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The possibilities of LiNbO3-Ho3+ crystals for optical cooling based on the anti-Stokes luminescence in the wavelength range 2000-2200 nm are investigated. The efficiency and cooling temperature under the continuous wave (CW) excitation at the wavelengths 2035-2071 nm by ~100 W power are estimated. It is shown that under the CW excitation at 2035 nm wavelength the maximum cooling temperature is equal...
The possibility of creating free electron lasers without inversion (FELWI) is shown to have threshold character with respect to the intensity of wave to be amplified. A description of threshold conditions is given in the single-particle approach. It is shown that as the observation threshold of amplification without inversion is rather high, and the possibility of experimental realization of FELWI...
The dynamics ofatomic populations in the field of a single femtosecond pulse is numerically investigated in the frameworks of the resonant approximation and beyond it. It is shown that for the pulses with the extremely short duration the violation of resonant approximation leads not only to the quantitative but also to the qualitative changes in the behavior of the three-level atom.
It was shown that at the dynamical diffraction of spherical X-ray wave on a short period superlattice, a focusing of satellites occurred both at different depths of the superlattice and at different distances from the crystal in vacuum depending on the structural factors of the superlattice. Based on the obtained results a method for investigation of a superlattice by means of dynamical diffraction...
Several modem methods of nanowires fabrication and their characterization are presented and discussed. Electronic and thermal transport measurement techniques ofnanowire arrays as well as of an individual nanowire in the wide temperature range are presented.
The photoelectric characteristics of transparent ZnO films have been investigated. The possibility of controlling the conductivity by the introduction of impurities is presented. The ratio of conductivities of the films doped with donor and acceptor impurities reaches value of 109. It is shown that it is possible to achieve a significant increase in the ratio of photoconductivity to the dark conductivity...
A new scheme for the efficient generation of broadband terahertz radiation via optical rectification of femtosecond laser pulses in the single-domain lithium niobate crystal equipped with the step-wise phase mask (SPM) is investigated. It is shown that using the SPM one can provide the phase matching for all the spectral components of a terahertz pulse by providing the effective conversion of laser...
An advantage of implementation of object-oriented programming principles in numerical simulation in hard X-ray optics was considered. The suggested approach was demonstrated on the example of two-beam X-ray interferometer with the refracting prism. It was shown that the proposed coding technique significantly simplifies the main program code by reducing its size, as well as making it more readable...
The results ofmeasurements on the search for the cluster decay of 252Cfnucleus with the emission ofthe bound state of eight neutrons are presented. The value of an upper limit ofthe partial probabilities for this process is obtained, which contradicts to the results ofthe recently published work, in which the possible existence of octaneutron was declared. Based on the results of our measurements,...
The spectra of two photon generation in the process of spontaneous parametric down conversion are studied in a waveguide containing the nonlinear segments with the spatial chirp. Three photon parametric interaction is investigated for the waveguide containing only a spatial fundamental mode. The peculiarities of spectra broadening of photon pair in the chirped waveguide are studied.
The Laue-Bragg diffraction from monolithic crystal systems was realized. It was shown that a multiple increase in the number ofreflections leads to a supercollimation ofthe beam. A precision method for measuring the reflection coefficients is proposed, in which this beam is used as the primary one.
Intra-subband transitions caused by light absorption in a parabolic quantum well is considered taking into account the scattering by ionized impurity centers. To calculate the scattering matrix element, the Born approximation is used and the interaction with the impurity is described by the Coulomb potential. An analytical expression for the absorption coefficient of processes with the initial absorption...
Expressions for estimation of the thermal linear expansion coefficients and of the thermal conductivities of amorphous dielectrics above the Debye temperature are obtained. It is shown that for the compounds of the chemical composition corresponding to the rare-earth magnesium hexaaluminates taken as an example these parameters for amorphous compounds are less than for polycrystalline.
The X-ray interferometric Fresnel holography was proposed and theoretically investigated. It was shown that under definite conditions the recorded interference pattern formed at the output surface ofthe analyzer crystal (the third block of interferometer) is the X-ray interferometric hologram (generally the Fresnel one) of the object under investigation. Further reconstruction of an image is performed...
Within the frameworks of generalized model of polypeptide chain (GMPC) the concentrational behavior of helix-coil transition temperature of biopolymer in two-component solvent was observed on the simplest models. It is shown that if the solvent and the ligand interact with the biopolymer at different binding sites, and even if both components influence the helical state in the same way, the model...
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