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Wyświetlanie 1-15 z 29
Tytuł:
Physics of Solid-State Laser Materials
Autorzy:
Wojtowicz, A.
Powiązania:
https://bibliotekanauki.pl/articles/1888052.pdf
Data publikacji:
1991-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.55.Rz
78.50.-w
78.55.-m
Opis:
A survey of the physical properties of solid state materials activated with d$\text{}^{2}$, d$\text{}^{3}$ and d$\text{}^{8}$ transition metal ions is presented in the context of tunable laser operation. An emphasis is put on common characteristics of all three systems, like a strong electron-phonon coupling and similar electronic structures. The conditions necessary to obtain a tunable operation and to avoid an overlap of the excited state absorption and emission are formulated. It is shown that the d$\text{}^{3}$ configuration system has the largest range of allowed values of the crystal field parameter 10Dq.
Źródło:
Acta Physica Polonica A; 1991, 80, 2; 193-205
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stable LiF:F$\text{}_{2}^{+}$ Color Center Laser Oscillation at Room Temperature
Autorzy:
Tsuboi, T.
Powiązania:
https://bibliotekanauki.pl/articles/1992789.pdf
Data publikacji:
1998-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.55.Rz
78.55.Fv
Opis:
An LiF:F$\text{}_{2}^{+}$ color center laser using a two-mirror cavity is reported. The LiF:F$\text{}_{2}^{+}$ laser was achieved by creating the F$\text{}_{2}^{+}$ centers through the photoionization of the F$\text{}_{2}$ color centers at room temperature and simultaneously by exciting the F$\text{}_{2}^{+}$ centers optically. We obtained the F$\text{}_{2}^{+}$ broadband laser oscillation with a peak at 930 nm, and it was more powerful than the room-temperature broadband LiF:F$\text{}_{3}^{+}$ color center laser.
Źródło:
Acta Physica Polonica A; 1998, 94, 5-6; 773-778
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Wave Intensity Distributions in Complex Structures
Autorzy:
Tanner, G.
Chappell, D.
Maksimov, D.
Powiązania:
https://bibliotekanauki.pl/articles/1492500.pdf
Data publikacji:
2011-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.40.Dx
43.20.Dk
43.20.Rz
Opis:
The vibro-acoustic response of mechanical structures can in general be well approximated in terms of linear wave equations. Standard numerical solution methods comprise the finite or boundary element method in the low frequency regime and statistical energy analysis in the high-frequency limit. Major computational challenges are posed by the so-called mid-frequency problem - that is, composite structures where the local wavelength may vary by orders of magnitude across the components. Recently, a new approach towards determining the distribution of mechanical and acoustic wave energy in complex built-up structures improving on standard statistical energy analysis has been proposed. The technique interpolates between statistical energy analysis and ray tracing containing both these methods as limiting cases. The method has its origin in studying solutions of wave equation with an underlying chaotic ray-dynamics - often referred to as wave chaos. Within the new theory - dynamical energy analysis - statistical energy analysis is identified as a low resolution ray tracing algorithm and typical statistical energy analysis assumptions can be quantified in terms of the properties of the ray dynamics. We have furthermore developed a hybrid statistical energy analysis/finite element method based on random wave model assumptions for the short-wavelength components. This makes it possible to tackle mid-frequency problems under certain constraints on the geometry of the structure. Dynamical energy analysis and statistical energy analysis/finite element method calculations for a range of multi-component model systems will be presented. The results are compared with both statistical energy analysis results and finite element method as well as boundary element method calculations. Dynamical energy analysis emerges as a numerically efficient method for calculating mean wave intensities with a high degree of spatial resolution and capturing long range correlations in the ray dynamics.
Źródło:
Acta Physica Polonica A; 2011, 120, 6A; A-172-A-177
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Method of Jacobi Last Multiplier for Integrating Nonholonomic Systems
Autorzy:
Zhang, Y.
Powiązania:
https://bibliotekanauki.pl/articles/1493586.pdf
Data publikacji:
2011-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
45.20.Jj
02.30.Hq
02.30.Rz
Opis:
In this paper, a new integral method of nonholonomic dynamical systems is put forward. The differential equations of motion of nonholonomic systems in phase space are established. The definition of the Jacobi last multiplier of the systems is given, and the relation between the Jacobi last multiplier and the first integrals of the systems is discussed. The researches show that the solution of the systems can be found by the last multiplier if the quantity of first integrals of the systems is sufficient. An example is given to illustrate the application of the results.
Źródło:
Acta Physica Polonica A; 2011, 120, 3; 443-446
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Performance Analysis of WDM-FSO Link under Turbulence Channel
Autorzy:
Mazin, Ali A. Ali
Powiązania:
https://bibliotekanauki.pl/articles/1192036.pdf
Data publikacji:
2016
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
free space optics
BER
Atmospheric Turbulence
NRZ format
RZ technique
Opis:
In this paper, the performance analysis of FSO communication link in various atmospheric turbulence has been analysis for different bit rate using NRZ and RZ technique. The effect of turbulence on the link performance has been investigated by varying bit rate, turbulence strength and modulation format. FSO performance carried out for BER, Q. factor, received power under maximum link. Simulation results show that RZ format is best for strong turbulence. Where NRZ technique is used for low and medium turbulence.
Źródło:
World Scientific News; 2016, 50; 160-173
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Open End Correction for Arbitrary Mode Propagating in a Cylindrical Acoustic Waveguide
Autorzy:
Snakowska, A.
Jurkiewicz, J.
Smolik, D.
Powiązania:
https://bibliotekanauki.pl/articles/1493260.pdf
Data publikacji:
2011-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.20.Rz
43.20.Mv
Opis:
The paper presents a method of theoretical derivation and numerical calculation of the open-end correction coefficient for an arbitrary cut-on mode propagating in acoustic waveguide. Actually, the so-called open-end correction coefficient of acoustic tube, frequently discussed in literature, refers to specific conditions, when the wave heading the outlet is the plane wave. It follows from the fact that the plane wave is a commonly applied approximation when considering phenomena in duct-like devices or systems (tubes, musical instruments, heating or ventilation systems). The aim of the paper is to extend the concept of the open-end correction on the so-called higher Bessel modes, that under some conditions can also propagate in a duct. Theoretical results, forming the basis for numerical calculations, were obtained by considering diffraction at the duct end and applying the Wiener-Hopf factorization method. As a result, the formula for the acoustic field inside the duct was derived. For each Bessel mode present in the incident wave the reflected wave is composed of all cut-on modes of the same circumferential order. Each mode present in the reflected wave is characterized by the complex reflection/coupling coefficient, argument of which describes phase change at the duct end and therefore the open-end correction coefficient can be attributed to each coupled pair of modes.
Źródło:
Acta Physica Polonica A; 2011, 120, 4; 736-739
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nonlinear Upconversion-Rate in Er-Doped Fibers
Autorzy:
Jaskorzyńska, B.
Sergeyev, S.
Świłło, M.
Khoptyar, D.
Powiązania:
https://bibliotekanauki.pl/articles/2015114.pdf
Data publikacji:
2001-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Bh
78.55.-m
42.55.Rz
Opis:
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$\text{}_{2}$. However, recently published Monte Carlo simulations predict that the homogeneous upconversion rate is a nonlinear function of N$\text{}_{2}$ 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.
Źródło:
Acta Physica Polonica A; 2001, 99, 1; 147-153
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Generation of Intense Free-Electron Laser Radiation in the Terahertz Regime
Autorzy:
Pinhasi, Y.
Lurie, Y.
Pinhasi, G.
Friedman, A.
Powiązania:
https://bibliotekanauki.pl/articles/1401876.pdf
Data publikacji:
2015-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
41.60.Cr
52.59.Rz
Opis:
Free-electron lasers are high power radiation sources that utilize a distributed interaction between an accelerated electron beam and the electromagnetic field. In these devices, the electron beam serves as the amplification medium generating electromagnetic radiation, while propagating in a periodic magnetic structure called "wiggler" or "undulator". When electrons pass in the wiggler, they oscillate and act as a moving dipole emitting a wave packet of undulator synchrotron radiation. Incoherent summation of the wave packets results in a spontaneous emission. When the electrons are bunched into a short pulse, they all emit their wave packets in the same phase. The radiation wave packets combine coherently, resulting in super-radiance (where the energy radiated is proportional to the square of the electric charge). Such short bunches can be generated by an RF linear accelerator, driven by a photocathode injector. The radiation wavelength is determined by the velocity of the electrons and the spatial period of the undulator. The super-radiance mechanism enables the generation of intense radiation in frequency bands, whereas conventional sources fail to produce a powerful coherent radiation. In this article, we describe the design and analysis of ultrashort pulse free-electron laser operating at the sub-millimeter and terahertz regimes. The free-electron laser is based on a magnetostatic planar wiggler, in which super-radiant emission is emanated by accelerated electron bunches. A three-dimensional, space-frequency theory is developed in order to study radiation excitation in the wiggler. The total electromagnetic field (radiation and space-charge waves) is presented in the frequency domain as an expansion in terms of transverse eigenmodes of the (cold) cavity, in which the field is excited and propagates. The mutual interaction between the electron beam and the electromagnetic field is fully described by coupled equations, expressing the evolution of mode amplitudes and electron beam dynamics. The approach is applied in a numerical particle code WB3D, simulating wide-band interaction of a free-electron laser operating in the linear and non-linear regimes. The model is utilized to study spontaneous and super-radiant emissions radiated by an electron bunch at the sub-millimeter regime, taking into account three-dimensional space-charge effects emerging in such ultrashort bunches.
Źródło:
Acta Physica Polonica A; 2015, 128, 3; 315-318
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acoustic Impedance of Outlet of a Hard-Walled Unbaffled Cylindrical Duct for Multimode Incident Wave
Autorzy:
Jurkiewicz, J.
Snakowska, A.
Smolik, D.
Powiązania:
https://bibliotekanauki.pl/articles/1504427.pdf
Data publikacji:
2011-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.20.Mv
43.20.Rz
Opis:
In the paper, the specific acoustic impedance of outlet of an unbaffled duct for incident wave composed of one or many circumferential cut-on duct modes has been derived and presented on graphs. When considering the multimode excitation the equal energy per mode principle and random phases have been assumed. Experimentally verified assumption on equal energy per mode allows for quantitative analysis of the sound field and thus provides more physical insight into the in-duct and out-duct phenomena. The assumption of random phase was implemented by means of the Monte Carlo method and so the expected value, the standard deviation and the percentile curves of the impedance were presented. Numerical data obtained according to the derived theoretical formulae for single and multimode incident wave manifest strong modal character and dependence on the modes phases. The assumption of multimode incident wave has brought the theoretical model closer to what is being observed in practice, especially when ducts of large radius, such as heating and air conditioning systems or turbojet engines, are considered.
Źródło:
Acta Physica Polonica A; 2011, 119, 6A; 1061-1067
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Total Acoustic Power of Two Concentric Clamped Circular Plates Vibrating in a Fluid
Autorzy:
Rdzanek, W.
Powiązania:
https://bibliotekanauki.pl/articles/1402179.pdf
Data publikacji:
2015-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.20.Bi
43.20.El
43.20.Fn
43.20.Rz
Opis:
This study focuses on the problem of sound radiation by two concentric clamped flat plates, circular and annular, into the half-space. The system of three coupled differential equations comprising two equations of motions of plates and the wave equation, is solved exactly. Vibrations of plates are axisymmetric and time-harmonic with a single excitation frequency. The initial phase difference of excitations can be nonzero. Attenuation due to fluid loading and material damping is included. Kirchoff-Love and Kelvin-Voigt theories are applied. The effect of initial phase difference of excitations on the acoustic power radiated is examined as well as errors resulting from neglecting the fluid loading.
Źródło:
Acta Physica Polonica A; 2015, 128, 1A; A-41-A-45
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modeling of Passively Synchronized Dual Wavelength Q-Switched rm $Nd^{3+}:YVO_4$ Lasers
Autorzy:
Abdul Ghani, B.
Hammadi, M.
Powiązania:
https://bibliotekanauki.pl/articles/1419741.pdf
Data publikacji:
2012-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.55.Rz
42.60.Gd
87.19.lm
Opis:
A mathematical model describing the sum frequency generation of passively synchronized Q-switched pulses simultaneously emitted from two separate $Nd^{3+}:YVO_4$ lasers has been demonstrated. This model describes the temporal behavior of the output pulses, and studies the impact of the pumping energy variation on the characteristics of these pulses (output power, pulse separation, pulse widths, delay time). $V^{3+}:YAG$ and $Cr^{4+}:YAG$ saturable absorbers and a periodically poled KTP crystal are used to achieve and improve the synchronization of the emitted 1342 nm and 1064 nm wavelengths. The synchronization process generates pulsed yellow light with 593.5 nm wavelength, and it can be realized through adjusting the pumping energy of the gain media.
Źródło:
Acta Physica Polonica A; 2012, 122, 1; 103-108
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Asymptotic Formulae of the Modal Acoustic Impedance for the Asymmetric Vibrations of a Clamped Circular Plate
Autorzy:
Rdzanek, W.
Szemela, K.
Powiązania:
https://bibliotekanauki.pl/articles/1537549.pdf
Data publikacji:
2010-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.20.Ks
43.20.Rz
43.40.+s
Opis:
The asymptotic and approximate formulae for the asymmetric modal acoustic self- and mutual-impedance have been presented for a clamped circular plate embedded into a flat rigid baffle. The formulae have been obtained for the wide frequency band covering the low frequencies, the high frequencies and the middle frequencies. The high frequency asymptotics have been achieved using the method of contour integral and the method of stationary phase. The products of the Bessel and Neumann functions have been expressed as the asymptotic expansions. Further, the approximate formulae valid within the low and middle frequencies have been obtained from the high frequency asymptotics using some mathematical manipulations. The formulae presented are valid for both the axisymmetric vibrations and the asymmetric vibrations.
Źródło:
Acta Physica Polonica A; 2010, 118, 1; 141-154
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical Study of Diode Pumped Intracavity Doubled Passively Q-Switched Solid-State Lasers
Autorzy:
Alshikh Khalil, M.
Abbas, B.
Powiązania:
https://bibliotekanauki.pl/articles/1812353.pdf
Data publikacji:
2008-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.65.Ky
42.55.Rz
42.60.Gd
02.60.Cb
Opis:
In this paper, some designed curves such as peak power, energy, pulse width, and a factor describing the pulse symmetry are generated. With these curves and expressions, one can design a passively Q-switched intracavity frequency-doubled laser and predict the pulse characteristics.
Źródło:
Acta Physica Polonica A; 2008, 113, 6; 1639-1646
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modification of the Measurement Setup for Examination of Acoustic Field Distribution Inside Cylindrical Ducts for Axisymmetric Excitation
Autorzy:
Gorazd, Ł.
Jurkiewicz, J.
Raab, S.
Snakowska, A.
Powiązania:
https://bibliotekanauki.pl/articles/1400096.pdf
Data publikacji:
2013-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.20.Rz
43.20.Mv
Opis:
The aim of the paper is to present results of examination of the acoustic pressure field inside a model of a cylindrical duct. Measurements of the root mean square acoustic pressure were carried out using a new measurement setup, first in conditions allowing for propagation of the plane wave only, and next - by increasing the excitation frequency - with successive higher modes also taken in account. Two types of hard-walled cylindrical ducts were examined corresponding to mathematical models known as the infinite duct and the semi-infinite duct. A dedicated measurement setup is presented as well as the successive stages of its modification. In order to verify the modified measuring system, the first stage of the research work consisted in excitation of the axisymmetric modes only and assessing the degree of symmetry represented by the measurement data Significant improvement of the compatibility of the obtained measurement results with theoretical predictions was observed in the explored frequency band 800-5500 Hz that for the duct inside radius of a=0.077 m corresponded to the reduced frequency range 1.13
Źródło:
Acta Physica Polonica A; 2013, 123, 6; 1085-1089
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modeling the Dynamic Emission of a Polarized $Cr^{4+}:YAG$ Crystal Investigated by Double-Pulse Pumping Generated by a Nd-Laser
Autorzy:
Ghani, B.
Hammadi, M.
Powiązania:
https://bibliotekanauki.pl/articles/1808015.pdf
Data publikacji:
2009-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.55.Rz
42.50.-p
Opis:
A mathematical model describing the dynamic emission of intracavity polarized isotropic $Cr^{4+}:YAG$ solid-state saturable absorber was developed. This model considers double pumping laser pulses to simulate the actions of $Cr^{4+}:YAG$ as a dual Q-switched crystal (1.06 μm) and lasing medium (1.4 μm). The model describes the time evolution of interaction between the pumping laser pulse, partial polarizer and the polarized saturable absorber. The analysis of the polarization process is based on the assumption that at each moment of lasing evolution, the state of polarization represented by an eigenstate corresponds to the lowest radiation losses state. The model offers a simple mechanism for studying the kinetics of the pulsed lasers and the influence of the variations of the pumping laser power and nonlinear anisotropy parameter on the characteristics of the output laser pulses 1.06 μm and 1.4 μm. The angular rotation of the passive switch $Cr^{4+}:YAG$ reveals that the transmission of the polarized 1.06 μm laser radiation is strongly anisotropic in the saturation regime. The suggested model estimates the transmission of pumping laser density of the polarized light 1.06 μm radiation as a function of nonlinear anisotropy parameter, temporal behavior of the relative population inversion of Nd-laser, population inversion of the different polarized levels of $Cr^{4+}:YAG$ pulsed laser and the output laser pulse densities under impact of different values of the nonlinear anisotropy which is due to the self-induced anisotropy of its saturated absorption.
Źródło:
Acta Physica Polonica A; 2009, 115, 5; 873-879
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 29

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