Effect of the synthesis technique on the physicochemical properties of Ce<Subscript>0.8</Subscript>(Sm<Subscript>0.75</Subscript>Sr<Subscript>0.2</Subscript>Ba<Subscript>0.05</Subscript>)<Subscript>0.2</Subscript>O<Subscript>2 − δ</Subscript>

A multicomponent solid electrolyte of composition Ce_0.8(Sm_0.75Sr_0.2Ba_0.05)_0.2O_{2 − δ} has been synthesized by three different techniques: solid-state reaction, laser evaporation, and the glycine nitrate process. Its microstructure, sintering kinetics, and electrical properties have been studied in relation to the synthesis technique. Ceramics produced using laser evaporation consisted of submicron (0.2 μm) grains and offered the highest electrical conductivity: 27 × 10⁻³ S/cm at 873 K.     

Laser implantation of impurities in cadmium telluride crystals

Processes of laser implantation of shallow donors (aluminum and indium) and an acceptor (antimony) in CdTe crystals (n,p∼10¹⁵ cm⁻³) are investigated. Thin dopant films vacuum deposited on the etched surface of the crystals are irradiated by ruby (λ=0.694 μm) and Nd:YAG (λ=1.06 μm) laser pulses (pulse duration 20 ns) over a wide energy interval (0.1–1.8 J/cm²). The irradiated surfaces are studied by x-ray microanalysis, Auger spectroscopy, and the thermopower method. It is it is shown that irradiation by a Nd:YAG laser produces a uniform doping of a subsurface layer of the crystal by aluminum. The implantation of indium leads to the formation of a precipitate. The concentration of implanted impurities reaches 10¹⁹–10²¹ cm⁻³. Pis’ma Zh. Tekh. Fiz. 24, 1–6 (June 12, 1998)     

Composite phosphor films based on spherical Lu2O3:Eu3+ nanoparticles

A nanopowder of Lu₂O₃:Eu³⁺ (C _Eu = 5 at.%) was obtained by coprecipitation with urea (NH₂)₂CO from aqueous solutions. Using this nanopowder, compact Lu₂O₃:Eu³⁺ films with thicknesses within 20–200 μm and a relative density up to 65% of the theoretical limit were deposited using the spin-coating and painting techniques. The films were characterized by scanning electron microscopy, X-ray diffraction, and X-ray luminescence (XRL) measurements. It is established that the XRL intensity depends on the phosphor/organic binder ratio and thickness of the film. The most intense XRL and most homogeneous structure are observed for 20-μm-thick Lu₂O₃:Eu³⁺ films.     

Laser-diode pumped passively Q-switched Nd3+:NaY(WO4)2 laser with Cr4+:YAG saturable absorber

A laser-diode pumped passively Q-switched new type crystal Nd³⁺:NaY(WO₄)₂ (known as Nd:NYW) laser with Cr⁴⁺:YAG saturable absorber has been realized. The dependence of pulse repetition rate, pulse energy, pulse width, and peak power on pump power for different small-signal transmission of Cr⁴⁺:YAG are measured. The coupled rate equations are used to simulate the Q-switched process of laser, and the numerical solutions agree with the experimental results.     

Pump beam waist-dependent pulse energy generation in Nd:YAG/Cr4+:YAG passively Q-switched microchip laser

Abstract

The incident pump beam waist-dependent pulse energy generation in Nd:YAG/Cr⁴⁺:YAG composite crystal passively Q-switched microchip laser has been investigated experimentally and theoretically by moving the Nd:YAG/Cr⁴⁺:YAG composite crystal along the pump beam direction. Highest pulse energy of 0.4 mJ has been generated when the Nd:YAG/Cr⁴⁺:YAG composite crystal is moved about 6 mm away from the focused pump beam waist. Laser pulses with pulse width of 1.7 ns and peak power of over 235 kW have been achieved. The theoretically calculated effective laser beam area at different positions of Nd:YAG/Cr⁴⁺:YAG composite crystal along the pump beam direction is in good agreement with the experimental results. The highest peak power can be generated by adjusting the pump beam waist incident on the Nd:YAG/Cr⁴⁺:YAG composite crystal to optimize the effective laser beam area in passively Q-switched microchip laser.     

Use of Nd: YAG laser forin situ growth of thin films of Y1Ba2Cu3O7−δ

As-deposited superconducting films of Y₁Ba₂Cu₃O_7−δ with zero resistance at a temperature of ⋍ 80 K have been successfully grown using a Nd:YAG laser. A substrate temperature in the range 450–550°C was found most appropriate. The use of a Nd:YAG laser instead of an excimer laser is likely to improve the cost effectiveness of the laser ablation technique.     

Enhancement of stability and peak power in a diode-pumped doubly QML YVO4/Nd:YVO4 laser with EO and Cr:YAG saturable absorber

A diode-pumped doubly Q-switched and mode-locked (QML) YVO₄/NdYVO₄ laser is realized with the electro-optic (EO) modulator and Cr⁴⁺:YAG saturable absorber, in which the repetition rate of the Q-switched envelope is controlled by the active EO modulation while the mode-locked pulses inside the Q-switched envelope depend on both the actively modulated loss and the passive saturable absorption. The experimental results show that the doubly QML laser can generate more stable and shorter pulses with higher peak power when compared with the singly passively QML laser with Cr⁴⁺:YAG. At the pump power of 20 W and the repetition rate 1 kHz, a 21 ns Q-switched pulse envelope with a average mode-locked peak power of 544 kW is obtained, which is the shortest Q-switched pulse envelope to my knowledge. In comparison to the singly passively QML laser with Cr⁴⁺:YAG, the doubly QML laser has compressed the Q-switched envelope pulse width 70% and improved the mode-locked pulsed peak power 27 times. By using a hyperbolic secant square function and considering the Gaussian distribution of the intracavity photon density, the coupled equations for diode-pumped dual-loss-modulated QML laser is given and the numerical solutions of the equations are in good agreement with the experimental results.     

GeSe2–Ga2S3–PbI2 as materials for IR-stimulated optical second harmonic generation

We have observed a several times enhancement of the IR optical second harmonic generation of GeSe₂–Ga₂S₃–PbI₂ glasses for the fundamental wavelength 10.6 μm. The investigations were performed after the previously treatment of the glasses by the two coherent laser beams generating by the same laser––the first one at 10.6 μm and another ones at doubled frequency (5.3 μm) obtained like a second harmonic generation signal. We have found that the maximal optical second harmonic generation was achieved during illumination by the fundamental CO₂ laser beam with power density about 1.8 GW/cm² _, temperature about 425 °C corresponding to the glassing transitions and ratio power intensity ratio between the fundamental and doubled frequency beams about 25.     

Refractive index patterning of tellurite glass surfaces by ultra short pulse laser spot heating

Dot patterns of refractive indices were formed by the laser pulse irradiation on the tellurite glasses. The ternary tellurite glasses of TeO₂-Na₂O-Al₂O₃, TeO₂-Na₂O-GeO₂ and TeO₂-Na₂O-TiO₂ doped with 2 mol% of CoO were irradiated by a femtosecond pulse laser beam (800 nm) or by a green light beam (532 nm) from a second harmonic generator of a Q switch pulse YAG laser. The refractive index map of the glass was composed with an He-Ne laser beam by an scanning ellipsometric technique at a resolution of 100 m × 50 m, indicating that the spots possessing refractive index lower by about 0.05–0.38 than the surroundings were formed at the region irradiated by the laser beam. The irradiation of the femtosecond laser beam generated the dot patterns roughly equivalent to the beam size. The change of refractive index could be tunable by adjusting laser power, suggesting that the process could be applied to optical recording.     

HTSC Josephson junctions anddc SQUIDs onSrTiO 3 bicrystal substrates grown by floating zone method

A new approach to the fabrication of a SrTiO₃ bicrystal substrate based on the technology of growing by floating zone method natural SrTiO₃ bicrystals with misorientation angles 24° and 37° has been developed. Thin film YBCO Josephson junctions and dc SQUIDs on SrTiO₃ bicrystal substrates were fabricated and studdied at T=77 K. A critical current density j_c and I_cR_n product for the junctions with misorientation angle α=24° were close to 2×10⁴ A/cm² and 190÷260 μV respectively, while for α=37° it were found that j_c≈2×10³ A/cm² and I_cR_n≈90÷120 μV. The dc SQUIDs were made with typical inductances 20÷80 pH, critical currents of 20÷150 μA and resulting voltage modulation 10÷40 μV. Noise measurements performed at 77 K revealed low 1/f noise with cut-off frequency about 10 Hz.     

Studying diffusion in multilayer thin-film structures on silicon by the contact melting technique

Features of the contact melting in thin-film structures comprising an aluminum layer with a thickness of h ₁ = 5 μm and a metal (Ti, Ni, Mo) or semiconductor (Si, Ge) sublayer (h ₂ = 0.1 μm) on a single crystal silicon plate (h ₃ = 500 μm) have been studied. The contact melting was caused by single rectangular electric pulses with a current density of j < 9 × 10¹⁰ A/m² and a duration of τ = 100–1000 μs passing through the Al layer. The duration and rate of melting in the samples were determined using voltage waveforms measured by an oscillograph. A method has been developed based on an analysis of the mechanisms of contact interaction in the Al film—sublayer system (with allowance for experimental data on the time of sublayer dissolution in the Al film) for estimating the coefficients of mutiphase diffusion of the system components during the passage of a current pulse.     

Magnetic properties of oxide nanopowders obtained by pulsed electron beam evaporation

The magnetic properties of oxide nanopowders obtained by pulsed electron beam evaporation of targets in a low-pressure gas phase have been studied. Using this method, we obtained Zn-ZnO and ZnO nanopowders with the specific magnetization amounting to 2.8 × 10⁻² and 2 G cm³/g, respectively. Significant room-temperature ferromagnetism has been observed for the fist time in a nanopowder of yttria-stabilized zirconia, where the specific magnetization reached ∼6.7 × 10⁻² G cm³/g.     

Laser induced structure transformation in Co70Fe3Mn3.5Mo1.5B11Si11 amorphous alloy

Laser induced structure changes in amorphous Co₇₀Fe₃Mn_3.5Mo_1.5B₁₁Si₁₁ alloy have been studied by means of X-ray diffraction and magnetic properties measurements. Both three types of structural relaxations and a starting stage of crystallization process are considered as main characteristics of structure transformation upon laser treatment. Results of investigation of this amorphous alloy at different parameters of laser irradiation have shown that this alloy becomes partly crystalline after irradiation with laser pulse fluence of about 1.8 J/mm² and pulse duration τ = 2 × 10^?5 sec. Increasing of laser pulse fluence above 2.0 J/mm² leads to the destruction of ribbon, due to intensive evaporation.     

LEDs based on InAsSbP/InAsSb heterostructures (λ = 4.7 μm) for carbon monoxide detection

Light-emitting diodes (LEDs) operating in the 4.4–4.8-μm wavelength range have been developed for detecting the presence of carbon monoxide (CO) in air. The proposed LEDs are based on InAsSbP/InAsSb heterostructures with InAs_0.85Sb_0.15 active region, which were grown by metalorganic vapor-phase epitaxy. The electrolumuinescent properties of LEDs have been studied. The output power of LED operating in a pulsed mode reaches 50 μW at a current pulse amplitude of 2 A, and that in a quasi-continuous wave mode is 1 μW at a current of 200 mA. The absorption of LED radiation in a gaseous medium containing 10% CO has been studied. The proposed LEDs can be used to simultaneously detect both CO₂ (absorbing at λ = 4.3 μm) and CO (λ = 4.67 μm).     

Direct fabrication of surface relief gratings in chalcogenide glasses by excimer laser interference lithography

In this paper we study the possibility to realise surface relief gratings in thin chalcogenide glass films by holographic exposure using a pulsed KrF excimer laser. Gratings with a period of 540 nm and depths of 100–300 nm were patterned at the surface of 1 μm thick films. Due to coupling of an incident near-infrared laser beam to waveguide modes a resonance-like polarisation dependent decline of transmission was observed at specific incidence angles. Just one laser pulse with a fluence of 12 mJ/cm² per beam was sufficient to achieve the required grating parameters in sulphide glasses with low T _g.     

Low-loss,high-purity (TeO<Subscript>2</Subscript>)<Subscript>0.75</Subscript>(WO<Subscript>3</Subscript>)<Subscript>0.25</Subscript> glass

By melting a mixture of high-purity oxides in a platinum crucible under flowing purified oxygen, we have prepared (TeO₂)_0.75(WO₃)_0.25 glass with a total content of 3d transition metals (Fe, Ni, Co, Cu, Mn, Cr, and V) within 0.4 ppm by weight, a concentration of scattering centers larger than 300 nm in size below 10² cm⁻³, and an absorption coefficient for OH groups (λ ∼ 3 μm) of 0.008 cm⁻¹. The absorption loss in the glass has been determined to be 115 dB/km at λ = 1.06 μm, 86 dB/km at λ = 1.56 μm, and 100 dB/km at λ = 1.97 μm. From reported specific absorptions of impurities in fluorozirconate glasses and the impurity composition of the glass studied here, the absorption loss at λ ∼ 2 μm has been estimated at ≤100 dB/km. The glass has been drawn into a glass-polymer fiber, and the optical loss spectrum of the fiber has been measured.     

Electrokinetic properties of Nd:YAG nanopowder and a high concentration slurry with ammonium poly(acrylic acid) as dispersant

The electrokinetic properties of Nd:YAG nanopowder with particles of about 40 nm in diameter were investigated by measuring the zeta potential of a stable YAG (Y₃Al₅O₁₂) aqueous slurry. Ammonium poly(acrylic acid) polyelectrolyte was used as dispersant to adjust the electrokinetic properties of the Nd:YAG slurry. The effect of the pH of the slurry and of the polyelectrolyte concentration on the stability of the suspension are discussed in this study. The optimal pH value and the amount of dispersant needed to obtain a stable Nd:YAG nanoparticle slurry were determined. Highly consistent Nd:YAG nanoparticle slurries with optimal pH and dispersant concentration were prepared by ball milling. The rheological behavior of Nd:YAG slip with different solid loading (60–70 wt%) has been studied by measuring the viscosity and shear stress as a function of shear rate. Slip with solid loadings of 65 wt% shows near-Newtonian behavior but becomes non-Newtonian with typical shear-thinning behavior above this solid loading value. The density and microstructure of the cast product bears a direct relationship to the state of the slip induced by alternation of the pH and the concentration of the dispersant as well as the solid loading.     

Three-primary-color upconversion luminescence in rare earth-doped <Emphasis Type="Italic">β</Emphasis>-NaLuF<Subscript>4</Subscript> microtubes

Lanthanide ions-doped NaLuF₄ hexagonal-prismatic microtubes have been successfully synthesized via a facile hydrothermal approach for the first time. The as-grown microtubes are determined to be pure hexagonal (β-) NaLuF₄ phase with an outermost diameter of about 3 μm and a length of approximately 40 μm. The Yb³⁺/Er³⁺(Tm³⁺)-codoped NaLuF₄ microtubes emit bright three-primary-color (red, green, and blue) light under 980 nm laser diode excitation undergoing an upconversion. Mechanisms for the excitation and emission were analyzed based on the emission spectra, the plot of luminescence intensity to pump power and a simplified energy level diagram.     

Cw and passively Q-switched laser performance of a mixed c-cut Nd:Gd0.33Lu0.33Y0.33VO4 crystal operating at 1.34 μm

Continuous wave and passively Q-switched laser operation with a mixed c-cut Nd:Gd_0.33Lu_0.33Y_0.33VO₄ crystal at 1.34 μm has been realized for the first time as far as we know. The largest output power of the continuous wave was 1.1 W for the output mirror of 5% transmission, with the optical conversion efficiency and the slope efficiency being 15% and 17.2%, respectively. The passive loss and the stimulated emission cross-section of the Nd:Gd_0.33Lu_0.33Y_0.33VO₄ crystal were found to be 0.6% and 0.47 × 10⁻¹⁹ cm². The thermal lens effect that weakened the laser performance has also been measured. For passively Q-switched operation, the shortest pulse duration of 26 ns, the highest peak power of 1.8 kW, along with the pulse energy as large as 47 μJ, were obtained using V:YAG as Q-switch. The experimental results have shown that the passively Q-switched Nd:Gd_0.33Lu_0.33Y_0.33VO₄ laser can generate pulses with larger pulse energy and higher peak power in comparison with the passively Q-switched Nd:GdYVO₄ lasers.     

Laser surface modification for synthesis of textured bioactive and biocompatible Ca–P coatings on Ti–6Al–4V

A textured calcium phosphate based bio-ceramic coating was synthesized by continuous wave Nd:YAG laser induced direct melting of hydroxyapatite precursor on Ti–6Al–4V substrate. Two different micro-textured patterns (100 μm and 200 μm line spacing) of Ca–P based phases were fabricated by this technique to understand the alignment and focal adhesion of the bone forming cells on these surfaces. X-ray diffraction studies of the coated samples indicated the presence of CaTiO₃, α-Ca₃(PO₄)₂, Ca(OH)₂, TiO₂ (anatase) and TiO₂ (rutile) phases as a result of the intermixing between the precursor and substrate material during laser processing. A two dimensional elemental mapping of the cross-section of the coated samples exhibited the presence of higher phosphorous concentration within the coating and a thin layer of calcium concentration only at the top of the coating. Improved in vitro bioactivity and in vitro biocompatibility was observed for the laser processed samples as compared to the control.