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Tytuł:
The Use of the Phase Locking Information in the Human Auditory System for Frequencies Above 5 kHz
Autorzy:
Sęk, A.
Bukała, M.
Powiązania:
https://bibliotekanauki.pl/articles/1400102.pdf
Data publikacji:
2013-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.66.Fe
43.66.Hg
Opis:
Accurate allocation of neural impulses to the same phase (i.e. phase locking) in the auditory system, ceases for frequencies above 5 kHz. However, some recent works suggest that it may have a much higher value. A discrimination of harmonic complex and inharmonic complex sound, formed using sound harmonic complex, in which all components were shifted towards higher frequency by the same number in hertzs, was analyzed. Fundamental frequency was $F_0$=1 kHz and signals were bandpass filtered by a fixed filter center frequency of which was $11F_0$ and bandwidth $5F_0$. Discrimination threshold was $\Delta F=0.089F_0$ for 10 normal-hearing subjects. However, replacing the sinusoidal components with the noise bands brought about a significant increase in thresholds. The largest increase was observed for 700 Hz bandwidth. The replacement of sinusoidal components with noisebands reduces information conveyed by phase locking. The differences in excitation pattern for harmonic complex and inharmonic complex signals, for the average threshold, did not exceed 0.7 dB. Therefore they could not be a useful cue for harmonic complex and inharmonic complex discrimination. A simplified model of phase locking showed that the substitution of sinusoids with bands of noise significantly reduced number of intervals between successive neural spikes corresponding to the virtual pitch of harmonic complex and inharmonic complex sounds. This degradation of discrimination suggests that the main source of information about the pitch of harmonic complex and inharmonic complex, especially for sinusoidal components, was the phase locking.
Źródło:
Acta Physica Polonica A; 2013, 123, 6; 1106-1113
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Phonon-Assisted Radiative Recombination of Excitons Confined in InAs Quantum Dashes
Autorzy:
Dusanowski, Ł.
Musiał, A.
Sęk, G.
Machnikowski, P.
Powiązania:
https://bibliotekanauki.pl/articles/1399092.pdf
Data publikacji:
2013-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
63.20.kk
Opis:
In this report we have investigated theoretically the phonon-assisted recombination process of excitons confined in strongly elongated semiconductor nanostructures, called quantum dashes. Interaction with phonon bath leads to the occurrence of phonon-assisted recombination, which in the case of acoustic phonons is manifested in the optical spectra as a deviation of the homogeneously broadened emission line shape from expected Lorentzian profile via occurrence of the so-called phonon sidebands. Hereby, we have modeled the influence of the quantum dash geometry on this spectral feature proving pronounced suppression of phonon-induced decoherence for strongly elongated nanostructures. Furthermore, the importance of different phonon coupling mechanisms has been evaluated and the spectral diffusion effects, unavoidable in the time-integrated photoluminescence experiments, have been accounted for.
Źródło:
Acta Physica Polonica A; 2013, 124, 5; 813-816
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of the Semantic Material on the Assessment of Speech Reception Threshold
Autorzy:
Krenz, M.
Wicher, A.
Sęk, A.
Powiązania:
https://bibliotekanauki.pl/articles/178107.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
speech intelligibility
speech test
speech reception threshold
Opis:
To determine speech intelligibility using the test suggested by Ozimek et al. (2009), the subject composed sentences with the words presented on a computer screen. However, the number and the type of these words were chosen arbitrarily. The subject was always presented with 18, similarly sounding words. Therefore, the aim of this study was to determine whether the number and the type of alternative words used by Ozimek et al. (2009), had a significant influence on the speech intelligibility. The aim was also to determine an optimal number of alternative words: i.e., the number that did not affect the speech reception threshold (SRT) and not unduly lengthened the duration of the test. The study conducted using a group of 10 subjects with normal hearing showed that an increase in the number of words to choose from 12 to 30 increased the speech intelligibility by about 0.3 dB/6 words. The use of paronyms as alternative words as opposed to random words, leads to an increase in the speech intelligibility by about 0.6 dB, which is equivalent to a decrease in intelligibility by 15 percentage points. Enlarging the number of words to choose from, and switching alternative words to paronyms, led to an increase in response time from approximately 11 to 16 s. It seems that the use of paronyms as alternative words as well as using 12 or 18 words to choose from is the best choice when using the Polish Sentence Test (PST).
Źródło:
Archives of Acoustics; 2015, 40, 1; 41-50
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of a Single Therapeutic Dose of Methadone on Selected Auditory Functions in Patients Addicted to Opioids and Undergoing Substitution Therapy – a Preliminary Study
Autorzy:
Tarnowska, E.
Wicher, A.
Sęk, A.
Gorzelańczyk, E. J.
Powiązania:
https://bibliotekanauki.pl/articles/176565.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
methadone
opioids
speech intelligibility
otoacoustic emissions
hearing threshold
Opis:
The main purpose of this research was to determine the influence of a therapeutic dose of an opioid drug (methadone) on selected auditory functions in patients addicted to opioids (recognition ICD-10; F11) and undergoing substitution therapy. Various hearing tests were used in this research – pure tone audiometry, impedance audiometry, otoacoustic emission measurement, and a speech in noise test – in two sessions, before and after methadone intake. It was found that methadone causes an improvement in speech intelligibility when speech is presented in speech-like noise, and slightly decreases hearing thresholds [dB HL]. Methadone consumption has no significant impact on distortion product otoacoustic emissions levels (DPOAE). In summary, a prescribed methadone dose does not worsen the hearing of opioid-dependent subjects.
Źródło:
Archives of Acoustics; 2018, 43, 1; 137-146
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Temperature Dependence of Photoluminescence from Epitaxial InGaAs/GaAs Quantum Dots with High Lateral Aspect Ratio
Autorzy:
Musiał, A.
Sęk, G.
Maryński, A.
Podemski, P.
Misiewicz, J.
Löffler, A.
Höfling, S.
Reitzenstein, S.
Reithmaier, J.
Forchel, A.
Powiązania:
https://bibliotekanauki.pl/articles/1492876.pdf
Data publikacji:
2011-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
65.80.-g
Opis:
Hereby, we present a study of a thermal quenching of emission from self-assembled epitaxial highly asymmetric quantum dots in InGaAs/GaAs material system for both ensemble and single dot regime. Pronounced interplay between the intensity of wetting layer and quantum dots originated emission was observed as the temperature was increased, evidencing a thermally activated energy transfer between the two parts of the system and an important role of the wetting layer in determining the optical properties of these anisotropic nanostructures. The carrier activation energies have been derived and possible carrier loss mechanisms have been analyzed. Single dot study revealed activation energies slightly varying from dot to dot due to size and shape distribution. The problem of the shape uniformity of individual quantum dot has also been addressed and possibility of additional carrier localization within the investigated structures has been found to be insignificant based on the recorded spectroscopic data.
Źródło:
Acta Physica Polonica A; 2011, 120, 5; 883-887
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Symulacje numeryczna procesu koalescencji w emulsjach spożywczych
Numerical simulations of coalescence proces in food emulsions
Autorzy:
Sęk, J.
Strzelecka, A.
Powiązania:
https://bibliotekanauki.pl/articles/2071653.pdf
Data publikacji:
2011
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
emulsja
koalescencja
śmietankowanie
symulacja numeryczna
emulsions
coalescence
creaming
numerical simulation
Opis:
Badano numerycznie proces koalescencji i śmietankowania w emulsjach. Stworzono modele numeryczne układów dwufazowych zawierających regularnie rozmieszczone krople fazy rozproszonej. Przeprowadzono symulacje zachowania się takich rojów w warunkach różnych wartości sił masowych i przy różnej średnicy kropel. Wykazano zgodność wyników uzyskanych za pomocą modeli numerycznych z wartościami wynikającymi z zależności teoretycznych. Stwierdzono również różny przebieg procesów śmietankowania i koalescencji w zależności od warunków przepływu.
Coalescence and creaming of emulsions were investigated numerically. Numerical models of two-phase systems containing regularly distributed droplets of dispersed phase were created. Numerical simulation of flow and behavior of those systems of droplets were performed for different values of body forces and for different droplet diameter. It was proved that the numerical models were compatible with the theoretical equations. A different course of coalescence and creaming process was observed depending on flow conditions.
Źródło:
Inżynieria i Aparatura Chemiczna; 2011, 1; 41-42
0368-0827
Pojawia się w:
Inżynieria i Aparatura Chemiczna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Revision of the amphibian genus Limnerpeton [Temnospondyli] from the Upper Carboniferous of the Czech Republic
Autorzy:
Milner, A R
Sequeira, S.E.K.
Powiązania:
https://bibliotekanauki.pl/articles/22128.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Temnospondyli
Carboniferous
Amphibia
Czech Republic
amphibian
Limnerpeton
paleontology
Dissorophoidea
Upper Carboniferous
Opis:
The Late Carboniferous amphibian genus Limnerpeton Fritsch, 1881 is revised on the basis of the type specimens of the eight original species described by Fritsch using material from Nýřany, Třemošná and Kounov, now in the Czech Republic. The type species Limnerpeton modestum is a nomen dubium restricted to a mandible that almost certainly belongs to an amphibamid temnospondyl but is not critically diagnostic. “Limnerpeton” laticeps and “Limnerpeton” macrolepis lectotypes are both small individuals of the same taxon as the later described Mordex calliprepes Steen, 1938 and thus form part of the hypodigm of Mordex laticeps comb. nov. “Limnerpeton” elegans is now Limnogyrinus elegans and is a member of the temnospondyl family Micromelerpetontidae. “Limnerpeton” obtusatum is a specimen of the microsaur Microbrachis pelikani. “Limnerpeton” dubium is an indeterminate tetrapod, probably either a temnospondyl or a pelycosaur. “Limnerpeton” difficile is a nomen dubium but the type is probably a small specimen of the tuditanomorph microsaur Crinodon limnophyes. “Limnerpeton” caducum is almost certainly a specimen of the ophiderpetontid aïstopod Oestocephalus granulosus. Several other described small temnospondyls from Nýřany are discussed and shown to be specimens of either Limnogyrinus elegans, Mordex laticeps or Amphibamidae incertae sedis. The tetrapod fauna at Nýřany includes four dissorophoid temnospondyls as proposed by Milner (1986) but with two changes in nomenclature. They comprise the branchiosaurid Branchiosaurus salamandroides, the micromelerpetontid Limnogyrinus elegans, the amphibamid Platyrhinops cf. lyelli and the primitive trematopid Mordex laticeps. These represent four of the five major dissorophoid families and demonstrate that the group had already diversified by the late Westphalian.
Źródło:
Acta Palaeontologica Polonica; 2003, 48, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Peculiarities in optical response of hybrid-barrier GaSb/InAs/AlSb resonant tunneling diode structure
Autorzy:
Dyksik, M.
Motyka, M.
Rygała, M.
Pfenning, A.
Hartmann, F.
Weih, R.
Worschech, L.
Höfling, S.
Sęk, G.
Powiązania:
https://bibliotekanauki.pl/articles/1835778.pdf
Data publikacji:
2021
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
resonant tunneling diode
quantum well
optical spectroscopy
photoluminescence
photoreflectance
Opis:
We present comprehensive investigation of the optical properties of hybrid-barrier GaSb-based resonant tunneling structures, containing a bulk-like GaInAsSb absorption layer and two asymmetric type II GaSb/InAs/AlSb quantum wells. Methods of optical spectroscopy by means of Fourier-transformed photoluminescence and photoreflectance are employed to probe optical transitions in this complex multilayer system. Based on the comparison between the absorption-like and emission-like spectra (also in function of temperature) confronted with band structure calculations four main transitions could be resolved and identified. For one of them, there has been observed unusually strong linear polarization dependence never reported in structures of that kind. It has been interpreted as related to a transition at the GaSb/GaInAsSb interface, for which various scenarios causing the polarization selectivity are discussed.
Źródło:
Optica Applicata; 2021, 51, 2; 171-180
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oscillator strength of optical transitions in InGaAsN/GaAsN/GaAs quantum wells
Autorzy:
Mika, A
Sek, G
Ryczko, K
Kozub, M
Musial, A
Marynski, A
Misiewicz, J
Langer, F
Höfling, S
Appel, T
Kamp, M
Forchel, A
Powiązania:
https://bibliotekanauki.pl/articles/173586.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
dilute nitride
quantum well
oscillator strength
Opis:
Experimental and theoretical considerations and results on the effect of nitrogen incorporation on the oscillator strength of optical transitions in InGaNAs/GaAs quantum wells (QWs) are presented. Therefore, a set of dilute nitride quantum well structures was grown by molecular beam epitaxy. Optical investigation via spectroscopic methods have been performed at various temperatures for both the as-grown samples, and after rapid thermal annealing. The fundamental transition energy and its oscillator strength vs. the QW composition have been systematically investigated. Additionally, the effect of the bandgap discontinuities on the transitions intensity has also been considered. The experimental data have been confronted with the band structure calculations within the effective mass approximation employing a two level repulsion model for the nitrogen-containing structures. The obtained results are crucial for possible future applications employing the quantum well in cavity structures and bringing the practical exploitation of quantum electrodynamics phenomena to the telecommunication spectral range.
Źródło:
Optica Applicata; 2013, 43, 1; 53-60
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimizing the InGaAs/GaAs quantum dots for 1.3 μm emission
Autorzy:
Maryński, A.
Mrowiński, P.
Ryczko, K.
Podemski, P.
Gawarecki, K.
Musiał, A.
Misiewicz, J.
Quandt, D.
Strittmatter, A.
Rodt, S.
Reitzenstein, S.
Sęk, G.
Powiązania:
https://bibliotekanauki.pl/articles/1055140.pdf
Data publikacji:
2017-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.30.Fs
78.67.-n
78.67.Hc
73.22.-f
Opis:
Hereby we present comprehensive experimental and theoretical study on fundamental optical properties and electronic structure of GaAs-based quantum dots grown using metalorganic chemical vapor deposition technique. The substantial redshift of emission, to the second telecommunication window of 1.3 μm, in comparison to standard InGaAs/GaAs quantum dots is obtained via strain engineering utilizing additional capping layer of In_{0.2}Ga_{0.8}As in this context referred to as strain reducing layer. It ensures lowering of the energy of the ground state transition to more application relevant spectral range. Optical properties of the quantum dot structure has been experimentally characterized by means of photoreflectance spectroscopy and power-dependent photoluminescence revealing 3 transitions originating from hybrid states confined in an asymmetric double quantum well formed of the wetting layer and strain reducing layer, as well as higher states of the quantum dots themselves with the first excited state transition separated by 67 meV from the ground state transition. Origin of the observed transitions was confirmed in theoretical modelling using 1-band single-particle approach for the quantum well part, and excitonic quantum dot spectrum obtained within 8 band k·p formalism followed by configuration interaction calculations, respectively. Additionally, photoluminescence excitation spectroscopy measurements allowed to identify a spectral range for efficient quasi-resonant excitation of the investigated quantum dots into the 2D density of states to be in the range of 835-905 nm.
Źródło:
Acta Physica Polonica A; 2017, 132, 2; 386-390
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical Trapping and Propagation of Nonresonantly Driven One-Dimensional Exciton-Polariton Condensate
Autorzy:
Opala, A.
Pieczarka, M.
Sęk, G.
Powiązania:
https://bibliotekanauki.pl/articles/1033879.pdf
Data publikacji:
2017-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
67.85.De
71.36.+c
03.75.Kk
Opis:
We study theoretically a nonresonant optical creation of a one-dimensional exciton-polariton condensate in a semiconductor microcavity. The polariton condensate is treated in the mean-field approach, taking into consideration an antitrapping potential created by the reservoir of noncondensed particles. Polariton condensates are excited by multiple lasers, with a combination of continuous wave and pulsed sources. The proposed pump-probe configuration leads to the realisation of various experimental schemes, e.g. optical trapping of a polariton condensate in real space. Moreover, it can be utilised for investigation of elementary excitations in the time domain when polariton condensates from two sources interact with each other.
Źródło:
Acta Physica Polonica A; 2017, 132, 2; 401-404
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical, Structural, and Electrical Properties of Aromatic Triphenylamine-Based Poly(azomethine)s in Thin Layers
Autorzy:
Palewicz, M.
Iwan, A.
Sikora, A.
Doskocz, J.
Strek, W.
Sek, D.
Mazurek, B.
Powiązania:
https://bibliotekanauki.pl/articles/1490096.pdf
Data publikacji:
2012-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.Jd
73.61.Ph
78.66.Qn
Opis:
Spectroscopic and photophysical properties of the poly(azomethine)s with triphenylamine moieties were investigated by UV-vis, X-ray diffraction and atomic force microscopy methods. Current-voltage measurements were performed on ITO/polymer/$Alq_3$/Al, ITO/PEDOT/polymer:MWCNT/Al and ITO/polymer:MWCNT/Al devices. Multiwall carbon nanotubes were blended with polymer in the ratio 1:1. The lowest optical band gap value at 2.33 eV was detected. Moreover, an absorption coefficient α was calculated from transmission and reflectivity measurements. In this paper, we presented photophysical and structural properties of the poly(azomethine)s in solid state of great interest for the emerging field of molecular electronics and for their uses as active layers in (opto)electronic devices such as solar cells.
Źródło:
Acta Physica Polonica A; 2012, 121, 2; 439-444
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On a small Cochleosaurus described as a large Limnogyrinus [Amphibia, Temnospondyli] from the Upper Carboniferous of the Czech Republic
Autorzy:
Milner, A R
Sequeira, S.E.K.
Powiązania:
https://bibliotekanauki.pl/articles/21039.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Carboniferous
Temnospondyli
Limnogyrinus
Czech Republic
Amphibia
Limnogyrinus elegans
Cochleosaurus
paleontology
Upper Carboniferous
Opis:
Limnogyrinus elegans (Fritsch) is the most primitive micromelerpetontid temnospondyl from the Upper Carboniferous of Nýřany, Czech Republic. Arecent revision of the taxon by Werneburg (1994) attributed to this species a skull in dorsal aspect which was significantly larger than any previously reported and showed evidence of snout elongation. Restudy of this specimen demonstrates it to be a skull, visible in ventral aspect, of a juvenile of Cochleosaurus bohemicus, a more primitive edopoid temnospondyl, which is frequent in the Nýřany assemblage. Werneburg’s diagnosis of Limnogyrinusis revised and the problems of constructing ontogenetic series are discussed.
Źródło:
Acta Palaeontologica Polonica; 2003, 48, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of the Non-Square InGaAsP/InP Quantum Wells in the Electric Field by Photoreflectance
Autorzy:
Kudrawiec, R.
Sęk, G.
Rudno-Rudziński, W.
Misiewicz, J.
Wojcik, J.
Robinson, B. J.
Thompson, D. A.
Mascher, P.
Powiązania:
https://bibliotekanauki.pl/articles/2035600.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.63.Hs
78.67.-n
66.10.Cb
Opis:
Non-square quantum wells in electric field have been investigated by photoreflectance and photoluminescence spectroscopies. The structures have been obtained by a post-growth modification (rapid thermal annealing) of standard 1.55μm InGaAsP-based laser structures that were grown by gas source molecular beam epitaxy. During rapid thermal annealing a migration of semiconductor atoms across quantum well interfaces changes the quantum well profile from a square well to a rounded well. The modification of the profile changes energy levels in the quantum well and in consequence a blue shift of the quantum well emission peak is observed in photoluminescence. In this paper the blue shift of the ground state transition of post-growth modified quantum well structures has been investigated by both photoluminescence and photoreflectance techniques. Also a blue shift of excited state transitions has been observed in photoreflectance spectra. Generally, a stronger blue shift for the ground state transition than for excited state transitions has been observed. Additionally, oscillator strengths for all quantum well transitions have been determined from photoreflectance spectra. It has been found that the oscillator strength is constant for all quantum well transitions despite of modification of the quantum well profile.
Źródło:
Acta Physica Polonica A; 2002, 102, 4-5; 649-657
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
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