| 1. |
- Hessmo, B., et al.
(author)
-
Entangled states in interferometry
- 2002
-
In: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 101:1, s. 37-46
-
Journal article (peer-reviewed)abstract
- We show how some entangled quantum states can be used to improve interferometric measurements. We describe why Schrodinger-cat states are very sensitive to relative-phase shifts and why relative-phase states as described by A. Luis and L.L. Sanchez-Soto resolve the interval [0, 2pi] well. We also describe how the quantum concept of well-defined relative-phase and the classical visibility of an interference pattern are related.
|
|
| 2. |
- Ivanov, VY, et al.
(author)
-
Microwave-induced delocalization of excitons in ternary compounds of II-VI and III-V semiconductors
- 2003
-
In: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 103:6, s. 559-566
-
Journal article (peer-reviewed)abstract
- In this work we employ technique of optically detected cyclotron resonance for evaluation of the role of localization processes in CdTe/CdMnTe and CdMnTe/CdMgTe quantum well structures. From microwave-induced changes of excitonic emissions we evaluate magnitude of potential fluctuations (Stokes shift), correlate optically detected cyclotron resonance results with the results of time-resolved experiments and discuss nature of recombination processes in the limit of a strong localization.
|
|
| 3. |
- Jaskorzynska, Bozena, et al.
(author)
-
Nonlinear upconversion-rate in Er-doped fibers
- 2001
-
In: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 99:1, s. 147-153
-
Journal article (peer-reviewed)abstract
- Energy transfer between excited rare-earth ions has been widely used for realizing upconversion lasers and also recognized as a gain limiting factor in high-concentration Er-doped amplifiers. The energy transfer leads to upconversion of the excitation which for randomly distributed (not clustered) ions is called homogeneous upconversion. It was commonly assumed that the rate of homogeneous upconversion is a linear function of the population inversion N-2. However, recently published Monte Carlo simulations predict that the homogeneous upconversion rate is a nonlinear function of N-2 and that it, moreover, depends on the pump and signals rates. In this paper we review some of our experimental results confirming those predictions. We also propose a statistical, analytical model describing the observed homogeneous upconversion behavior in Er-doped fibers.
|
|
| 4. |
- Khoptyar, D., et al.
(author)
-
Steady-state and switch-off behavior of upconversion in Er-doped fibers
- 2003
-
In: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 103:03-feb, s. 207-210
-
Journal article (peer-reviewed)abstract
- By measuring the metastable and the upconverted fluorescence in Er-doped fibers we determine rate of homogeneous upconversion as a function of the population inversion. The results confirm the prediction of our statistical model that at the same population inversion the upconversion rates under the steady-state and the switch-off conditions are different. The larger rate of the steady state upconversion is attributed to the pump enhanced, redistribution of the excitation energy.
|
|
| 5. |
- Nikolaenko, Y. M., et al.
(author)
-
Fast bolometric response of bulk La0.7Sr0.3MnO3 electroceramic structures
- 2000
-
In: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 97:6, s. 991-995
-
Journal article (peer-reviewed)abstract
- We report on the performance of a microwave electroceramic bolometer of hybrid La0.7Sr0.3MnO3/Al2O3 (0.2 x 2 x 4 mm(3)) structure. The estimated thermal resistance of the bulk ceramic manganite film-single crystal sapphire interface is about 500 K/W at room temperature. This resistance is the main thermal barrier in the heat sink system and has been found to be slightly dependent on temperature, When compared with the high-ire superconducting bolometers, the La0.7Sr0.3MnO3 microwave electroceramic bolometer works in a more wide temperature range, from 77 K to 330 K, excluding the narrow temperature interval at the metal-insulator phase transition (T = 230 K). The microwave electroceramic bolometer sensitivity and the time constant at room temperature have been found to be 0.1 V/W and 100 ms, respectively. To improve the bolometer performance the point contact has been fabricated by a break junction technique. The optimization of a microwave electroceramic bolometer design brought to a considerable improvement of basic bolometer characteristics. The microwave sensitivity was about 0.3 V/W and the time constant was less than 100 ns.
|
|
| 6. |
- Willander, Magnus, et al.
(author)
-
Optical properties of InAs quantum dots
- 2002
-
In: Acta Physica Polonica. A. - : Polish Academy of Sciences Warsaw. - 0587-4246 .- 1898-794X. ; 102:4-5, s. 567-576
-
Journal article (peer-reviewed)abstract
- InAs quantum dots grown on GaAs substrate were investigated by optical spectroscopy. We particularly emphasized on the photoluminescence intensity, the stability of the photoluminescence intensity versus temperatures and wavelength of the InAs dot emission at various thermal treatments and different structures. We found that hydrogen can strongly passivate nonradiative centers without causing any structure degradation, and both n- and p-type modulation doping can reduce the decrease in the photoluminescence intensity when the sample temperature increases from the helium temperature to room temperature. The emission wavelength and the efficiency of the InAs quantum dots can also be manipulated by choosing proper materials of cap layer.
|
|
| 7. |
- Fedorych, OM, et al.
(author)
-
Electrically detected magnetic resonance
- 2004
-
In: Acta Physica Polonica. Series A: General Physics, Physics of Condensed Matter, Optics and Quantum Electronics, Atomic and Molecular Physics, Applied Physics. - 0587-4246. ; 105:6, s. 591-598
-
Journal article (peer-reviewed)abstract
- We compare the results of electrically detected magnetic resonance in a 2D electron gas in Si/SiGe quantum wells with transport and magnetic resonance measurements on ferromagnetic Ga1-xMnxAs. The results lead us to the conclusion that observation of electrically detected magnetic resonance is possible only in the case of a slow spin relaxation, where the microwave resonant absorption leads to a noticeable change of spin magnetization.
|
|
| 8. |
- Figielski, T, et al.
(author)
-
Magnetotransport through nanoconstriction in ferromagnetic semiconductor (Ga,Mn)As
- 2003
-
In: Acta Physica Polonica A ( Proceedings of the XXXII International School on Physics of Semiconducting Compounds, Part 1). - 0587-4246. ; 103:6, s. 525-531
-
Conference paper (peer-reviewed)abstract
- We studied narrow (submicron) constrictions in the layers of ferromagnetic semiconductor (Ga, Mn)As. We have demonstrated a contribution of the quantum localization effects to the magnetoresistance of the constricted samples. We have also found a negative contribution of a domain wall trapped in the constriction to the resistance, due presumably to the erasing of the localization effects by the domain wall.
|
|
| 9. |
- Hernandez, C, et al.
(author)
-
Magnetic properties of GaMnAs single layers and GaInMnAs superlattices investigated at low temperature and high magnetic field
- 2003
-
In: Acta Physica Polonica. Series A: General Physics, Physics of Condensed Matter, Optics and Quantum Electronics, Atomic and Molecular Physics, Applied Physics. - 0587-4246. ; 103:6, s. 613-619
-
Journal article (peer-reviewed)abstract
- Magnetotransport properties of GaMnAs single layers and InGaMnAs/ InGaAs superlattice structures were investigated at temperatures from 4 K to 300 K and magnetic fields up to 23 T to study the influence of carriers confinement through different structures. Both single layers and superlattice structures show paramagnetic-to-ferromagnetic phase transition. In GaMnAs/InGaAs superlattice beside the Curie temperature (T-c approximate to 40 K), a new phase transition is observed close to 13 K.
|
|
| 10. |
- Kowalski, BJ, et al.
(author)
-
MnAs overlayer on GaN(000(1)under-bar)-(1 x 1) its growth, morphology and electronic structure
- 2004
-
In: Acta Physica Polonica. Series A: General Physics, Physics of Condensed Matter, Optics and Quantum Electronics, Atomic and Molecular Physics, Applied Physics. - 0587-4246. ; 105:6, s. 645-650
-
Journal article (peer-reviewed)abstract
- MnAs layer has been grown by means of MBE on the GaN(000 (1) under bar)-(1 x 1) surface. Spontaneous formation of MnAs grains with a diameter of 30-60 nm (as observed by atomic force microscopy) occurred for the layer thickness bigger than 7 ML. Ferromagnetic properties of the layer with Curie temperature higher than 330 K were detected by SQUID measurements. Electronic structure of the system was investigated in situ by resonant photoemission spectroscopy for MnAs layer thickness of 1, 2, and 8 ML. Density of the valence band states of MnAs and its changes due to the increase in the layer thickness were revealed.
|
|
