http://dspace.nbuv.gov.ua:80/handle/123456789/114594 2026-04-17T11:45:48Z http://dspace.nbuv.gov.ua:80/handle/123456789/121625 Estimation of frequency characteristics of photodiode determined by motion of charge carriers in the space-charge region Danilyuk, A.I.; Dobrovolskiy, Yu.G. Frequency characteristics of photodiode determined by motion of charge carriers in the space-charge region was estimated. It was shown that the current in the external circuit depends on two functions (their specific kind) of coordinates of the electric field and generation density of photodetector current. 2006-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/121624 Simulation of multiwave pumped fiber Raman amplifiers Felinskyi, G.S.; Korotkov, P.A. The design model for development of optical fiber Raman amplifiers with the multiwavelength pumping scheme is proposed in this work. Our simulation based on the oscillator theory and spectroscopic model for the analysis of the Raman gain spectrum. Introducing the oscillatory lineshape functions gives the possibility for simple describing the wavelength dependence of Raman gain in optical fibers and it is very useful for the estimation of the gain bandwidth, Raman laser conditions, noise perfomance, and amplification processes in the Raman amplifiers. Modeling results are obtained without traditional solving the complicated system of coupled equations. The concept of an actual band based on the lineshape function is useful for the design of fiber Raman amplifiers with multiple wavelength pumping. Model validity is confirmed by the experimental measurements of amplified spontaneous emission in silica fiber. Proposed modeling allows us to analyze the fiber Raman amplifier with combined multiwavelength pumping source for the extension of amplification bandwidth to L-band, which has the broad bandwidth over 80 nm and low gain ripple less than 0.5 dB. The proposed spectroscopic model can be further extended for the analysis of the complex spontaneous Raman scattering spectra with other doping materials. 2006-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/121623 Growing the epitaxial undoped and N-doped ZnO films by radical beam gettering epitaxy Rogozin, I.V. Epitaxial undoped and N-doped ZnO films were obtained using the method of radical beam gettering epitaxy. Structural and luminescent properties of the obtained films were researched. In both cases, there can be seen orientation of the films along c-axis. In the spectrum of low-temperature photoluminescence of N-doped ZnO films, observed was a peak 3.31 eV probably of a neutral acceptor-bound exciton NO. The nature of donor-acceptor band 3.23 eV and green band 2.56 eV was discussed. 2006-01-01T00:00:00Z http://dspace.nbuv.gov.ua:80/handle/123456789/121622 Spin-dependent transport in magnetic sandwiches in the effective-mass approximation Los’, V.F.; Saltanov, V.N. A theory describing a spin-dependent transport of electrons through a thin metallic (or insulator) nonmagnetic layer sandwiched between two ferromagnets is developed in the ballistic regime and current-perpendicular-to-plane (CPP) geometry. The theory is based on the Landauer formalism and the transmission amplitude for the electron Bloch waves with an arbitrary dispersion law travelling from one ferromagnet to another through a nonmagnetic spacer (metallic or insulator). The semiclassical (non-oscillating) part of the magnetoresistance ratio for a metallic spacer is considered in the effective-mass approximation for the sandwich band structure. The parameters defining the value of the giant magnetoresistance (GMR) effect are obtained. It is shown that the electron specular scattering on the interfaces may be the cause for the CPP GMR effect. The influence of the electronic structure on the CPP GMR effect has been studied numerically in the effective-mass approximation. 2006-01-01T00:00:00Z