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A.H. Reshak G. Lakshminarayana V.G. Yushanin M. Chmiel M.G. Brik 《Optics Communications》2010,283(15):3049-3051
We have observed a several times enhancement of the optical second harmonic generation in newly synthesized Europium doped PbO-Bi2O3-Ga2O3-BaO glasses for the fundamental wavelength 1320 nm during optical treatment by coherent fundamental and doubled frequency beams with a pulse duration about 15 ns. We have found that the maximal optical second harmonic generation was achieved for the Eu content of about 1.4% at fundamental beam average power equal to about 3 GW/cm2 , temperature of about 300 K and intensity ratio between the fundamental and doubled frequency beams of about 9. Frequency repetition of the optical pulses was equal to about 10 Hz. It was shown that doping by other rare earth ions, particularly by Dysprosium does not give a sufficient contribution to the effect. 相似文献
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Y. Benmimoun A. Bouhemadou R. Khenata A. H. Reshak B. Amrani M. Ameri H. Baltache 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):165-171
The results of first-principles theoretical study of the structural,
electronic and optical properties of SrCl2 in its cubic structure, have
been performed using the full-potential linear augmented plane-wave method
plus local orbitals (FP-APW+lo) as implemented in the WIEN2k code. In this
approach both the local density approximation (LDA) and the generalized
gradient approximation (GGA) are used for the exchange-correlation (XC)
potential. Also we have used the Engel-Vosko GGA formalism, which optimizes
the corresponding potential for band structure calculations. We performed
these calculations with and without spin-orbit interactions. Including
spin-orbit coupling cause to lifts the triple degeneracy at Γ point
and a double degeneracy at X point. Results are given for structural
properties. The pressure dependence of elastic constants and band gaps are
investigated. The dielectric function, reflectivity spectra and refractive
index are calculated up to 30 eV. Also we calculated the pressure and volume
dependence of the static optical dielectric constant. 相似文献
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I. Fuks-Janczarek Jean Ebothe R. Miedziński R. Gabański A. H. Reshak M. Łapkowski R. Motyka I. V. Kityk J. Suwiński 《Laser Physics》2008,18(9):1056-1069
A new promising organic chromophore for two-photon laser absorption at 1064 nm with 1,4-diethoxy-2,5-bis[2-(5-methylthien-2-yl)ethenyl]benzene (A-C) was synthesized. We have performed evaluations of the two-photon absorption for these chromophores incorporated into the polymer matrices. Following the obtained quantum chemical data, we have performed quantum chemical simulations of the third-order susceptibilities for the investigated chrompophore incorporated into the PMMA matrices. The calculations were done within the three-level model. We have established that the experimentally calculated data are a bit less than theoretically calculated; however, the general tendency of their changes shows a good coincidence. The maximally achieved value of the TPA is equal to about 59.2 cm/GW at wavelength 1064 nm, which, together with their high photothermal stabilities, make them good candidates for optical-limiting processes. 相似文献
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B. Claudet K. Michalska-Małecka K. Pluciński P. Mandracci A. H. Reshak 《Laser Physics》2008,18(8):999-1002
A correlation between the resistivity-voltage dependences of the hydrogenated SiN/Si(111) films and the photo-induced third-harmonic generation (PITHG) at λ = 1064 nm in the reflected light regime was found. The contribution to the PITHG is both due to linear photo-induced surface changes as well as due to the hydrogen dopants. When the fundamental power density increases to higher than 1.2 GW/cm2, there occurs a drastic decrease of the PITHG. Maximal PITHG changes are observed at a pump-probe delay time about 18 ps and the value of the PITHG slightly increases with the enhanced applied dc-electric field during illumination by a third-harmonic laser beam as a photo-inducing one. The deviation from the tripled frequency wavelength to higher wavelengths substantially suppresses the output PITHG signal. The crucial role of the interface trapping levels and silicon-hydrogen charge transfer is shown. 相似文献
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The optical properties of the SrFX (X=Cl, Br, I) compound have been reported using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the WIEN2K code. We employed the generalized gradient approximation (GGA), which is based on exchange-correlation energy optimization to calculate the total energy. Also we have used the Engel-Vosko GGA formalism, which optimizes the corresponding potential for band structure calculations. Our calculations show that the valence band maximum (VBM) and conduction band minimum (CBM) are located at Γ resulting in a direct energy gap. We present calculations of the frequency-dependent complex dielectric function ε(ω) and its zero-frequency limit ε1(0). We find that the value of ε1(0) increases on decreasing the energy gap. The reflectivity spectra and absorption coefficient have been calculated and compared with the available experimental data. 相似文献
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The linear and nonlinear optical susceptibilities for different tensor components of BaBiBO4 single crystals have been calculated using the full-potential linear augmented plane wave method. The results of these calculations are verified by our measurements of linear and nonlinear optical properties using Nd-YAG laser at fundamental wavelength 1064 nm. The calculated energy gap is in a good agreement with experimental energy gap data obtained by optical absorption. We present results for the imaginary and real parts of the frequency-dependent dielectric constant. The calculated birefringence of BaBiBO4 is positive in agreement with the experimental data. Calculations are reported for the frequency-dependent complex part of second-order nonlinear optical susceptibilities . The linear and nonlinear optical susceptibilities are scissors corrected to match the value of the energy gap from the local density approximation calculations with the experimental value. The second harmonic generation efficiency of this compound is about five times larger than KDP (KH2PO4). It is crucial that we have obtained a large anisotropy of the second-order susceptibilities for three main second-order tensor components both experimentally and theoretically. The possible origin of the obtained anisotropy is discussed within a framework of the energy band calculations. 相似文献