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The acousto-optic figure of merit M 2 of the InI single crystal has been measured using the Dixon method at a laser-radiation wavelength of 1.15 μm. The maximum measured value was M 2 = 1100 × 10–15 s3/kg. It is comparable with the figures of merit of the most efficient acousto-optic materials: TeO2 and KRS-5. The velocities of longitudinal ultrasonic waves along the basic directions of the InI single crystal have also been measured.

In this paper a detailed study of the (ZrO2)1-x(Y2O3)x (x = 0.025 – 0.15), (ZrO2)1-x(Sc2O3)x (x = 0.06 – 0.11) and (ZrO2)1-x-y(Sc2O3)x(Y2O3)y (x = 0.07 – 0.11; y = 0.01 – 0.04) solid solution crystals grown by skull melting technique is presented. The structure, phase composition, and ion conductivity of the obtained crystals were investigated by X-ray diffraction, transmission electron microscopy, Raman scattering spectroscopy, and impedance spectroscopy. Maximum conductivity as (ZrO2)1-x(Y2O3)x and (ZrO2)1-x(Sc2O3)x solid solution crystals is observed for the compositions containing 10 mol% stabilizing oxide, and the conductivity of 10ScSZ is ~3 times higher than for 10YSZ. Experiments on crystal growth (ZrO2)1-x-y(Sc2O3)x(Y2O3)y solid solutions showed that uniform, transparent crystals 7Sc3YSZ, 7Sc4YSZ, 8Sc2YSZ, 8Sc3YSZ, 9Sc2YSZ, 9Sc3YSZ, 10Sc1YSZ and 10Sc2YSZ are single phase crystal containing t’’ phase. It is established that a necessary condition of melt growth of (ZrO2)1-x-y(Sc2O3)x(Y2O3)y single-phase crystals is the total concentration of the stabilizing oxides from 10 to 12 mol%. The addition of Y2O3 affects the (ZrO2)1-x-y(Sc2O3)x(Y2O3)y solid solution conductivity different ways and depends on the Sc2O3 content in the starting composition. The effects of structure, phase composition, concentration and type of stabilizing oxides on the electrical characteristics of obtained crystals are discussed. This article is protected by copyright. All rights reserved.

The temperature influence on diode-pumped Tm(0.4 mol%):CaF2 laser performance and tunability was investigated down to cryogenic temperatures. Laser efficiency up to 21 % and wide, red-shifted, tuning range (1783-1915 nm) was demonstrated at 80 K.

In this work the temperature dependence of spectroscopic and laser properties of new ac- tive medium Tm:SBN (Strontium-Barium Niobate, SrxBa1−xNb2O6, x = 0.61). The tested sample of Tm:SBN (2 wt. % of Tm2O3) appropriate for generation of laser radiation at 1.88 μm had plan-parallel polished faces without anti-reflection (thickness 6.65 mm). During spectroscopy and laser experiments the Tm:SBN was at- tached to temperature-controlled copper holder and was placed in a vacuum chamber. The transmission and emission spectra of Tm:SBN and the fluorescence decay time were measured depending on temperature range 80 - 350 K. The fluorescence decay time was measured to be 3.5 ms and 2.8 ms at 80 and 350 K, respectively. Longitudinal excitation of Tm:SBN was carried out by a fibre-coupled laser diode (pulse duration 10 ms, rep- etition rate 10 Hz, pump wavelength 793 nm). The laser resonator was hemispherical, 146 mm long, with flat pumping mirror (HR @1.8 - 2.1 μm) and spherical output coupler (r = 150 mm, R = 97.5 % @1.8 - 2.1 μm). The Tm:SBN laser properties were investigated at temperature range 80 - 300 K. The highest slope efficiency with respect to absorbed pumped power was 3 % at 80 K. The maximum output peak amplitude power was 0.12 W at 80 K, i.e. 3.2 times higher than it was measured at 200 K. Tunability of laser wavelength at 80 K in the range of 1827 - 1962 nm was obtained by using SiO2 birefringent filter. At 300 K, wavelength tunability reached 1859 - 1970 nm. Thus, the new Tm:SBN crystal can be an useful laser material in the region of 2 μm.

The structure and luminescent characteristics of partially yttria-stabilized zirconia (PSZ) doped with Nd 3+ ions were investigated. Transmission electron microscopy (TEM) data for PSZ crystals containing 2.8 mol.% and 3.7 mol.% Y 2 O 3 doped with Nd 2 O 3 (0.04, 0.22 and 0.34 mol.%) and containing 2.0 mol.% Y 2 O 3 doped with 0.8 mol.% Nd 2 O 3 indicated the presence of a nanosize twin domain structure. This structure becomes more homogeneous and dispersed as the total concentrations of the stabilizing oxides (Y 2 O 3 and Nd 2 O 3 ) increases. A comparison of the luminescence spectra and X-ray phase analysis results for the PSZ crystals containing 2.8 and 3.7 mol.% Y 2 O 3 with different Nd 2 O 3 concentrations (0.04, 0.22 and 0.34 mol.%) indicated that the Nd 3+ ions were predominantly concentrated in the non-transformable t′ phase. The luminescence spectra of Nd 3+ centres in these crystals were similar to those of yttrium-stabilized cubic zirconia. In the 0.8Nd 2 O 3 –2.0YSZ crystal the quantity of the non-transformable t′ phase is low, therefore the Nd 3+ ions are contained in the transformable t phase. The luminescence spectra of Nd 3+ ions occupying transformable t phase in 0.8Nd 2 O 3 –2.0YSZ crystal differs from the luminescence spectra of Nd 3+ ions in stabilized cubic zirconia.

The thermal expansion of InI crystal has been experimentally investigated in the temperature range of 51–310 K. A strong expansion anisotropy is revealed.

Already at the beginning of the laser era it was shown that Dy2+:CaF 2 lasers could be use as direct radiation sources in spectral range 2.4μm. [1] Since the Dy2+ upper laser level is strongly temperature quenched, cryogenic cooling of Dy2+:CaF 2 laser is necessary to reach efficient lasing. Thanks to long upper laser level lifetime an effective pump energy accumulation is possible and therefore the generation of 20 ns Q-switched pulses with peak power 0.5 MW was reached using Dy2+:CaF2 laser. [2] Very narrow fluorescent linewidth 0.3 cm−1 at 77 K [1] of Dy2+:CaF2 limits the shortest generated pulse length to approximately 100 ps. In the Dy2+:CaF2 crystal there are broad absorption bands in visible and near-infrared regions thus a common available laser diodes are suitable for pumping. In this work we report the first diode-pumped Dy2+ :CaF2 laser results.

Tetragonal xenotime-type yttrium orthophosphate (YPO4) Nd(3+) doped nanoparticles suitable for biomedical applications were prepared by microwave-hydrothermal treatment. We applied the energy transfer probing based on the analysis of kinetics of impurity quenching to determine the presence and spatial position of -OH fluorescence quenching acceptors in the impurity-containing nanoparticles. We show that the impurity quenching kinetics of the 0.1 at% Nd(3+) doped YPO4 nanoparticles is a two stage (ordered and disordered) static kinetics, determined by a direct energy transfer to the -OH acceptors. Analyzing the ordered stage, we assume that the origin of the -OH groups is the protonation of the phosphate groups, while analyzing the disordered stage, we assume the presence of water molecules in the mesopores. We determine the dimension of the space of the -OH acceptors as d = 3 and quantify their absolute concentration using the disordered Förster stage of kinetics. We use the late stage of kinetics of fluorescence hopping (CDD ≫ CDA) quenching (the fluctuation asymptotics) at 1 at% Nd(3+) concentration as an energy transfer probe to quantify the relative concentration of -OH molecular groups compared to an optically active rare-earth dopant in the volume of NPs, when energy migration over Nd(3+) donors to the -OH acceptors accelerates fluorescence quenching. In doing so we use just one parameter α = γ(A)/γ(D) = n(A)√[C(DA)]/n(D)√[C(DD)], defined by the relation of concentration of the -OH acceptors to the concentration of an optically active dopant. The higher is the α, the higher is the relative concentration of -OH acceptors in the volume of nanoparticles. We find α = 2.95 for the 1 at% Nd(3+):YPO4 NPs that, according to the equation for α, and the results obtained for the values of the microparameters CDD(Nd-Nd) = 24.6 nm(6) ms(-1) and CDA(Nd-OH) = 0.6 nm(6) ms(-1), suggests twenty times higher concentration for acceptors other than donors. As the main result we have established that the majority of -OH acceptors is located not on the surface of the Nd(3+):YPO4 nanoparticles, as many researchers assumed, but in their volume, and can be either associated with crystal structure defects or located in the mesopores.

Detailed studies of LaF3–NaGdF4, NaGdF4–NaLuF4, and NaLuF4–NaYF4 systems have revealed that LaF3–NaGdF4 system precipitates, formed in aqueous media, contained gagarinite-type NaGd1−xLaxF4 (x ≤ 0.0625) solid solution, tysonite-type La1−xGdxF3 (x ≤ 0.50) phase, and cubic fluorite-type NaGdF4-based phase, whereas NaGdF4–NaLuF4 precipitates contained hexagonal gagarinite-type (x ≤ 0.25) and cubic fluorite-type (x ≥ 0.675) NaGd1−xLuxF4 solid solutions. Furthermore, there were continuous series of single-phase cubic fluorite-type NaLuF4–NaYF4 solid solutions formed in the third investigated system. Crystallization of Na0.5−xLu0.5+xF2+2x solid solutions from aqueous media occurred in an incongruent manner; the use of 5-fold excess of NaF led to precipitation of NaLuF4 (x = 0) with almost stoichiometric composition.

Study of nanopowder precipitation from aqueous sodium fluoride and yttrium and/or other rare earth nitrate solutions in the presence of polyethyleneimine (PEI) has revealed the strong dependence of the solid phase composition upon the solutions’ pH values and the order of reagent addition. The conditions for single phase formation have been determined for both cubic and hexagonal NaYF 4 -type phases. Cubic single-phase samples were obtained by adding rare earth element nitrate solutions to aqueous NaF–PEI mixtures at pH = 10; while hexagonal single-phase precipitates were synthesized by the addition of aqueous NaF to aqueous rare earth element nitrate solutions + PEI mixtures at pH = 12.

A variety of Er3+-, Tm3+-, and Yb3+-activated CaF2-, SrF2-, (Ca, Sr)F2- and (Sr, Ba)F2-based fluoride laser ceramics have been prepared by the hot-forming technique. Lasing of the SrF2:Yb3+, (Ca, Sr)F2:Er3+, (Ca, Sr)F2:Tm3+, (Ba, Sr)F2:Tm3+ and (Ba, Sr)F2:Yb3+ specimens with diode pumping has been observed for the first time. Thermal conductivity data for the above fluorite-type laser materials are also presented and discussed. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

CaF2:Yb fluoride laser ceramics, prepared by hot-forming, exhibit the same optical properties as starting single crystals. Slope efficiency of the Сa0.95Yb0.05F2.05 is equal to 35% in the pulsed mode of laser operation. Decrease of ytterbium concentration in CaF2:Yb samples down to 3 mol.% resulted in the essential improvement of Сa0.97Yb0.03F2.03 thermal conductivity from 3.5 to 4.5 W/m K, but slightly decreased (down to 30%) slope efficiency of the samples under both pulsed and CW mode of operation. Alternative hot-pressing synthesis of CaF2:Yb fluoride laser ceramics provided materials with superior mechanical properties (microhardness Н = 3.2 GPa and fracture toughness К1С = 0.65 МPа m1/2) in comparison with hot-formed and/or single crystal CaF2:Yb specimens. For the first time, lasing has been observed for the novel aforementioned hot-pressed CaF2:Yb ceramics.

The structure and the spectral-luminescent properties of CaF2 — TmF3 fluoride ceramics and single crystals are studied. AFM investigations revealed a layered nanostructure of grains, which was not observed in reference samples of single crystals. It is found that the spectral-luminescent properties of CaF2 — TmF3 ceramics and single crystals are similar. Lasing at the 3F4 → 3H6 transition of Tm3+ ions in CaF2 — TmF3 ceramics (wavelength 1898 nm) under diode pimping is obtained for the first time.

Co-precipitation of barium and yttrium fluorides from aqueous solutions at room temperature produced non-equilibrium Ba1−xYxF2+x nanofluoride phase with face-centered cubic crystal lattice of fluorite-type with the composition interval of the homogeneity for x = 0.35–0.75. Lattice parameter a of this solid solution nanophase varied as a function of the sample chemical composition in a complex manner with two areas of linear dependency, from x = 0.35 to 0.45 and from x = 0.50 to 0.75. A plausible explanation of this phenomenon included a change of the type of crystal lattice defects and the manner of their population with the corresponding ions. An increase of the relative amount of yttrium in the HF reaction system led to the formation of hydroxonium salt of decafluorotriyttrium acid, (H3O+)Y3F10−·nH2O, instead of expected YF3 hydrate. No formation of oxyfluoride phases under acidic conditions has been observed.

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.

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.

Tm : CaF2 (4 mol % TmF3) single crystals and ceramic samples have been prepared, the microstructure of the ceramic has been examined by SEM and AFM, and the luminescent properties of the crystals and ceramic have been analysed.

The possibility of increasing the efficiency of one-cascade 1.5-μm SRS lasing in a BaWO4 crystal placed into an external SRS cavity and pumped by a nanosecond Nd:YAG laser at a wavelength of 1.34 μm is studied. Conditions that prevent energy outflow to the second Stokes SRS component with a wavelength of 1.78 μm are found, which allowed us to increase the efficiency of one-cascade intracavity SRS lasing at 1.53 μm up to 60% and the slope efficiency up to the quantum limit (~80% at the SRS pulse energy up to 20 mJ). The use of pumping by laser pulse trains provided the possibility of increasing the 1.53-μm SRS radiation energy to 40 mJ in a three-pulse train.

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.

Reactions of solutions of yttrium oxide in nitric acid with a 1.67 M NH4HCO3 solution were studied by direct and back titration. When the concentration of the reacting solution was within 0.031–0.052 mol/L (as Y2O3), yttrium carbonate Y2(CO3)3 · nH2O (n ≈ 2.5) of fibrous or spherulitic morphology precipitated. When the concentration was decreased to 0.022 mol/L, a new phase of platy morphology appeared. Heating these precipitates to 650–680°C yielded yttrium oxide having coherent scattering domain sizes of 40–80 nm. Y2O3 particles retain the precursor morphology.

The thermal conductivity of Ca, Sr, Ba, and Cd difluoride single crystals and the CdF2 samples doped by 3 mol % NdF3, 15 mol % HoF3, and 10 mol % ErF3 has been studied using the method of steady longitudinal heat flow in the temperature range 50–300 K. The thermal conductivity of the matrices of these compounds decreases in the order CaF2-SrF2-BaF2-CdF2. The temperature dependences of the phonon mean free path for these crystals have been calculated from experimental data and exhibit different behaviors. It has been assumed that the intense phonon scattering observed in the undoped CdF2 sample is caused by the specific features of the processes of phonon-phonon scattering. The formation of heterovalent solid solutions of cadmium difluoride and rare-earth trifluorides is accompanied by a drastic decrease in the thermal conductivity and a change in its character from that typical of dielectric single crystals to that typical of glassy materials.

In this work, a cryogenic cooled, longitudinal diode-pumped :CaF2 laser was investigated for the first time. The temperature dependence of the spectroscopy and the laser properties of :CaF2 are presented. The tested :CaF2 crystal was a longitudinal pump in a near-IR region (926 nm) by laser diode radiation. The maximal mean output power and slope efficiency at 78 K during the pulse regime of the laser were 57.5 mW and 7%, respectively. Furthermore, the CW regime was successfully tested and a maximum output power of 0.37 W was obtained for the absorbed pumping power 5.7 W. The emission laser wavelength was 2367 nm.

The optical characteristics of two Russian-made CaF2 ceramic samples are compared to those of single-crystal CaF2. The results indicate that the ceramic possesses high optical quality and a small absorption coefficient (~10-3 cm-1 at a wavelength of 1.07 μm) and is suitable as a material for optical components. Experimental evidence is presented for spatial modulation of the thermally induced depolarisation in the ceramic.

Compact schemes of a multichannel holographic laser system with short-range coupling and increased efficiency of single-mode lasing are developed for low-gain laser media operating not only at the fundamental laser transition but also at other laser transitions of the Nd:YAG crystal. The numerical simulation shows that the maximum possible number of laser channels can be increased by equalising their parameters. The possibility of phase locking of two loop Nd:YAG lasers without a nonreciprocal element with the free-running single-mode lasing efficiency up to 0.64% and the contrast of the interference pattern of the output beams exceeding 0.5 is shown experimentally.

We have studied the effect of composition and growth conditions on the structure and properties of 2.5–5 mol % Y2O3 partially stabilized ZrO2 crystals grown by directional solidification in a cold-wall crucible. The phase composition and density of the crystals have been determined. The crystals are shown to be uniform in composition, with local changes in Y2O3 content within ±0.5 mol %. The dimensions and quality of the single crystals are influenced by the growth conditions.

The effect of hydrothermal and ultrasonic/hydrothermal treatment on the phase composition and micromorphology of yttrium hydroxocarbonates has been studied. The hydrothermal treatment of a sus- pension of amorphous yttrium hydroxocarbonate hydrate, Y ( OH ) CO 3 · 1.25 H 2 O, does not significantly alter the composition of the powder, while ultrasonication directly in the course of hydrothermal treatment under the same conditions yields crystalline yttrium hydroxocarbonate Y ( OH ) CO 3 . The thermolysis of yttrium hydroxo- carbonates Y ( OH ) CO 3 · x H 2 O and Y ( OH ) CO 3 has been studied.

Mid-IR Nd 3+ transitions perspective for laser oscillation were analyzed in the CaGa2S4, PbGa2S4, and PbCl2 crystals and compared with low phonon fluoride crystals. Fluorescence kinetics decay of the high-lying 4 G7/2 and 4 G5/2; 2 G7/2 and low-lying 4 IJ levels and its temperature dependence in the range of 13–295 K were measured. For 5 lm mid-IR transitions of Nd 3+ the radiative relaxation rates are found to be several times higher and multiphonon relaxation (MR) rates are several times lower in lead and calcium thiogallate crystals compared to low phonon fluoride crystals. MR rate dependence on the Nd 3+ to the nearest ligand distance R0 is established experimentally and analyzed in the frame of point-charge model of nonlinear theory of multiphonon relaxation. Mid-IR Nd 3+ 4–5.5 lm fluorescence spectra of 4 Ii– 4 Ij transitions perspective for laser oscillation were measured for the first time in the studied crystals.

A method of phase locking of a parallel multichannel laser system by holographic gain gratings in the active laser medium at a long-range holographic coupling of laser channels is developed. The oscillation dynamics of a three-channel holographic Nd:YAG laser system is simulated by considering the phase-locking conditions depending on the relative gain mismatch in laser channels. The conditions of lasing with the gain-selected control laser channel are found under which controlled channels are phase-locked even in the case of the threefold difference in their gains.

The conditions of phase locking of a three-channel holographic Nd:YAG laser system based on self-pumped phase-conjugate oscillators emitting giant 100-mJ, 60-ns monopulses in each of the channels are investigated experimentally. The pulse-to-pulse stable self-phase-locking of the laser system with a pulse repetition rate up to 20 Hz is obtained. The mutual coherence of laser channels was increased up to 0.87 by separating the controlling channel which initiates lasing in a set of controllable channels generating synchronous monopulses.

The possibilities of enhancing the efficiency of laser drilling of micron holes, increasing their depth, and eliminating their conic shape are studied by using a single-mode loop Nd:YAG laser with self-phase conjugation on the gain gratings and passive Q-switching by a scanned gradiently coloured F2-:LiF crystal. Holes of diameters 15–150 μm and depth up to 20 mm with the aspect ratio (ratio of the hole depth to its diameter) of 50–155 are drilled in various metals and alloys. It is shown that passive Q-switch scanning during drilling provides the increase in the depth and speed of the laser drilling of superdeep holes by a factor of 1.5–2.

The goal of this work was an investigation of the temperature influence (in range from 80 up to 330 K) on the laser properties of Er:CaF 2 ceramics, which is suitable as a gain medium for generation of radiation at 2.7 μm. The tested Er:CaF 2 ceramics sample, prepared using a hot-forming technique, was doped with 5.5% of ErF 3 . The sample was in the form of plane-parallel face-polished 5.8mm thick plate (without AR-coatings). It was mounted in a temperature controlled cupreous holder, placed inside the vacuum chamber of the liquid nitrogen cryostat. A fiber coupled laser diode, operating in pulsed regime (3 ms pulse length, 20 Hz repetition rate) at wavelength 968 nm, was used for Er:CaF 2 sample pumping. The 145mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 2.65 − 2.95 μm, HT @ 0.97 μm) and a curved (r = 150mm) output coupler with a reflectivity of ∼ 97% @ 2.65 − 2.85 μm. From the results it follows that the temperature of the active medium has a strong influence mainly on laser threshold (more than 8 times lower threshold power corresponded to the temperature 80K in respect to 330 K). The highest slope efficiency (2.3% in respect to absorbed power), obtained for the temperature 80 K, was more than twice higher than the slope efficiency for 330 K.

The Tm(0.4 wt.%):CaF2 crystal and ceramics were investigated. Possible forming of new Tm3+optical centers during the hot-forming procedure was observed. Broad laser tunability in range 1820-1910 nm was obtained.

Investigations of the spectroscopic and laser properties of Fe2+ ions in Zn1-xMgxSe and Zn1-xMnxSe solid solutions with different content x are carried out in the 77-300 K temperature range. The influence of the matrix material on the Fe2+ ion properties is discussed.

Spectral characteristics of Fe:CdMnTe active material with different Cd-Mn composition are presented as well as the temperature dependence of fluorescence spectra and decay time.

The dynamics of Tm3+ optical centers formation with increasing 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.

We studied how hydrothermal treatment per se or combined ultrasonic-hydrothermal treatment affects the micromorphology and phase composition of yttrium hydroxonitrates. We show that ultrasonication during the hydrothermal treatment of yttrium hydroxonitrate suspensions of the bulk composition Y(OH)2.53(NO3)0.47 · 0.16H2O produces yttrium oxohydroxonitrate crystals of the composition YO0.25(OH)2.25(NO3)0.25.

The spectral and lasing parameters of Yb3+ ions in zirconium dioxide crystals with a stabilised cubic structure (fianites) are studied. It is found that the absorption and luminescence spectra of Yb3+ in these crystals are characterised by a considerable inhomogeneous broadening. The nature of this broadening is investigated and the model of optical centres consistent with the properties of the inhomogeneous spectra of Yb3+ in the cubic zirconium dioxide crystal is proposed. It is shown that fianites can be used in solid-state lasers. Lasing in Yb3+ ions in diode-pumped fianite crystals was obtained and studied.

The spectral and kinetic properties of yttrium—aluminium garnet crystals co-doped with Er3+ and Yb3+ are studied in the range from room temperature to 800 °C. It is found that the lifetime of the 4I11/2 level of the erbium ion decreases approximately by a factor of twenty with increasing temperature and the efficiency of nonradiative energy transfer from Yb3+ to Er3+ increases considerably. Analytic expressions describing the spectral and temperature dependences of the absorption and emission cross sections for the transition between the 4I13/2 and 4I15/2 levels of the erbium ion are proposed.

CW lasing is obtained in Er3+(5%) : CaF2 and Er3+(5%) : SrF2 crystals near 2.75 μm with 0.4 and 2 W of output powers, respectively, upon transverse diode laser pumping into the upper 4I11/2 laser level of erbium ions at 980 nm. Continuous tuning of the laser wavelength between 2720 and 2760 nm is realised in the Er3+ : SrF2 crystal.

Ceramic and crystalline weakly guiding optical fibres with the core – cladding refractive index difference of 10-2 – 10-4 are fabricated by a hot pressing method. The waveguides with one or several cores for operation in the spectral range 0.2 – 5 μm are produced. The waveguides are based on CaF2, SrF2, and BaF2 ceramics and crystals and their solid solutions doped with trivalent Pr, Nd, Tb, Dy, Yb, Ho, Er, and Tm ions, as well as on LiF ceramics and crystals with colour centres. The first results of investigation of the lasing properties of ceramic SrF2 : NdF waveguides under diode pumping are presented, and the prospects of further investigation are discussed.

The spectral and lasing properties of Cr2+:ZnS and Cr2+: ZnSe crystals pumped by Raman-shifted nanosecond neodymium lasers are studied. Tunable pulsed lasing is obtained in the mid-IR range between 2.05 and 2.40 μm. The minimum lasing threshold was 170 μJ at the maximum slope efficiency of 20 %.

A method of phase locking of optically coupled lasers by gain gratings in an active medium is proposed. The criterion for phase locking is determined and optimal relations between the energy parameters of waves upon four-wave mixing are found. Two-channel parallel laser systems based on self-phase-conjugation loop oscillators are studied and the possibility of their phase locking with the phasing degree up to 0.9 is shown.

An express technique is proposed for the study of stimulated Raman scattering (SRS) in crystals excited by long trains of picosecond pulses. SRS was studied in several crystals excited by 15-ps pulses from an Nd3+:CLNGG disordered garnet laser. SRS in SrMoO4 and Ca3(VO4)2 crystals was obtained and investigated for the first time, and compared with SRS in popular SRS-active BaWO4 and KGd(WO4)2 crystals.

The site-selective and time-resolved fluorescence laser spectroscopy and kinetic measurements with high spectral and nanosecond temporal resolution was applied to analyze the high-energy wing of the M and N absorption bands of the 4I9/2(1)→4G5/2(1) crystal-field (CF) transition in a CaF2:Nd3+ (0.6 wt%) crystal at 4.2 K. It was found that at helium temperatures the dynamically split spectral line assigned as the 4I9/2(1)→4G5/2(1) (CF) transition of coherently coupled Nd3+ ions in the pair M- and quartet N-centers of CaF2:Nd3+ (0.6 wt%) is inhomogeneously broadened. It consists of the pair M- and quartet N-centers with at least 0.1 A variation of the positions of the fluorescence-excitation spectral lines registered at the 4F3/2(1)→4I9/2(1) CF transition. Small fluorescence-lifetimes variation of the 4F3/2 and 4D3/2 levels from the small variation of the distances R between Nd3+ ions in the pair is found. At least 2.7% variation of the value of the Nd–Nd distance R in the pair M-center was determined from the lifetime variation of the 4F3/2 manifold with the assumption of a dipole–dipole interaction between the ions in the pair. The energy transfer up-conversion process responsible for the UV fluorescence observed when pumping the 4I9/2(1)→4G5/2(1) transition has been determined.

A new strong erbium laser glass (SELG) based on a boro-alumo-phosphate composition is reported. We discuss the synthesis and chemical properties together with spectroscopic and thermo-mechanical da ...

Cubic single-phase samples of the title nanopowders are obtained by addition of rare earth nitrate solutions to aqueous NaF/polyethyleneimine mixtures at pH 10, whereas single-phase hexagonal precipitates are prepared by addition of aqueous NaF solutions to aqueous rare earth nitrate/polyethyleneimine mixtures at pH 12.

The Tm:CaF2 (4% of TmF3) and Tm:Ho:CaF2 (2% of TmF3, 0.3% of HoF3) ceramics, prepared using hot pressing, and hot formation technique had been used as an active medium of diode pumped mid-infrared tunable laser. A fibre (core diameter 400 μm, NA = 0.22) coupled laser diode (LIMO, HLU30F400-790) was used to longitudinal pumping. The laser diode was operating in the pulsed regime (6 ms pulse length, 10 Hz repetition rate). The duty-cycle 6% ensures a low thermal load even under the maximum diode pumping power amplitude 25W (ceramics samples were only air-cooled). The laser diode emission wavelength was 786 nm. The 80mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 1.85 − 2.15 μm, HT @ 0.78 μm) and a curved (r = 150mm) output coupler with a reflectivity of ∼ 98% @ 1.85 − 2.0 μm for Tm:CaF2 laser or ∼ 99.5% @ 2.0 − 2.15 μm for Ho:Tm:CaF2. Tuning of the laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle. Both samples offered broad and smooth tuning possibilities in mid-IR spectral range and the lasers were continuously tunable over ∼ 100 nm. The obtained Tm:CaF2 tunability ranged from 1892 to 1992nm (the maximum output energy 1.8mJ was reached at 1952nm for absorbed pumping energy 78 mJ). In case of Tm:Ho:CaF2 laser tunability from 2016 to 2111nm was reached (the maximum output energy 1.5mJ was reached at 2083nm for absorbed pumping energy 53 mJ). Both these material are good candidates for a future investigation of high energy, ultra-short, laser pulse generation.