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Stimulated Raman scattering (SRS) in a long-distance fiber-optic communication line with wavelength-division multiplexing (WDM) is studied theoretically at a high power of the signal transmitted. A new criterion for determining the SRS threshold is used to calculate the critical input power versus the number of optical channels and frequency separation between them. The theoretical model is verified experimentally. SRS interaction between two channels in a communication line with an SRS amplifier for which the optical waveguide of the line serves as a nonlinear medium is measured. 相似文献
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I. Kh. Akopyan M. É. Labzovskaya B. V. Novikov V. M. Smirnov 《Physics of the Solid State》2007,49(7):1375-1381
The formation of the HgI2 crystalline phase in pores of various porous matrices and on their surfaces was studied. Based on the analysis of the evolution of the HgI2 optical spectra and electron and atomicforce microscopy data, it was shown that the formation of microcrystals of the stable red α modification is preceded by the formation and growth of particles of metastable yellow (β′) and orange modifications. The absorption edge of the β′ phase at T = 77 K is formed by excitonic transitions with an energy of ~2.7 eV. The Raman spectra of the β′ phase were compared to the spectra of known metastable yellow modifications. 相似文献
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Methods of optical metallography, scanning electron microscopy, and x-ray structural and spectral microanalyses are used to
investigate the structural features of porous titanium nickelide produced by the method of self-propagating high-temperature
synthesis (SHS) after its thermal treatment. It is demonstrated that the clearly expressed structural-phase inhomogeneity
observed in porous titanium nickelide after SHS is retained after thermal treatment. During thermal treatment with increase
in the annealing temperature, the volume fraction of the Ti2Ni phase enriched in titanium remains essentially unchanged; it is redistributed over the sample volume. The volume fraction
of the TiNi3 phase increases and nonuniformity in its density distribution over the sample volume, caused by the chemical inhomogeneity
of the matrix, is observed.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 86–92, October, 2008. 相似文献
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Na0.4Y0.6F2.2:Er3+ (NYF:Er3+) crystals with an Er concentration up to 15% were grown by the Bridgman-Stockbarger method. The luminescence kinetics was investigated for a series of NYF:Er3+ crystals (0.5–15% Er), as well as the concentration and temperature quenching of the luminescence from radiative Er levels upon selective laser excitation. It is shown that the luminescence from the 4S3/2 level is quenched significantly with increasing temperature and concentration. The luminescence from the 4G11/2, 2G(H)9/2, 4F9/2, and 4I9/2 levels is quenched mainly due to nonradiative multiphonon transitions. The concentration quenching of the luminescence from the 4I11/2 and 4I13/2 levels was not observed. Possible schemes of the self-quenching of excited levels of erbium are considered and the microparameters and macrorates of self-quenching are estimated by model quantum-mechanical calculation. Based on the comparison of the calculated and experimental self-quenching rates, the most probable mechanisms and schemes of self-quenching are determined. The self-quenching of the 4S3/2 level of erbium was investigated experimentally and theoretically. Good agreement is obtained between the experimental and the calculated kinetic curves and the dependences of the self-quenching rates on Er concentration. It is concluded that NYF:Er3+ crystals are promising as active media for tunable lasers with laser diode pumping. 相似文献
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Effect of a standing ultrasonic wave on the spontaneous and induced (specific, immune) processes of erythrocyte aggregation is studied in vitro on the basis of the data obtained from the elastic scattering of light. The effect of the time of ultrasonic action and the concentration of the initial reagents on the enhancement of these processes is analyzed. An approximate theoretical model is developed to describe the mechanism of the enhancement of erythrocyte aggregation by an ultrasonic field and the observation of the process of interest by the turbidimetric optical method. The model provides a good agreement between theory and experiment. The results of the study are used to derive recommendations as to how to increase the resolving power of the turbidimetric method of immunoanalysis with the aid of ultrasound. 相似文献
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A. M. Tkachuk S. É. Ivanova L. I. Isaenko A. P. Yelisseyev M. -F. Joubert Y. Guyot S. Payne 《Optics and Spectroscopy》2003,95(5):722-740
Optical spectra, intensities of radiative and nonradiative transitions, and luminescence kinetics in erbium-doped potassium-lead double chloride crystals KPb2Cl5:Er3+s(KPC:Er3+) were investigated. The crystals were grown by the Bridgman-Stockbarger method. Their absorption and luminescence spectra were studied experimentally. The crystal-matrix absorption edge was determined at 80 and 300 K. Intensity parameters, radiative transition probabilities, branching ratios, and nonradiative relaxation rates were estimated by the Judd-Ofelt method. The luminescence kinetics from the emitting levels 4 G 11/2, 2 G 9/2, 4 S 3/2, and 4 F 9/2 upon selective excitation was studied. 相似文献
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S. É. Ivanova A. M. Tkachuk M.-F. Joubert Y. Guiout S. Gui 《Optics and Spectroscopy》2000,89(4):535-548
Nd3+:Na0.4Y0.6F2.2 (Nd3+:NYF) crystals are grown by the Stockbarger–Bridgman method for a stoichiometric mixture prepared by the solid-phase method and containing neodymium up to 20 at. %. The absorption spectrum of Nd3+:NYF crystals exhibits bands located in the emission region of laser diodes. The peak absorption cross section of the 796.8-nm band is σ a = 0.96 × 10–20 cm2 and the bandwidth is Δλ = 17.5 nm. The most intense luminescence band is located at 1.05 μ m and the radiative time of the 4F3/2 level is τ0 = τexp ~ 960 μ s. It is shown that the 2P3/2 and 4D3/2 levels of Nd3+:NYF crystals are also radiative with lifetimes τ exp equal to ~110 and 9.5 μ s, respectively. However, these radiative transitions are partially quenched due to nonradiative relaxation. The intensity parameters Ω t are determined by the Judd–Ofelt method to be Ω2 = 1.18 × 10–20, Ω4 = 1.55 × 10–20, and Ω 6 = 2.85 × 10–20 cm 2. Using these parameters, the probabilities of radiative transitions and branching ratios are calculated, and the probabilities of nonradiative transitions are estimated. A conclusion is made that Nd3+:NYF crystals are promising as active media for diode-pumped tunable lasers, in particular, up-conversion-pumped lasers. 相似文献