V. A. Konyushkin

Efficient laser based on CaF 2 -SrF 2 -YbF 3 nanoceramics

CaF(2)-SrF(2)-YbF(3) fluoride ceramics of high optical quality was prepared, and its absorption, fluorescence, and laser oscillation properties were investigated. Oscillation slope efficiency that was only a few percent lower than that for a single crystal of similar composition was demonstrated under diode pumping.

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.

SrF2:Nd3+ laser fluoride ceramics

SrF(2):Nd(3+) fluoride ceramics of high optical quality was prepared and its spectroscopic and laser properties investigated. Oscillations of different optical centers depending on the excitation wavelength were obtained with a slope efficiency of up to 19%.

Beam-quality improvement of a passively Q-switched Nd:YAG laser with a core-doped rod

We present experimental results that demonstrate the great efficiency of a core-doped Nd:YAG rod (a hexagonal Nd:YAG core surrounded by undoped YAG) in producing high output power and excellent beam quality. An additional improvement in beam quality is clearly observed when the core-doped rod is used in combination with a LiF:F(2)(-) crystal, which acts as a passive Q-switching element. This improvement is quantified by beam-propagation factors as low as M(2) approximately = at a maximum average output power of 9 W. We show that transversally pumped core-doped rods with the addition of LiF:F(2)(-) crystals fulfill the requirements for high-beam-quality, scalable, compact all-solid-state lasers in passively Q-switched operation.

Evolution of yttria nanoparticle ensembles

The formation of Y2O3 nanoparticles in precipitation from acidic nitrate aqueous solutions, which was done by regulating pH at the expense of their titration with an ammonium hydroxide aqueous solution, was studied. The jellylike precipitates of a (Y2(OH)5NO3 · nH2O, n = 2, 3) precursor lose their volatile components under heating and drying in several stages. Their chemical decomposition terminates at 500–550°C with the formation of the cubic modification of yttria. Yttria particles inherit the platelike morphology of the particles of their precursor. Under further heating, Y2O3 particles lose their nonequilibrium shape due to the decomposition of plates into roundish nanoparticles with the relief of mechanical stresses. The isothermal exposure of nanoparticles formed in this way leads to their stepped agglomeration with a sequential increase in the size of particles by an order of magnitude. The sintering of Y2O3 powders with the formation of ceramics was investigated.

Spectroscopic and laser properties of Tm3+ optical centers in CaF2 crystal under 795 nm diode laser excitation

The dynamics of Tm3+ optical center formation with increasing thulium concentration and the influence of different optical centers on the fluorescence and laser properties of the 2 μm 3F4–3H6 transition under ~795 nm laser diode excitation is studied.

Thermophysical characteristics of Ca1−xSrxF2 solid-solution Crystals (0 ≤ x ≤ 1)

The thermal conductivity of crystals of a continuous series of isovalent Ca1 − xSrxF2 solid solutions has been experimentally investigated in the temperature ranges of 50–300 K (0 ≤ x ≤ 1) and 54–303 K (x = 0.743). The concentration dependence k(x) of the thermal conductivity has been revealed for Ca1−xSrxF2 crystals. It is shown that k > 3 W/(m K) at 300 K for any x. Being extrapolated to the melting temperature range, the phonon mean free path l(T) in Ca0.257Sr0.743F2 crystal approaches to the unit-cell parameter a.

Heat conductivity of Ca1-xRxF2+x (R = La, Ce, or Pr; 0 ≤ x ≤ 0.25) heterovalent solid solutions

Heat conductivity of crystals of Ca1–xRxF2 + x (R = La, Ce, or Pr; 0 ≤ x ≤ 0.25) solid solutions with a fluorite structure has been experimentally investigated in the temperature range of 50–300 K. The introduction of heterovalent impurities into CaF2 significantly reduces heat conductivity, especially at low temperatures. The concentration dependences of the heat conductivity of the solid solutions studied are close because they contain defect clusters of the same type.

Thermal conductivity of LaF3-based single crystals and ceramics

The thermal conductivity of lanthanum fluoride based single crystals and ceramics (LaF3, La0.975Nd0.025F3, and La0.95Sr0.05F2.95) has been measured at temperatures from 50 to 693 K by an absolute steady-state axial flow technique. We have not detected any anomalies indicative of “two-level systems.” The heat capacity of LaF3 single crystals has been measured in the temperature range 56–300 K. The results are used to evaluate the c-axis phonon mean free path as a function of temperature for single-crystal LaF3.