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Wyświetlanie 1-7 z 7
Tytuł:
The Interplay of Intraband and Interband Polarization in the Ultrafast Response of Biased Semiconductor Superlattices
Autorzy:
Dignam, M. M.
Hawton, M.
Yang, L.
Rosam, B.
Powiązania:
https://bibliotekanauki.pl/articles/2041627.pdf
Data publikacji:
2005-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.47.+p
42.65.Re
78.67.-n
Opis:
We present the results of a new excitonic formalism for the treatment of ultrafast dynamics in asymmetric semiconductor multiple quantum well structures. The method is infinite order in the optical field, with truncation of the infinite hierarchy of dynamical equations being accomplished via a factorization of six-particle correlation functions into a product of two- and four-particle ones. We use this formalism to calculate the THz emission and degenerate four-wave mixing signals from biased semiconductor superlattices under different excitation conditions. We present a number of density-dependent effects that demonstrate the central role that the intraband polarization plays in determining and modifying the nonlinear ultrafast response of the system.
Źródło:
Acta Physica Polonica A; 2005, 107, 1; 56-64
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Grating Diffraction Effects in the THz Domain
Autorzy:
Coutaz, J.-K.
Garet, F.
Bonnet, E.
Tishchenko, A. V.
Parriaux, O.
Nazarov, M.
Powiązania:
https://bibliotekanauki.pl/articles/2041624.pdf
Data publikacji:
2005-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.47.+p
72.30.+q
42.65.Re
Opis:
We study the far infrared electromagnetic response of grating devices by THz time-domain spectroscopy. We first show that THz waves are efficiently injected into silicon waveguides using grating couplers. Moreover, changing the waveguide material parameters by white-light illumination allows us to strongly modify the coupling efficiency. Then we demonstrate resonant effects in segmented grating structures that act as perfect mirrors at selected wavelengths even for focused beams. About 10 periods of the grating participate in the phenomenon, nevertheless the resonance frequency width of the device remains narrow. This collection of experiments shows that millimeter-size mock-ups and THz waves can be effectively used to extrapolate the optical response of micron-size actual devices.
Źródło:
Acta Physica Polonica A; 2005, 107, 1; 26-37
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Efficient Terahertz Pulse Generation in Laser-Induced Gas Plasmas
Autorzy:
Löffler, T.
Kress, M.
Thomson, M.
Roskos, H. G.
Powiązania:
https://bibliotekanauki.pl/articles/2041638.pdf
Data publikacji:
2005-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.65.Re
72.30.+q
78.47.+p
Opis:
In this contribution, we review the development of sources for far-infrared (terahertz) radiation based on laser-generated gas plasmas. We describe several generation mechanisms based on ponderomotive forces, external field screening, and optical second-harmonic biasing. These methods are compared with the standard techniques with respect to the achievable terahertz pulse energy.
Źródło:
Acta Physica Polonica A; 2005, 107, 1; 99-108
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Low-Temperature MBE Grown GaAs for Pulsed THz Radiation Applications
Autorzy:
Adomavičius, R.
Balakauskas, S.
Bertulis, K.
Geižutis, A.
Molis, G.
Krotkus, A.
Powiązania:
https://bibliotekanauki.pl/articles/2041645.pdf
Data publikacji:
2005-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.65.Re
07.57.Hm
78.47.+p
Opis:
Attempts to optimize recombination characteristics of low-temperature MBE grown GaAs layers for their use in terahertz radiation devices are described and the characteristics of this material are compared with its alternative - As-ion implanted GaAs crystals.
Źródło:
Acta Physica Polonica A; 2005, 107, 1; 128-131
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Terahertz Emission from Narrow Gap Semiconductors Photoexcited by Femtosecond Laser Pulses
Autorzy:
Adomavičius, R.
Urbanowicz, A.
Molis, G.
Krotkus, A.
Powiązania:
https://bibliotekanauki.pl/articles/2041649.pdf
Data publikacji:
2005-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.65.Re
07.57.Hm
78.47.+p
72.30.+q
Opis:
Large increase in the emitted terahertz power was observed for p-InAs samples with the p-doping levels of approximately 10$\text{}^{16}$-10$\text{}^{17}$ cm$\text{}^{-3}$. This increase was explained by a large surface depletion layer and an electric-field-induced optical rectification effect in the layer. Terahertz fields radiated by the samples of all three investigated Cd$\text{}_{x}$Hg$\text{}_{1-x}$Te layers was of the same order of magnitude. No azimuthal angle dependence of the radiated signal was detected, which evidences that linear current surge effect is dominating over nonlinear optical rectification. Azimuthal angle and magnetic fields emission witness that it is caused by linear photo-Dember type processes.
Źródło:
Acta Physica Polonica A; 2005, 107, 1; 132-136
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical Pump - Terahertz Probe Measurement of the Electron Dynamics in Ga$\text{}_{1-x}$Mn$\text{}_{x}$As
Autorzy:
Šustavičiūtė, R.
Balakauskas, S.
Adomavičius, R.
Krotkus, A.
Sadowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/2047687.pdf
Data publikacji:
2007-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.65.Re
07.57.Hm
78.47.+p
75.50.Pp
Opis:
An optical pump - terahertz probe technique was used for measuring electron lifetime in various Ga$\text{}_{1-x}$Mn$\text{}_{x}$As epitaxial layers with the subpicosecond temporal resolution. The measurements were performed on the samples with x up to 2%, which had large resistivities and were transparent in a THz frequency range. It has been found that an induced THz absorption relaxation is the fastest and electron lifetimes are the shortest for the samples with the smallest Mn content. For the samples with x=0.3% and x=2% this relaxation becomes much slower; its rate is comparable to the carrier recombination rate in Ga$\text{}_{1-x}$Mn$\text{}_{x}$As substrate.
Źródło:
Acta Physica Polonica A; 2007, 112, 2; 311-314
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultrafast Coherent Terahertz Spectroscopy in High Magnetic Fields and Directed Energy Flows in Quantum Dot Assemblies
Autorzy:
Crooker, S. A.
Barrick, T.
Hollingsworth, J. A.
Klimov, V. I.
Powiązania:
https://bibliotekanauki.pl/articles/2036883.pdf
Data publikacji:
2003-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.65.Re
41.20.Jb
73.21.La
78.47.+p
Opis:
We describe the design, construction, and use of fiber-coupled terahertz antennas for performing ultrafast coherent THz spectroscopy directly in the cryogenic bore of high-field magnets. With an aim towards measuring the high-frequency (100 GHz to 2000 GHz) complex conductivity of correlated electron materials in the regime of low temperatures and high magnetic fields, these miniature THz emitters and receivers are demonstrated to work down to 1.5 K and up to 18 T, for eventual use in higher-field magnets. Results from a variety of semiconducting and superconducting samples are presented. This paper also describes a separate effort towards achieving coupling between colloidal semiconductor nanocrystal quantum dots, wherein we realize and study inter-dot communication via resonant (Förster) energy transfer. We present studies of the dynamics of resonant energy transfer in monodisperse and energy gradient (layered) assemblies of CdSe nanocrystal quantum dots. Time- and spectrally-resolved photoluminescence data directly reveal the energy-dependent transfer rate of excitons from smaller to larger dots. Results from layered nanocrystal quantum dot assemblies demonstrate unidirectional energy flows, a first step towards artificial light-harvesting structures. Lastly, time-resolved studies at millikelvin temperatures elucidate the nature of ground-state"dark" excitons in these quantum dots.
Źródło:
Acta Physica Polonica A; 2003, 104, 2; 113-122
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-7 z 7

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