Temat: group velocity dispersion - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Control of the effects of crystal dispersion at different orders in the mixing of three phase-matched waves on a 5- to 100-fs time scale
Autorzy:: Andreoni, A.
Bondani, M.
Potenza, M.A.C.
Powiązania:: https://bibliotekanauki.pl/articles/308723.pdf
Data publikacji:: 2000
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Tematy:: three-wave mixing
ultra-broadband phase-matching
beta-barium borate
group velocity matching
group velocity dispersion
Opis:: A number of manners to obtain first-order achromatic phase matching of both type I and type II are presented and the most advantageous ones are identified to generate high-spectral quality 100-fs pulses by either parametric generation or frequency up-conversion. In the case of frequency-doubling high-energy 5-fs Ti: sapphire pulses, a non-collinear phase-matching I geometry in a beta-barium borate crystal cut at 44 deg is devised that should allow high conversion efficiency, virtually without pulse lengthening and intra-pulse frequency chirp due to group-velocity dispersion.
Źródło:: Journal of Telecommunications and Information Technology; 2000, 1-2; 16-19
1509-4553
1899-8852
Pojawia się w:: Journal of Telecommunications and Information Technology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Properties of low frequency TE-electromagnetic wave in ternary plasma photonic crystal
Autorzy:: Dehnavi, Z. N.
Askari, H. R.
Malekshahi, M.
Dorranian, D.
Powiązania:: https://bibliotekanauki.pl/articles/174815.pdf
Data publikacji:: 2017
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:: plasma photonic crystal
effective plasma frequency
photonic band gap
dispersion relation
group velocity
reflectivity
Opis:: In this study, the oblique incident of the electromagnetic waves with frequencies lower than plasma frequency in one dimensional ternary plasma photonic crystal has been investigated. The unit cell of crystal contains a plasma layer that is embedded in two different dielectric layers. Using the wave equation, Bloch theory, and boundary condition, the dispersion relation, the group velocity and the reflection relation of the structure have been obtained. Numerical results are presented in the form of dispersion curves. The dependence of photonic band gap characteristics on plasma frequency is discussed. One attempt has been made to show how the photonic band gap characteristic of a particular structure changes when the dielectric material of the unit cell is replaced by other dielectric materials or when the incident angle of the electromagnetic wave is changed. Results show that plasma layer characteristics has a significant effect on band gaps and wave propagation characteristics; also the results show that the proposed multi-layered structure can act as a tunable photonic crystal which can be controlled by the external parameters.
Źródło:: Optica Applicata; 2017, 47, 3; 457-470
0078-5466
1899-7015
Pojawia się w:: Optica Applicata
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Analytical and numerical identification of lamb waves modes for hybrid composites
Autorzy:: Barski, M.
Pająk, P.
Powiązania:: https://bibliotekanauki.pl/articles/245066.pdf
Data publikacji:: 2017
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: structural health monitoring
elastic waves
dispersion curve
stiffness matrix method
numerical simulations
finite element method
group velocity
fale sprężyste
krzywa dyspersji
symulacje numeryczne
metoda elementów skończonych
prędkość grupowa
Opis:: The current work is devoted to the problem of analytical and numerical identification of fundamental elastic waves' modes, namely symmetric mode S0 and antisymmetric mode A0, in the case of hybrid composite. The investigated material consists of one layer made of aluminum alloy Pa38 and six layers made of glass fabric/epoxy resin. At the very beginning, the dispersion curves are determined with the use of stiffness matrix method. The calculated values of phase velocities are verified by numerical simulation. The semi – analytical finite element method is applied. Next, the numerical simulations of elastic waves propagation are performed. In the studied model, the plane state of strain is assumed. These simulations are carried out with the use of finite element method. The excitation signal is a sine wave modulated by Hanning window. The simulation is repeated for different excitation frequency. The group velocities of wave modes S0 and A0 are estimated and compared with the analytical results. The evaluation of the group velocities is based on the analysis of the appropriate components of displacement. The two different method are employed, namely: cross – correlation method and envelope extraction by Hilbert transform. Generally, the obtained results are in a good agreement. However, the method based on envelope extraction by Hilbert transform provides better correlation between analytical and numerical results. The significant discrepancy is observed in the case of symmetric mode S0 for relatively high values of frequency. It is caused by the dispersion phenomena. The analytical calculations are performed with the use of SCILAB 5.5.2 free software and the numerical simulations are carried out with the use of finite element system ANSYS 13.0.
Źródło:: Journal of KONES; 2017, 24, 1; 31-38
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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