V. V. Osiko

Raman spectroscopy of crystals for stimulated Raman scattering

Abstract Raman frequency shift, line width, integral and peak Raman scattering cross sections were measured in various crystals using spontaneous Raman spectroscopy. The highest Raman gain coefficient in steady state Stimulated Raman Scattering (SRS) regime was proved to be in barium nitrate crystal; for transient SRS it is expected to be in lithium niobate and tungstate crystals. Barium molybdate crystal is proposed as a new highly efficient Raman material. OCIS : 300.6450; 290.5910; 190.2640

SrWO4 :Nd3+: new material for multifunctional lasers

Abstract Results on the growth technique, spectral and luminescence characteristics of Nd3+ ions in SrWO4 Raman crystals are presented. Optimal conditions to obtain optically homogeneous single crystals free of light scattering centers and growth striations were found. The values of effective segregation coefficients of active Nd and compensating Nb ions were determined. Strontium tungstate crystal exhibits one of the highest Raman gain values (5.0 cm/GW) among Nd-doped Raman host materials. Efficient intracavity Raman self-conversion in Nd3+:SrWO4 laser was demonstrated.

Growth of SBN single crystals by Stepanov technique for photorefractive applications

Abstract The Stepanov technique has been developed for SBN solid-solution crystal growth. We carried out a comparison of the growth conditions of SBN crystals in the traditional Czochralski method and new growing technique. The advantages of the Stepanov technique for growing of pure and doped SBN crystals are shown. They are high optical quality; definite form and sizes. High effective DPCM and high effective SPPCM were realized for SBN crystals doped with Ce. It was demonstrated that SBN doped with Cr and Co are promising photorefractive materials with short response time.

Insulating material: growth and characterizationGrowth of SBN single crystals by Stepanov technique for photorefractive applications

Abstract The Stepanov technique has been developed for SBN solid-solution crystal growth. We carried out a comparison of the growth conditions of SBN crystals in the traditional Czochralski method and new growing technique. The advantages of the Stepanov technique for growing of pure and doped SBN crystals are shown. They are high optical quality; definite form and sizes. High effective DPCM and high effective SPPCM were realized for SBN crystals doped with Ce. It was demonstrated that SBN doped with Cr and Co are promising photorefractive materials with short response time.

Thermal conductivity of single crystals of Ca1 − xYbxF2 + x solid solutions

The thermal conductivity of single crystals of the solid solution of yttrium fluoride in calcium fluoride Ca1 − x Y x F2 + x with the fluorite structure (x ≤ 0.20) and the Ca0.27Y0.73F2.73 phase with the tisonite structure has been studied by the absolute steady-state longitudinal heat flow method in the temperature range 50–300 K. It has been established that the thermal conductivity drops sharply with increasing yttrium trifluoride concentration, especially in the low-temperature region.

Thermal conductivity of single crystals of the Ca 1 − x Y x F 2 + x solid solution

The thermal conductivity of single crystals of the solid solution of yttrium fluoride in calcium fluoride Ca1 − x Y x F2 + x with the fluorite structure (x ≤ 0.20) and the Ca0.27Y0.73F2.73 phase with the tisonite structure has been studied by the absolute steady-state longitudinal heat flow method in the temperature range 50–300 K. It has been established that the thermal conductivity drops sharply with increasing yttrium trifluoride concentration, especially in the low-temperature region.

Growth and properties of ZnMoO4 single crystals

The crystallization conditions for obtaining zinc molybdate single crystals by the Czochralski and Kyropoulos methods from a melt have been studied. The growth parameters of large single crystals of optical quality are determined. The physicochemical and spectral-luminescent characteristics of the single crystals are studied.

Picosecond stimulated Raman scattering in crystals

The comparative values of the peak and integral cross sections of spontaneous Raman scattering and the optical dephasing time of molecular vibrations were determined for several oxide crystals by spontaneous Raman spectroscopy. The spectral, time, and energy parameters of stimulated Raman scattering (SRS) were measured for ten crystals using picosecond YLF: Nd laser pumping with a radiation wavelength of 1047 nm. An analysis of the experimental dependence of the threshold energy of pumping SRS on the integral and peak cross sections of spontaneous Raman scattering showed that the SRS gain increment explicitly depended on the integral cross section and was independent of the peak cross section of spontaneous Raman scattering as the ratio between the pumping pulse width (11 ps) and the time of optical dephasing of molecular vibrations changed from 0.42 to 9.3. The gain coefficients of steady-state stimulated Raman scattering under threshold stimulated Raman scattering conditions were determined for all the crystals studied on the basis of the measured threshold SRS pumping energies, the duration and width of the spectrum of pulses, the nonlinear interaction length, the intensity of pumping, and the theoretical dependences that relate the steady-state and transient SRS gain increments. The steady-state SRS gain coefficients obtained in this work fitted well a linear dependence on the peak cross sections of spontaneous Raman scattering, which substantiated the correctness of our analysis and measurements.

Coprecipitation from aqueous solutions to prepare binary fluorides

The synthesis of binary fluoride phases, specifically nanofluorides, by coprecipitation from aqueous solutions is considered in terms of phase equilibria. Phases have been precipitated in NaF-RF3 systems (where R stands for a rare-earth element), MF2-YF3 systems (where M = Ca, Sr, Ba), BaF2-ScF3, and CaF2-BaF2 systems. In the MF2-YF3 systems, unordered metastable congruently soluble phases are precipitated instead of ordered fluorite-like phases. In the BaF2-ScF3 system, the congruently soluble compound Ba3Sc2F12 is precipitated. In the NaF-RF3 systems, incongruently soluble metastable phases with a fluorite-like structure (for R = Er, Lu, Y) and the gagarinite structure (NaGdF4) are formed. In the CaF2-BaF2 system, intermediate phases have not been formed.

Synthesis of Ba4R3F17 (R stands for rare-earth elements) powders and transparent compacts on their base

Single-phase samples of Ba4R3F17 · nH2O (R = La, Ce, Pr, Nd, Eu, Gd, Y, Er, or Yb; n = 2.5−3.2) were prepared by coprecipitation from nitrate solutions using hydrofluoric acid. The phases crystallize in a fluorite-type face-centered cubic lattice. The dried precipitates are transparent. Scanning electron and atomic-force microscopy and X-ray diffraction line broadening show a hierarchic structure in the samples: primary nanoparticles join into agglomerates with characteristic sizes of about 150–200 nm, these agglomerates being self-packed into parallel layers with a thickness on the order of 500 nm.