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Wyświetlanie 1-15 z 109
Tytuł:
Collective Spontaneous Emission from a System of Quantum Dots
Autorzy:
Abdussalam, W.
Machnikowski, P.
Powiązania:
https://bibliotekanauki.pl/articles/1403617.pdf
Data publikacji:
2012-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
42.50.Ct
03.65.Yz
Opis:
We study the spontaneous emission from a regular lateral array or a randomly distributed ensemble of quantum dots under strong excitation (full inversion) conditions. We focus on the similarities and differences between the cases of random and regular arrangement of the dots and show that there is very little difference between the evolution of luminescence in these two cases, both for identical dots and for a realistically inhomogeneously broadened ensemble. This means that the enhanced emission or superradiance effect is not due to accidental clustering of pairs of dots. Moreover, we point out that observation of an enhanced emission under weak excitation does not prove that true superradiance will develop in a fully inverted system.
Źródło:
Acta Physica Polonica A; 2012, 122, 6; 994-996
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Collective Spontaneous Emission from Pairs of Quantum Dots: Long-Range vs. Short-Range Couplings
Autorzy:
Abdussalam, W.
Machnikowski, P.
Powiązania:
https://bibliotekanauki.pl/articles/1492857.pdf
Data publikacji:
2011-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
42.50.Ct
03.65.Yz
Opis:
We study the spontaneous emission from a coherently delocalized exciton state in a double quantum dot as a function of the distance between the dots, focusing on the similarities and differences between the cases of radiative (long-range, dipole) and tunnel coupling between the excitons in the dots. We show that there may be no qualitative difference between the collective emission induced by these two coupling types in spite of their essentially different physical properties.
Źródło:
Acta Physica Polonica A; 2011, 120, 5; 865-867
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sub-Nanosecond Phase Recovery in Quantum-Dot Semiconductor Optical Amplifiers
Autorzy:
Abedi, K.
Taleb, H.
Powiązania:
https://bibliotekanauki.pl/articles/1399957.pdf
Data publikacji:
2013-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.Eq
78.67.-n
78.67.Hc
Opis:
In this paper, optimal design of a pumping scheme for achieving the best gain and phase response in quntum-dot semiconductor optical amplifiers is investigated. For the first time, the dynamic response of the quntum-dot semiconductor optical amplifier is evaluated under three different pumping schemes, known as optical pumping, electrical pumping, and electro-optical pumping. Simulation results show that the shortest gain recovery time in quntum-dot semiconductor optical amplifiers can be achieved under the electrical pumping scheme. However, under the optical pumping and electro-optical pumping schemes, the quntum-dot semiconductor optical amplifier represents a shorter phase recovery compared to the electrical pumping scheme. We found that a sub-nanosecond phase recovery in the quntum-dot semiconductor optical amplifier can be achieved under the OP and electro-optical pumping schemes, which can never be achieved under the electrical pumping, because of the slow carrier dynamics of the carrier reservoir. Also, it was found that the gain recovery process in an optically pumped quntum-dot semiconductor optical amplifier can be significantly accelerated at cryogenic temperatures. This result demonstrates the superiorities of the optical pumping scheme over the electrical pumping and electro-optical pumping schemes at low temperatures, where both the gain and phase recovery times of an optically pumped quantum-dot semiconductor optical amplifier are drastically decreased.
Źródło:
Acta Physica Polonica A; 2013, 123, 2; 407-410
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Coherent Manipulations in Semiconductor Nanostructures
Autorzy:
Amand, T.
Marie, X.
Renucci, P.
Vanelle, E.
Powiązania:
https://bibliotekanauki.pl/articles/2027458.pdf
Data publikacji:
2001-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.50.Md
71.35.Ji
71.36.+c
78.47.+p
78.67.De
78.67.Hc
Opis:
This contribution presents recent results on spin manipulation by optical pulses in various semiconductor nanostructures such as quantum wells, microcavities, quantum dots. The potentialities of temporal coherent control, as well as spin dynamics under magnetic field are investigated, using the current ultrafast emission spectroscopy techniques.
Źródło:
Acta Physica Polonica A; 2001, 100, 2; 175-204
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Interband Optical Properties of Concentric Type-I Nanorings in a Normal Magnetic Field
Autorzy:
Arsoski, V.
Tadić, M.
Peeters, F.
Powiązania:
https://bibliotekanauki.pl/articles/1537829.pdf
Data publikacji:
2010-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.67.Hc
Opis:
Two concentric two-dimensional GaAs/(Al,Ga)As nanorings in a normal magnetic field are theoretically studied. The single-band effective mass approximation is adopted for both the electron and the hole states, and the analytical solutions are given. We find that the electronic single particle states are arranged in pairs, which exhibit anticrossings and the orbital momentum transitions in the energy spectrum when magnetic field increases. Their period is essentially determined by the radius of the outer ring. The oscillator strength for interband transitions is strongly reduced close to each anticrossing. We show that an optical excitonic Aharonov-Bohm effect may occur in concentric nanorings.
Źródło:
Acta Physica Polonica A; 2010, 117, 5; 733-737
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hybrid Quantum Dot-Metal Nanoparticle Systems: Connecting the Dots
Autorzy:
Artuso, R.
Bryant, G.
Powiązania:
https://bibliotekanauki.pl/articles/1419509.pdf
Data publikacji:
2012-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Mf
73.21.La
78.67.Bf
78.67.Hc
Opis:
Hybrid molecules formed by coupling semiconductor quantum dots to metal nanoparticle nanoantennas provide a new paradigm for directed nanoscale transfer of quantum information. To assess this possibility, we study theoretically the response of these hybrid molecules to applied optical fields. Quantum-coherent time-evolution of the semiconductor quantum dots in the hybrid molecule is found by solving the semiconductor quantum dot density matrix equations. We study hybrid molecules in the weak and strong coupling regimes. In strongly driven, strongly dipole-coupled semiconductor quantum dot-metal nanoparticle hybrids with spherical metal nanoparticles, interference, dispersion near resonance and self interaction define the metal nanoparticle/semiconductor quantum dot coupling and lead to the Fano resonances, exciton induced transparency, suppressed semiconductor quantum dot response and bistability. More complicated response can be tailored by using metal nanoparticle shape and the placement of semiconductor quantum dots to control the local near-fields that couple the metal nanoparticles and semiconductor quantum dots. We describe how coupling to metal nanoparticle dark modes and higher order multipolar modes impact interference and self-interaction effects. The physics of the metal nanoparticle/semiconductor quantum dot coupling is outlined.
Źródło:
Acta Physica Polonica A; 2012, 122, 2; 289-293
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Growth and Characterization of Non-Linear Optical Single Crystal: L-cysteine Hydrochloride Monohydrate
Autorzy:
Azeezaa, V.
Arul Pragasam, A.
Sunitha, T.
Koteeswari, P.
Suresh, S.
Powiązania:
https://bibliotekanauki.pl/articles/1401908.pdf
Data publikacji:
2015-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.10.Dn
78.20.Ci
67.55.Hc
Opis:
Nonlinear optical single crystals of L-cysteine hydrochloride monohydrate (LCB) were grown by slow evaporation technique. Single crystal X-ray diffraction analysis revealed the crystal system and helped to determine lattice parameter values. Powder X-ray diffraction analyses were carried out and the diffraction patterns were indexed. The optical properties of the crystals were determined using UV-visible spectroscopy. Optical constants such as refractive index, extinction coefficient and electric susceptibility were determined from UV-visible spectroscopy. The Fourier transform infrared studies confirmed the various functional groups present in the grown crystal. The mechanical behaviour of the grown crystals was studied using Vicker's microhardness tester. The thermal analysis confirmed that the crystal was stable up to 108.7°C. The dielectric constant and the dielectric loss measurements were carried out for different temperatures and frequencies. Second harmonic generation of LCB crystal was investigated by the Kurtz powder technique.
Źródło:
Acta Physica Polonica A; 2015, 128, 3; 423-430
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Neutral and Charged Excitons Localized in the InAs/GaAs Wetting Layer
Autorzy:
Babiński, A.
Czyż, M.
Golnik, A.
Borysiuk, J.
Kret, S.
Raymond, S.
Lapointe, J.
Wasilewski, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1811914.pdf
Data publikacji:
2008-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.55.Cr
78.67.Hc
Opis:
It has recently been shown that potential fluctuations in a wetting layer, which accompanies InAs/GaAs quantum dots can localize excitons. Neutral excitons and biexcitons and charged excitons were identified. In this communication we report on studies of properties of the excitons over wide temperature range (T < 70 K). The micro-photoluminescence measurements enable investigation of excitons localized in a single potential fluctuation. Temperature-induced broadening of the neutral exciton as well as a quenching of the charged exciton at temperatures higher than 50 K are observed and discussed.
Źródło:
Acta Physica Polonica A; 2008, 114, 5; 1055-1060
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical Spectroscopy of Quantum Dots in High Magnetic Fields
Autorzy:
Babiński, A.
Powiązania:
https://bibliotekanauki.pl/articles/2046951.pdf
Data publikacji:
2006-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
78.55.Cr
75.75.+a
Opis:
Optical spectroscopy measurements of single InAs/GaAs self-assembled quantum dots have been performed. The multiexcitonic emission from the s-, p-, and d-shells of a single dot is observed and investigated in magnetic field up to 28 T. The Zeeman splitting of the s-shell excitons has been found to depend on the dot morphology. While the energy-splitting in flat (2 nm height) dots linearly increases with magnetic field, its significant non-linearity is observed for larger in size, tall (4 nm height) dots. The effect of magnetic field on the orbital motion of carriers in dots has also been investigated. It has been found that the modified Fock-Darwin pattern explains the observed evolution of the emission from highly-excited single tall quantum dot.
Źródło:
Acta Physica Polonica A; 2006, 110, 3; 275-286
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nano-Optics on Individual Quantum Objects - From Single to Coupled Semiconductor Quantum Dots
Autorzy:
Bacher, G.
Schömig, H.
Welsch, M. K.
Scheibner, M.
Seufert, J.
Obert, M.
Forchel, A.
Maksimov, A. A.
Zaitsev, S.
Kulakovskii, V. D.
Powiązania:
https://bibliotekanauki.pl/articles/2035563.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
75.50.Pp
73.21.La
Opis:
Some recent highlights of our optical studies on single and coupled semiconductor quantum dots are reviewed. In the first part, we concentrate on the role of spins and spin-spin interaction in nonmagnetic and magnetic single quantum dots. In the case of strictly resonant excitation of the ground state in self-assembled CdSe/ZnSe quantum dots, we find an exciton spin relaxation time, which exceeds the recombination lifetime significantly. Linear polarization has to be used for these experiments, as the electron-hole exchange interaction lifts the spin degeneracy and the eigenstates are linear combinations of spin-up and spin-down excitons. In a magnetic quantum dot, the exchange interaction between carrier spins and the spins of magnetic ions is shown to be responsible for giant magneto-optical effects. We demonstrate the formation of zero-dimensional magnetic polarons and we succeeded in measuring the magnetization on a scale of a few nanometers using the characteristic photoluminescence signal of individual quantum dots as experimental monitor. The second part is devoted to pairs of single quantum dots. On one hand, single exciton tunneling within an individual quantum dot pair is demonstrated studying single pairs of vertically correlated strain-induced and self-organized quantum dots. On the other hand, we show that in a pair of lithographically defined single dots with strongly different g-factors the energy spacing between the dot ground states can be tuned in an external magnetic field by about 10 meV, giving access to a controlled coupling between two individual quantum dots.
Źródło:
Acta Physica Polonica A; 2002, 102, 4-5; 475-494
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical Properties of Manganese-Doped Individual CdTe Quantum Dots
Autorzy:
Besombes, L.
Léger, Y.
Maingault, L.
Ferrand, D.
Bougerol, C.
Mariette, H.
Cibert, J.
Powiązania:
https://bibliotekanauki.pl/articles/2043698.pdf
Data publikacji:
2005-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
78.55.Et
75.75.+a
Opis:
The magnetic state of a single magnetic ion (Mn$\text{}^{2+}$) embedded in an individual quantum dot is optically probed using microspectroscopy. The fine structure of a confined exciton in the exchange field of a single Mn$\text{}^{2+}$ ion (S=5/2) is analyzed in detail. The exciton-Mn$\text{}^{2+}$ exchange interaction shifts the energy of the exciton depending on the Mn$\text{}^{2+}$ spin component and six emission lines are observed at zero magnetic field. The emission spectra of individual quantum dots containing a single magnetic Mn atom differ strongly from dot to dot. The differences are explained by the influence of the system geometry, specifically the in-plane asymmetry of the quantum dot and the position of the Mn atom. Depending on both these parameters, one has different characteristic emission features which either reveal or hide the spin state of the magnetic atom. The observed behavior in both zero field and under magnetic field can be explained quantitatively by the interplay between the exciton-manganese exchange interaction (dependent on the Mn position) and the anisotropic part of the electron-hole exchange interaction (related to the asymmetry of the quantum dot).
Źródło:
Acta Physica Polonica A; 2005, 108, 4; 527-540
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Resonant Excitation of CdTe/ZnTe Quantum Dot Pairs as a Tool for Spectroscopic Study of the Excitonic p-States
Autorzy:
Bogucki, A.
Smoleński, T.
Goryca, M.
Koperski, M.
Wojnar, P.
Kossacki, P.
Powiązania:
https://bibliotekanauki.pl/articles/1399083.pdf
Data publikacji:
2013-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
78.55.Et
71.70.Gm
71.35.-y
Opis:
We propose a new method of obtaining a photoluminescence spectrum of a single quantum dot in a self-assembled system of CdTe/ZnTe quantum dots. The method is based on the resonant excitation of a coupled dots pair. The comparison of the spectra in resonance and out of resonance enables the identification of a well-isolated lines related to the excitonic p-states. The application of the method allows the basic characterisation of a quantum dot, including the measurements of linear anisotropy, the excitation power dependence, and the analysis of the photoluminescence in the magnetic field.
Źródło:
Acta Physica Polonica A; 2013, 124, 5; 788-790
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Intermediate Band Formation and Intraband Absorption for Electrons in an Inhomogeneous Chain of Quantum Dots
Autorzy:
Bragar, I.
Machnikowski, P.
Powiązania:
https://bibliotekanauki.pl/articles/1492856.pdf
Data publikacji:
2011-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.67.Hc
78.30.Fs
Opis:
We study the electron states of a chain of non-identical, vertically stacked quantum dots. We discuss how the pseudo-band formed of the ground states confined in the quantum dots disintegrates upon increasing the inhomogeneity of the electron energies and analyze the impact of localization on the intraband absorption from the pseudo-band to extended (bulk) states. We describe also the dependence of the intraband absorption spectrum on the quantum dot size.
Źródło:
Acta Physica Polonica A; 2011, 120, 5; 862-864
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spatially Resolved Micro-Luminescence from GaN/AlGaN Quantum Dots
Autorzy:
Chwalisz, B.
Wysmołek, A.
Bożek, R.
Stępniewski, R.
Pakuła, K.
Kossacki, P.
Golnik, A.
Baranowski, J. M.
Powiązania:
https://bibliotekanauki.pl/articles/2038084.pdf
Data publikacji:
2004-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.Cr
78.66.Fd
78.67.Hc
75.75.+a
68.65.Hb
Opis:
We report on the optical experiments performed on low density GaN/AlGaN quantum dots grown on sapphire substrate using SiN during the growth process. The existence of quantum dots in the investigated structures was confirmed by atomic force microscopy. Although macro-luminescence of the investigated structures consist of broad emission lines the micro-photoluminescence experiments performed with the spatial resolution of 0.25 μm revealed sharp emission lines from the individual quantum dot in the energy range of 3.20-3.55 eV. It is shown that the magnetic fields up to 7 T do not influence significantly the electronic states of the dots.
Źródło:
Acta Physica Polonica A; 2004, 105, 6; 517-521
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Atomistic Calculation of Coulomb Interactions in Semiconductor Nanocrystals: Role of Surface Passivation and Composition Details
Autorzy:
Chwastyk, M.
Różanski, P.
Zieliński, M.
Powiązania:
https://bibliotekanauki.pl/articles/1419534.pdf
Data publikacji:
2012-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.21.La
78.67.Bf
78.67.Hc
73.20.Fz
71.15.-m
Opis:
We report a theoretical investigation of electronic properties of semiconductor InAs and GaAs nanocrystals. Our calculation scheme starts with the single particle calculation using atomistic tight-binding model including spin-orbital interaction and d-orbitals. Then the exciton binding energies are calculated with screened Coulomb interaction. We study the role of surface passivation effects by varying value of surface passivation potential. We compare results obtained with dot center positioned on different lattice sites thus containing different number of anion and cations. We conclude that passivation of surface states affects significantly single particle energies and the value of electron-hole Coulomb attraction. Interestingly, due to limited screening, the short-range (on-site) contribution to the electron-hole Coulomb attraction plays significant role for small nanocrystals with radius smaller than 1 nm.
Źródło:
Acta Physica Polonica A; 2012, 122, 2; 324-328
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 109

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