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Wyświetlanie 1-15 z 170
Tytuł:
Dynamical Electro-Optical Characterization of Policryps Gratings
Autorzy:
Abbate, G.
Marino, A.
Vita, F.
Powiązania:
https://bibliotekanauki.pl/articles/2035667.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.70.Df
42.79.Kr
Opis:
We have studied the dynamical response at 633 and 1550 nm of a new polymer-liquid crystal composite, realized in a form of a thick grating. This composite is known as Policryps, an acronym that stands for "Polymer Liquid Crystals Polymer Slides", because it shows a sequence of polymeric sheets alternated by layers containing only liquid crystal. Policryps gratings can be electrically switched between diffracting and non-diffracting states with a good diffraction efficiency in the visible region. After optimization of their performances, including response time, in the near infrared region, they can be conveniently proposed as a key component in photonic devices for telecom applications. Our results show very interesting response times ranging from 1 to 3 ms (switching on) and from 0.1 to 0.4 ms (switching off). Furthermore, switching ON times appear to be ruled by two different physical mechanisms with characteristic times differing by one order of magnitude. A deeper insight of these mechanisms might lead to response times, all in the submillisecond range.
Źródło:
Acta Physica Polonica A; 2003, 103, 2-3; 177-186
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical and Electrical Characterization of (002)-Preferentially Oriented n-ZnO/p-Si Heterostructure
Autorzy:
Abdallah, B.
Al-Khawaja, S.
Powiązania:
https://bibliotekanauki.pl/articles/1401869.pdf
Data publikacji:
2015-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
47.15.gm
66.70.Df
68.60.-p
Opis:
In this paper, preferentially oriented (002) ZnO thin films have been grown on Si (100) and glass substrates using radio frequency magnetron sputtering. The dependence of the quality of the ZnO thin films at different substrate temperatures on the growth is studied. A ZnO thin film with c-axis-oriented würtzite structure is obtained at a growth temperature from 200 to 400°C. X-ray diffraction shows that the full width at half maximum θ -2θ of (002) ZnO/Si is located at approximately 34.42°, which is used to infer the grain size that is found to be 17 nm to 19.7 nm. The FWHM is 9.5° to 8° in rocking curve mode, from which the crystalline quality has been determined. The texture degree demonstrates the improvement in quality with the increase of substrate temperature, which is best at 400°C. The band gap extracted by UV transmittance spectrum has been identified as 3.2 eV at 400°C. The electrical characteristics via C-V and I-V measurements on the basis of the heterojunction thermal emission model confirm the domination of high-density grain boundary layer existing at the interface. The transport currents indicate to the presence of space-charge-limited current and trap-charge-limited current mechanisms.
Źródło:
Acta Physica Polonica A; 2015, 128, 3; 283-288
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Biomedical Optical Applications of Liquid Crystal Devices
Autorzy:
Abdulhalim, I.
Moses, R.
Sharon, R.
Powiązania:
https://bibliotekanauki.pl/articles/1814044.pdf
Data publikacji:
2007-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.30.Va
42.70.Df
42.81.Gs
Opis:
Liquid crystals exhibit large electro-optic effects which make them useful for a variety of applications as fast, compact, and tunable spectral filters, phase modulators, polarization controllers, and optical shutters. They were largely developed for liquid crystal displays and in the last decade for optical telecommunications, however their application in the field of optical imaging just started to emerge. These devices can be miniaturized thus have a great potential useful in miniature optical imaging systems for biomedical applications. Using a collection of tunable phase retarders one can perform: 1. Stokes parameters imaging for skin and eye polarimetric imaging; 2. Tunable filtering to be used for hyperspectral imaging, fluorescence microscopy, and frequency domain optical coherence tomography; 3. Adaptive optical imaging and eye aberrations correction; 4. Phase shift interferometric imaging; 5. Variable frequency structured illumination microscopy. Basic optics of liquid crystals devices is reviewed and some novel designs are presented in more detail when combined to imaging systems for a number of applications in biomedical imaging and sensing.
Źródło:
Acta Physica Polonica A; 2007, 112, 5; 715-722
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Discrete Space-Time by Means of the Weyl-Dirac Theory
Autorzy:
Agop, M.
Chicos, L.
Gîrţu, M.
Powiązania:
https://bibliotekanauki.pl/articles/2047353.pdf
Data publikacji:
2007-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
04.20.Cv
05.45.Df
Opis:
A connection between the Weyl-Dirac theory and scale relativity theory through the hydrodynamic models (relativistic and non-relativistic approaches) is established. In such conjecture, considering that the motions of the microparticles take place on continuous but non-differentiable curves i.e. on fractals, a Weyl-Dirac type equation was found. Some correspondences with known hydrodynamic models, particularly Białynicki-Birula's approach, are analyzed. All these results reflect the fractal structure of the space-time (a concept in agreement with the new ideas on the space-time)
Źródło:
Acta Physica Polonica A; 2007, 112, 1; 3-12
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Some Aspects Concerning the "Memorization Effect" in Complex Fluid
Autorzy:
Agop, M.
Ochiuz, L.
Timofte, D.
Barlescu, V.
Danila, M.
Gheorghita, L.
Paun, V.
Solovastru, L.
Popa, C.
Powiązania:
https://bibliotekanauki.pl/articles/1204873.pdf
Data publikacji:
2014-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.45.Df
47.53.+n
03.65.-w
Opis:
In the frame of a non-standard scale relativity model, the specific momentum, states density and internal energy conservations laws are obtained. The chaoticity, either through turbulence in the fractal hydrodynamics approach, or through stochasticization in the Schrödinger type approach, is generated only by the non-differentiability of the movement trajectories of the complex fluid entities. Using the conservation laws mentioned above, by numerical simulations, hysteretic type effects (dynamics of hysteretic cycles) occur.
Źródło:
Acta Physica Polonica A; 2014, 126, 3; 663-669
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Wave-Particle Duality through a Hydrodynamic Model of the Fractal Space-Time Theory
Autorzy:
Agop, M.
Nica, P.
Harabagiu, A.
Powiązania:
https://bibliotekanauki.pl/articles/1812346.pdf
Data publikacji:
2008-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.45.Df
47.53.+n
03.65.-w
Opis:
Considering that the microparticle movements take place on fractal curves, the wave-particle duality is studied in the fractal space-time theory (scale relativity theory). The Nottale model was extended by assuming arbitrary fractal dimension, $D_F$, of the fractal curves and third-order terms in the equation of motion of a complex speed field. It results that, in a fractal fluid, the convection, dissipation, and dispersion are reciprocally compensating at any scale (differentiable or non-differentiable), whereas a generalized Schrödinger equation is obtained for an irrotational movement of the fractal fluid. The absence of the dispersion implies a generalized Navier-Stokes type equation and the usual Schrödinger equation results for the irrotational movement in $D_F$=2 of the fractal fluid. The absence of dissipation implies a generalized Korteweg-de Vries type equation. In such conjecture, the duality is analyzed through a hydrodynamic formulation. At the differentiable scale, the duality is achieved by the flowing regimes of the fractal fluid, while at the non-differentiable scale, a fractal potential controls, through the coherence, the duality.
Źródło:
Acta Physica Polonica A; 2008, 113, 6; 1571-1588
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Annealing Temperature on $Y_2O_3:SiO_2$ Nanocomposite Prepared by Sol-Gel Process
Autorzy:
Ahlawat, R.
Aghamkar, P.
Powiązania:
https://bibliotekanauki.pl/articles/1205213.pdf
Data publikacji:
2014-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.46.Bc
61.46.Df
78.67.Bf
Opis:
Oxide nanoparticles embedded in a polymer matrix produce nanocomposites which are useful for optics and electronic applications. Yttrium oxide nanoparticles have received much attention due to their various properties and are significantly used in fundamental and application oriented fields. The present paper reports the influence of annealing temperature on the $Y_2O_3:SiO_2$ nanocomposite prepared by sol-gel process. $Y(NO_3)_3 ·4H_2O$ and tetraethoxysilane were used as precursors and obtained powdered form of $Y_2O_3:SiO_2$ composite. The powder sample was annealed at 500C and 900C for 6 h which were characterized by X-ray diffraction, Fourier transform infrared and transmission electron microscope. X-ray diffraction data described that the broadening of peaks decreases with increase in annealing temperature which may be due to the increase in particle size. Sample analyzed by Fourier transform infrared and transmission electron microscopy confirmed the grain size dependence on annealing temperature. Cubic phase of yttrium oxide crystal structure was obtained within the silica matrix. The nanocrystallites size has been calculated using Debye-Scherrer formula, Williamson-Hall plot and transmission electron micrographs and compared at two different temperatures (a) 500C and (b) 900C.
Źródło:
Acta Physica Polonica A; 2014, 126, 3; 736-739
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synthesis, Separation and Electrical Properties of $WO_{3-x}$ Nanopowders via Partial Pressure High Energy Ball-Milling
Autorzy:
Al Mohammad, A.
Powiązania:
https://bibliotekanauki.pl/articles/1807792.pdf
Data publikacji:
2009-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.Ev
61.46.Df
64.60.Cn
Opis:
Reduction processes of $WO_{3}$ nanopowder either with carbon or with hydrogen were observed using X-ray powder diffraction and transmission electron microscope. The phase transformations, separation, grain size and electrical conductivity of $WO_{3-x}$ nanopowder during reductions via partial pressure high energy ball-milling have been studied. During the carbon-reduction process the monoclinic $WO_{3}$ structure transforms to nonstoichiometric Magneli phases $W_{40}O_{118}$, $WO_{2.9}$ and finally to $WO_{2}$ and W mixed phases. The Magneli $WO_{3-x}$ phases exhibit specific fringe contrast imaging of well-ordered crystallographic shear planes. In comparison, the monoclinic $WO_{3}$ structure transforms to hydrate $WO_{3}·1/3H_{2}O$, hexagonal $WO_{3}$, non-stoichiometric $WO_{2.7}$ and finally to $WO_{2}$ and W mixed phases during the hydrogen-reduction process. The inclusion of hydrogen atoms between the $WO_{6}$ octahedral structure shifts the reduction steps to lower milling times. It demonstrates that the formation of hydrate $WO_{3}$ phases enhances the amenability of the system to reduction. The activation energy for conduction was deduced from the Arrhenius equation and was found to depend on oxygen partial pressure or presence of the hydrogen atoms. The defect band model was used for interpretation of these behaviors. It supposes that the surface oxygen vacancies introduce donor levels in the gap of semiconductor, so free electrons are produced by reduction.
Źródło:
Acta Physica Polonica A; 2009, 116, 2; 240-244
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Annealed (0001) α-$Al_2O_3$ Surfaces on Heteroepitaxial Growth of Silver Nanoparticles
Autorzy:
Al-Mohammad, A.
Powiązania:
https://bibliotekanauki.pl/articles/1808108.pdf
Data publikacji:
2009-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.55.-a
81.15.Aa
61.05.jh
61.46.Df
Opis:
The effect of annealed (0001) α -$Al_2O_3$ surfaces on heteroepitaxial growth of silver nanoparticles were analysed by reflection high-energy electron diffraction, transmission electron microscope and selected area electron diffraction. Ag nanoparticles were deposited on 1× 1 stoichiometric and reconstructed (111)Al//(0001) α -$Al_2O_3$ with the Knudsen cell. The maximum cluster density method and the Lifethenz theory of Van der Waals energy were used to investigate the Ag//(0001)α -$Al_2O_3$ interface parameters. The growth modes, lattice parameters, nanoparticle forms and sizes are strongly dependent on the substrate surface structures. Initially, three-dimensional islands of Ag nanoparticles grow on both kinds of surfaces with partial hexagonal shapes. Ag nanoparticles on stoichiometric surface create the (111)Ag//(0001)α -$Al_2O_3$ interface without any preferred epitaxial direction. On this surface, Gaussian distribution is characteristic of an atom-by-atom growth mode with density of Ag nanoparticles lower than saturation density while a coalescence growth mode appears due to binary collisions between Ag nanoparticles accompanied by a liquid-like behaviour after saturation density. In case of reconstruction substrates, the epitaxial relationships between Ag nanoparticles and the surface are formed (111)Ag//(0001)α -$Al_2O_3$, 〈01\bar(1)〉Ag//[12\bar(3)0]α -$Al_2O_3$ or 〈01\bar(1)〉Ag//[1\bar(1)00]α-$Al_2O_3$. The Ag nanoparticles make rotation with angles between ± 6° around the epitaxial orientations 〈1\bar(1)00〉 or 〈12\bar(3)0〉. Only the atom-by-atom growth mode were found at all Ag nanoparticles growth processes.
Źródło:
Acta Physica Polonica A; 2009, 115, 3; 679-684
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
ZnO Nanopowders as Chemical Sensor to Malathion Vapor
Autorzy:
Al-Mohammad, A.
Darwich, R.
Rukiah, M.
Abo Shaker, S.
Kakhia, M.
Powiązania:
https://bibliotekanauki.pl/articles/1195948.pdf
Data publikacji:
2014-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.16.Be
84.37.+q
81.20.Ev
81.20.Wk
07.07.Df
Opis:
Thick films of zinc oxide (ZnO) nanopowders have been prepared by high energy ball-milling for various spans of mill time (3-18 h). The morphology and crystal structure of the prepared ZnO powder were characterized by scanning electron microscope and X-ray diffraction. The ZnO thick films were then used to construct a gas sensor for O,O-dimethyl dithiophosphate of diethyl mercaptosuccinate (malathion) at different operating temperatures. The sensor response at 100 ppm of malathion was found to reach a maximum as large as 80 at 6 h of high energy ball-milling, four times larger than that found for ethanol. Scanning electron microscope observation of the granular state and pore size distribution analyses indicated that increasing high energy ball-milling time gave rise especially to an increase in the volume of pores in the pore size range of 6-35 nm. It is suggested that such a change in nanostructure is responsible for the marked promotion of the response to malathion.
Źródło:
Acta Physica Polonica A; 2014, 125, 1; 131-134
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of second harmonic generation in KDP/Al₂O₃ crystalline nanocomposite
Autorzy:
Andrushchak, N.
Kulyk, B.
Göring, P.
Andrushchak, A.
Sahraoui, B.
Powiązania:
https://bibliotekanauki.pl/articles/1052895.pdf
Data publikacji:
2018-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.Bc
61.46.Df
68.37.Ps
42.65.Ky
Opis:
Crystalline nanocomposite KDP/Al₂O₃ was obtained by growth of KDP nanocrystals inside nanopores of amorphous alumina matrix (Al₂O₃) with pores diameter of 35 nm. Performed atomic force microscopy and X-ray diffraction analysis confirmed that Al₂O₃ matrix is filled up with a tetragonal phase KDP nanocrystals in preferred crystallographic orientation [100]. The nonlinear optical response was studied by means of second harmonic generation via the Maker fringe technique employing picosecond laser pulses at wavelength of 1064 nm. The polarization dependent second harmonic generation response was observed mainly due to the macroscopic crystalline structure anisotropy of KDP/Al₂O₃ nanocomposite. The investigation of such type of nanocomposites which combine nanoscale nonlinear optical materials has a great importance since they may improve the performance of entire system.
Źródło:
Acta Physica Polonica A; 2018, 133, 4; 856-859
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spatial Optical Solitons in Bulk Nematic Liquid Crystals
Autorzy:
Assanto, G.
Peccianti, M.
Conti, C.
Powiązania:
https://bibliotekanauki.pl/articles/2035665.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.70.Df
42.65.Tg
Opis:
We present an overview of our recent experimental results on two-dimensional optical spatial solitons in voltage biased planar cells with nematic liquid crystals. Excitation, induced waveguiding, and interactions are illustrated and interpreted in terms of the inherent re-orientational, non-resonant and nonlocal nonlinear response.
Źródło:
Acta Physica Polonica A; 2003, 103, 2-3; 161-167
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lattice Thermal Conductivity of GaAs
Autorzy:
Ataullah Ansari, M.
Ashokan, V.
Indu, B.
Kumar, R.
Powiązania:
https://bibliotekanauki.pl/articles/1489863.pdf
Data publikacji:
2012-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.kd
66.70.Df
63.22.Rc
63.20.Ry
Opis:
A new approach to evaluate the relaxation times of various collision events responsible for thermal transport has been reported through which various deficiencies of earlier models of lattice thermal conductivity have been resolved. These investigations involve the evaluation of the phonon Green functions via a non-perturbative approach. The new expressions of relaxation times expressions for scattering of phonons by boundaries, atomic impurities, phonon-phonon scattering, electron-phonon scattering are the new features of the theory. The lattice thermal conductivity of three samples of GaAs has been analyzed on the basis of modified Callaway model and fairly good agreement between theory and experimental observations has been reported.
Źródło:
Acta Physica Polonica A; 2012, 121, 3; 639-646
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Enhancement of Refractive Index Sensitivity in Photonic Crystal Waveguide-Based Sensors by Selective Infiltration
Autorzy:
Bagci, F.
Akaoglu, B.
Powiązania:
https://bibliotekanauki.pl/articles/1399501.pdf
Data publikacji:
2013-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.70.Qs
78.67.Pt
07.07.Df
42.79.-e
Opis:
We present a liquid refractive index sensor based on a photonic crystal waveguide slab structure. Sensing mechanism employed in this study is based on the shift in cut-off wavelength as the lattice holes are selectively infiltrated. Three-dimensional plane-wave expansion and finite-difference time-domain methods are used to determine the band structure and transmission spectra, respectively. First, the sensitivity of the device is analyzed for the structure where only the first rows of holes adjacent to the line-defect are infiltrated. In addition, this analysis is repeated for a range of hole diameters. Second, the effects of infiltrated holes which are placed in the line-defect are investigated. As these infiltrated central holes are introduced, the proposed device exhibits 5.3 times improved sensitivity.
Źródło:
Acta Physica Polonica A; 2013, 124, 1; 50-55
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of External Electric Field on Time of Nonlinear Optical Reorientational Effect in Nematics
Autorzy:
Bajdecki, W. K.
Karpierz, M. A.
Powiązania:
https://bibliotekanauki.pl/articles/2035684.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.65.-k
42.70.Df
Opis:
Nonlinear reorientation phenomena in nematic liquid crystals cause extremely large refractive index changes. However, this effect is relatively slow and the determination of the time necessary to appearing or disappearing of the nonlinear effect is an important issue. In this work we present measurements of the time of increasing the nematics reorientation induced by the light beam passing through the liquid crystalline layer. The influence of external low-frequency electric field suppressing reorientation is also reported. The obtained results describing relations between time and optical power of light as well as between time and external electric field intensity are in good agreement with theory.
Źródło:
Acta Physica Polonica A; 2003, 103, 2-3; 187-193
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 170

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