of the investigated system, the electronic structure, mainly the number of confined states, and the wave function extension as a function of both quantum dot size and geometry have been simulated numerically and the importance of electron-hole Coulomb interactions has been evaluated.
Źródło:
Acta Physica Polonica A; 2013, 124, 5; 809-812
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Energy Transfer Processes in InAs/GaAs Quantum Dot Bilayer Structure
Autorzy:
Pieczarka, M.
Maryński, A.
Podemski, P.
Misiewicz, J.
Spencer, P.
Murray, R.
Sęk, G.
Powiązania:
https://bibliotekanauki.pl/articles/1185237.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
71.35.-y
78.55.-m
Opis:
We investigate double layer InAs/GaAs quantum dots grown in the Stransky-Krastanov mode by molecular beam epitaxy. The sample consists of two layers of InAs quantum dots separated by 10 nm thick GaAs layer, where the top quantum dot layer of an improved homogeneity is covered by an InGaAs cap. This configuration has allowed for the extension of the dots' emission to longer wavelengths. We probed the carrier transfer between the states confined in a double quantum well composed of InGaAs cap and the quantum dots wetting layer to the states in the quantum dots by means of photoluminescence excitation and photoreflectance spectroscopies. Efficient emission from quantum dots excited at the double quantum well ground state energy was observed. There is also presented a discussion on the carrier injection efficiency from the capping layer to the quantum dots.
Źródło:
Acta Physica Polonica A; 2016, 129, 1a; A-59-A-61
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Frequency Discrimination for Amplitude Modulated Sinusoidal Signals at High Carrier Frequencies
Autorzy:
Sęk, A.
Kordus, M.
Powiązania:
https://bibliotekanauki.pl/articles/1359956.pdf
Data publikacji:
2014-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.66.Fe
43.66.Hg
Opis:
The current study is a continuation of experiments presented by Sęk and Bukała (Acta Physica Polonica A 123, 1106 (2013)). The purpose of the present study was to investigate frequency discrimination of amplitude modulated high frequency carriers. Using 2AFC procedure, the subjects were presented with two observation intervals of which the first interval contained four pulses of the same high frequency signal (called SSSS), while in the second interval (called SHSH) the second and fourth pulses had higher frequencies values (i.e. shifted upwards by Δ f). The carrier frequency (in S pulses) was fixed and equal to 10 kHz. Modulation rates were equal to 100, 200, 337, 500, 600, 733, and 800 Hz. The value of the modulation rate was limited to keep all components of the sinusoidal modulation within one auditory filter (17% of the center frequency) centered at the carrier frequency. Two different types of modulation were used: a simple sinusoidal modulation with the modulation depth m set to 100%, and a logarithmic modulation with the modulation depth m set to 50 dB. Results indicate a strong relationship between frequency discrimination threshold and modulation type. The thresholds are significantly higher for logarithmic modulation in comparison to sinusoidal modulation. Amplitude modulation as well as logarithmic modulation applied to the high frequency carrier cause significant increase in the frequency discrimination threshold. For high frequency sinusoidal signal carriers (i.e. close to 10 kHz), frequency discrimination thresholds do not depend on amplitude modulation rates up to about 800 Hz. In general, the excitation pattern mechanism was a primary cue enabling frequency discrimination of modulated and unmodulated signals to compare with the mechanism based on the temporal fine structure. However, the excitation pattern was not the only mechanism responsible for the frequency discrimination.
Źródło:
Acta Physica Polonica A; 2014, 125, 4A; A-149-A-154
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
GaAs-Based Quantum Well Exciton-Polaritons beyond 1 μm
Autorzy:
Pieczarka, M.
Podemski, P.
Musiał, A.
Ryczko, K.
Sęk, G.
Misiewicz, J.
Langer, F.
Höfling, S.
Kamp, M.
Forchel, A.
Powiązania:
https://bibliotekanauki.pl/articles/1399094.pdf
Data publikacji:
2013-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.-b
78.67.-n
78.67.Pt
Opis:
Realization of the Bose-Einstein condensate can provide a way for creation of an inversion-free coherent light emitter with ultra-low threshold power. The currently considered solutions provide polaritonic emitters in a spectral range far below 1 μm limiting their application potential. Hereby, we present optical studies of InGaAs/GaAs based quantum well in a cavity structure exhibiting polaritonic eigenmodes from 5 to 160 K at a record wavelength exceeding 1 μm. The obtained Rabi splitting of 7 meV was almost constant with temperature, and the resulting coupling constant is close to the calculated QW exciton binding energy. This indicates the very strong coupling conditions explaining the observation of polaritons at temperatures where the exciton dissociation is already expected, and allows predicting that room temperature polaritons could still be formed in this kind of a system.
Źródło:
Acta Physica Polonica A; 2013, 124, 5; 817-820
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hole Subband Mixing and Polarization of Luminescence from Quantum Dashes: A Simple Model
Autorzy:
Kaczmarkiewicz, P.
Musiał, A.
Sęk, G.
Podemski, P.
Machnikowski, P.
Misiewicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/2048063.pdf
Data publikacji:
2011-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
73.22.-f
Opis:
In this paper, we address the problem of luminescence polarization in the case of nanostructures characterized by an in-plane shape asymmetry. We develop a simple semi-qualitative model revealing the mechanism that accounts for the selective polarization properties of such structures. It shows that they are not a straightforward consequence of the geometry but are related to it via valence subband mixing. Our model allows us to predict the degree of polarization dependence on the in-plane dimensions of investigated structures assuming a predominantly heavy hole character of the valence band states, simplifying the shape of confining potential and neglecting the influence of the out-of-plane dimension. The energy dependence modeling reveals the importance of different excited states in subsequent spectral ranges leading to non-monotonic character of the degree of polarization. The modeling results show good agreement with the experimental data for an ensemble of InAs/InP quantum dashes for a set of realistic parameters with the heavy-light hole states separation being the only adjustable one. All characteristic features are reproduced in the framework of the proposed model and their origin can be well explained and understood. We also make some further predictions about the influence of both the internal characteristics of the nanostructures (e.g. height) and the external conditions (excitation power, temperature) on the overall degree of polarization.
Źródło:
Acta Physica Polonica A; 2011, 119, 5; 633-636
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
InAs on InP Quantum Dashes as Single Photon Emitters at the Second Telecommunication Window: Optical, Kinetic, and Excitonic Properties
Autorzy:
Mrowiński, P.
Dusanowski, Ł.
Somers, A.
Höfling, S.
Reithmaier, J.
Misiewicz, J.
Sęk, G.
Powiązania:
https://bibliotekanauki.pl/articles/1033861.pdf
Data publikacji:
2017-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
photoluminescence
quantum dash
excitonic complexes
antibunching
autocorrelation
single photon source
telecommunication
time-resolved
Opis:
In this work, InAs/InGaAlAs/InP quantum dashes have been investigated in terms of their optical, kinetic, and excitonic properties with respect to their application within the 1300± 40 nm spectral range, i.e. the O-band of the telecommunication technologies. We focused on the basic excitonic complexes such as neutral exciton, biexciton, and charged exciton, which have been identified by means of photoluminescence measurements. Emission and carriers' dynamics have been analyzed using rate equation model and fitting the experimental data obtained for both continuous-wave and pulsed excitation regimes. There has been found a significant impact of the charge carrier imbalance in the system and electron capturing rate on the dynamics of the optical and electronic transitions, which results in a high occupation of the negatively charged trion state. Autocorrelation measurements show clear antibunching of trion emission for non-resonant excitation which indicates a potential of such kind of emitters as single photon sources for short-range quantum communication schemes.
Źródło:
Acta Physica Polonica A; 2017, 132, 2; 382-386
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Built-in Electric Field on Forbidden Transitions in In_xGa$\text{}_{1-x}$As/GaAs Double Quantum Well by Three-Beam Photoreflectance
Autorzy:
Sęk, G.
Ryczko, K.
Misiewicz, J.
Bayer, M.
Wang, T.
Forchel, A.
Powiązania:
https://bibliotekanauki.pl/articles/2028844.pdf
Data publikacji:
2001-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.-r
78.66.-w
Opis:
Photoreflectance spectroscopy has been used to study optical transitions in In$\text{}_{0.045}$Ga$\text{}_{0.955}$As/GaAs double quantum well at 80 K. The derivative nature of this contactless electromodulation technique allows for the observation of excited state transitions in the low-dimensional structure including the symmetry-forbidden ones. Excitonic symmetry-forbidden transitions can be observed due to the effect of mixing of heavy and light hole excitons and/or due to some asymmetry in the structure. We have shown that the built-in electric field in the region of double quantum well is weak enough (less than 0.5 kV/cm) not to cause any significant energetic shift of features due to quantum confined Stark effect, on one hand. On the other hand, it is sufficient to change strongly the oscillator strength of forbidden transitions. To change the internal electric field, we have used photoreflectance in the three-beam mode with a third beam continuously illuminating the sample and causing changes of the built-in electric fields due to the photovoltage effect. This method works as a contactless forward bias and allows for a change of the field down to the flat band conditions. We have shown that changes of built-in electric field by amount of a few tenths of kV/cm can modify the intensity of forbidden transitions significantly. We show that, although the mixing of excitons is still important, a very weak built-in electric field can be dominant in the observation of forbidden excitonic transitions in double quantum well.
Źródło:
Acta Physica Polonica A; 2001, 100, 3; 417-424
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 29

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