自变频激光晶体Nd3+:GdAl3(BO3)4的研究

采用熔盐法生长出尺寸为30mm的Nd3+:GdAl3(BO3)4优质晶体,进行了吸收光谱和荧光光谱的测定研究,计算得到晶体发射截面为σ1061.9e=2.9×10-19cm2和σ1338nme=5.5×10-20cm2.采用染料激光器作为泵浦源,对晶体进行了自变频激光实验研究,在紫外可调谐(378～382nm)、绿光531nm、蓝光(436～443nm)、红光(669nm)和红外可调谐(1305～1365nm)波段实现了激光输出,输出的最大功率分别为:105μJ/脉冲、119.5μJ/脉冲、445μJ/脉冲、19μJ/脉冲和31μJ/脉冲.     

Luminescent properties of YAl3(BO3)4:Eu3+ phosphors

YAL₃(BO₃)₄:Eu³⁺ phosphors were fabricated by the sol-gel method. The structure properties were measured by x-ray diffraction (XRD) and infrared spectra (IR). Doping concentration of Eu³⁺ ions in YAL₃(BO₃)₄:Eu³⁺ phosphors of 0, 1, 3, 4, and 5 mol% were studied. The excitation spectra and emission spectra of YAL₃(BO₃)₄:Eu³⁺ phosphors were examined by fluorescent divide spectroscopy (FDS). The luminescent properties of YAL₃(BO₃)₄:Eu³⁺ phosphors are discussion. The optimal doping concentration of Eu³⁺ ions in YAL₃(BO₃)₄:Eu³⁺ phosphors was found to be approximately 3 mol%.     

The sol-gel process synthesis of GdAl3(BO3)4:Eu3+ nanophosphors

GdAl3(BO3)4:Eu3+ red phosphors were prepared using citric acid as complex agent by sol-gel technique. The preparation conditions of the precursor synthesis, including crystallization temperature and crystallization time were investigated. Their structure and luminescence properties were characterized by X-ray diffraction (XRD) analysis and fluorescence spectrometry. The results showed that GdAl3(BO3)4:Eu3+ phosphor crystallized at 960 degrees C for 2 h have been synthesized by sol-gel method. The phosphor is distributed into hexagonal system and the lattice parameters are a = 9.2992 nm c = 7.2577 nm. The excitation spectrum of Gd(0.95)Al3(BO3)4:Eu(0.05)3+ samples is complex and the frequency scale is wide. It consists of a number of main excitation transitions namely 8S(7/2) --> 6IJ (270 nm) of Gd3+, and the others 7F0 --> 5L6 (400 nm), 7F0 --> 5D2 (472 nm) and 7F0 --> 5D1 (542 nm) of Eu3+. The main emission peaks are 614 nm and 619 nm, which are the characteristic emission peaks of Eu3+. These emission peaks correspond to the transition from 5D0 to 7F2 of Eu3+. The shape and the wavelength range of the emission spectrum are similar when the sample was excited by different excitation spectrum. Only the relative intensity of the emission peaks is different from each other.     

Tri-wavelength passively Q-switched Yb3+:GdAl3(BO3)4 solid-state laser based on WS2 saturable absorber

Using the WS₂ nanosheets prepared by a facile hydrothermal reaction as saturable absorber (SA), we demonstrate a tri-wavelength passively Q-switching operation of a diode-pumped Yb:GdAl₃(BO₃)₄ (Yb:GAB) crystal laser for the first time. The single pulse energy up to 1.30 μJ with the output power of 140 mW is obtained. The corresponding pulse width and repetition frequency rate are 440 ns and 107.8 kHz, respectively. The stable pulsed laser operates at 1044.9, 1045.6 and 1048.5 nm, simultaneously. This work suggests that solvothermal synthesized WS₂ could be a promising SA to realize a simultaneously multi-wavelength laser operation.     

Morphology, Growth Process and Symmetry of {0001} Face on Yb：YAl3（BO3）4 Crystal

The {0001} face develops on the habit of self-frequency doubling laser crystal Yb: YAl3(BO3)4 (YbYAB) only under high growth rate condition, and its morphology is rough. To study the growth mechanism of {0001} face, we have observed the growth morphology on {0001} polishing section by atomic force microscopy (AFM). A series of AFM images captured in different growth durations on the {0001} polishing section reflect the crystal growth process. It is shown that the growth morphology on the {0001} polishing section was rough with many hillocks at the first growth stage, and it can become smooth finally, although the growth morphology on the {0001} face develoFed naturally on YbYAB crystal habit is always rough. On the smooth {0001} surface formed at the last growth stage, there aresome triangular pits. This fact is different from that of hillocks in most crystal growth morphologies. AFM can easilydistinguish the pits or hillocks on the surface, but differential interfere contrast microscopy (DIC) can not do. Theorientation of the triangular pits is just the opposite to the triangular {0001} faces. The chemical etching patternis also composed of this kind of triangular pits. These growth morphology and etching pattern of the {0001} facesshow 3m symmetry, but the point group of YbYAB crystal is 32. The symmetric contradiction between morphologyand point group does not exist for quartz, although whichsurface morphology we can distinguish the right form ormorphology we can not do. The reason for the symmetricand its point group is not known yet.has the same point group as YbYAB. From quartz {0001}left form of the crystal, but from YbYAB {0001} surfacecontradiction between YbYAB {0001} surface morphology and its point group is not known yet.     

Effect of symmetry reduction on the electronic transitions in polytypic GdAl3(BO3)4:Eu:Tb crystals

The existence of a recently described monoclinic phase (C2/c, Z = 8) (Beregi et al., 2012) in addition to the well-known Huntite type rhombohedral (R32) polytypic modification of the GdAl₃(BO₃)₄ (GAB) crystal at room temperature provides a unique possibility to investigate the incorporation of rare earth dopants into slightly modified crystal lattice by spectroscopic methods. In these characteristic GAB structures the dopant ions, e.g. Tb³⁺ or Eu³⁺, possess slightly different neighbor geometries and local symmetries. The Tb³⁺: ⁷F₆ → ⁵D₄ and Eu³⁺: ⁷F_0,1,2 → ⁵D_0,1,2 electronic transitions were successfully identified in the absorption spectra using polarization, concentration and temperature dependent measurements in both polytypic modifications. The positions of the investigated Tb lines are shifted by up to 10 cm⁻¹ due to symmetry changes. In addition, some of the Eu lines show splittings of about 4–30 cm⁻¹ as a consequence of the change of the local environment. From the room temperature absorption measurements some of the low energy crystal field levels of ⁷F and ⁵D states of the Eu³⁺ ions were successfully determined for both modifications.     

YAl3(BO3)4:TM (TM = Mn, Co, Cr) nanocrystals synthesis for laser operated nonlinear optics

An attempt to synthesize YAB matrices doped with cobalt, manganese, and chromium ions by means of the Pechini method for photo-induced nonlinear optics was performed. The best results were obtained for the Cr doped samples. It may be related with the fact that YAB:Cr main absorption peak is situated near the photo-inducing green second harmonics of Nd:YAG laser at 532 nm. It was established that after 600 s of samples illumination there was observed some maximum of the SHG. With the further treatment of the materials the SHG starts to decrease. The maximal enhancement was achieved at 150 K. After the switching off of the photo-inducing treatment the output SHG was relaxed to initial state during 2–3 min. Local increase of temperature due to heating did not exceed 6 K. For the Mn doped YAB NC the behavior is quite non-monotonic. The SHG changes are within the accuracy of the YAB NC NLO measurements. One can see two slight maxima at 200 and 800 s. At the same time Co suppress the output SHG, which may be caused by specific features of Co ions.     

Tunable coherent infrared generation near 2.5 microm from self-difference frequency mixing in YAl3(BO3)4:Nd3+

Idler generation from self-difference frequency mixing of the pump wave near 750 nm and the 1062-nm Nd3+ laser emission in the bifunctional laser and nonlinear optical YAl3(BO3)4:Nd3+ crystal was shown. The efficiency was 0.37%, and the infrared wavelength was tunable in the 2430-2600-nm range. New Sellmeier formulas that predict phase-matching polar angles for frequency conversion processes involving wavelengths up to 2600 nm were established.     

Synthesis and properties of magnetoresistive (La,Sr)MnO<Subscript>3</Subscript>-based glass-ceramic borate-matrix composites

Magnetic glass-ceramic borate-matrix composites containing micron-sized lanthanum strontium manganite grains have been prepared by ceramming amorphous La₂O₃-SrO-MnO _x -B₂O₃ materials at 800 and 900°C. The glass-ceramics had a magnetization of up to 48.7 A m²/kg in a magnetic field of 400 kA/m. Their relative magnetoresistance reached 6.2% at 290 K in a magnetic field of 80 kA/m and 16% at 77 K in a field of 160 kA/m.     

Polyspectral white light emission from Eu3+, Tb3+, Dy3+, Tm3+ co-doped GdAl3(BO3)4 phosphors obtained by combustion synthesis

Polycrystalline sub-micron-sized GdAl₃(BO₃)₄ phosphors co-doped with Eu³⁺, Tb³⁺, Dy³⁺ and Tm³⁺ have been prepared by combustion synthesis with urea. The phosphors have been characterised by X-ray diffraction, scanning electron microscopy, excitation and emission spectroscopy. The chromaticity co-ordinates and the colour temperatures of the fluorescence of the materials presented have been calculated and analysed with Commission Internationale l’Eclairage (CIE) programs and diagrams. Depending on the excitation wavelength, different colour temperatures of the light emitted can be achieved. Due to its polyspectral nature, the emitted light reveals a high colour rendering index.     

Temperature phase-matching properties for harmonic generation in GdCa4O(BO3)3 and Gd(x)Y(1-x)Ca4O(BO3)3

GdCa4O(BO3)3 has been found to have phase-matching points where the temperature variations of the phase-matching angles become zero for type-1 sum-frequency generation in the zx plane. We also found that the temperature sensitivities of the phase-matching conditions in the zx plane are different along the phi = 0 degrees and phi = 180 degrees directions in this material. In addition, the thermo-optic dispersion formula of this material that reproduces the temperature phase-matching properties of GdCa4O(BO3)3 and Gd(x)Y(1-x)Ca4O(BO3)3 is presented.     

Spectroscopic properties of HoAl3(BO3)4 single crystal

The Judd–Ofelt theory has been applied to analyze absorption spectra of Ho³⁺ ion in HoAl₃(BO₃)₄ measured in spectral range 300–700 nm at room temperature. The Judd–Ofelt spectroscopic parameters have been determined as: Ω₂ = 18.87 × 10⁻²⁰ cm², Ω₄ = 17.04 × 10⁻²⁰ cm², Ω₆ = 9.21 × 10⁻²⁰ cm². These parameters have been used to calculate radiative lifetimes and branching ratios of the luminescence manifolds. Three luminescent bands were found in the spectral range 450–700 nm ascribed to transitions from the ⁵F₅, (⁵F₄, ⁵S₂) and ³K₈ states to the ground state ⁵I₈. Experimental intensities of these luminescence transitions were compared with those calculated by using Judd–Ofelt theory and the system of kinetic equations for populations of starting luminescing states. Probabilities of radiativeless transitions were evaluated from this comparison.     

Optimal performance of NdAl3(BO3)4 nanocrystals random lasers

Resonant pumping associated with the influence of the quantum-defect between the excitation and the emitted laser photons allow optimal performance of neodymium ions (Nd³⁺) based random lasers (RLs), as demonstrated here for the first time. The RL emission at 1063.5 nm due to the Nd³⁺ transition ⁴F_3/2 → ⁴I_11/2 in a powder consisting of NdAl₃(BO₃)₄ nanocrystals, was investigated by exciting the powder at 690 nm, 750 nm, 810 nm, and 884 nm in resonance with the Nd³⁺ transitions from the ground state (⁴I_9/2) to the ⁴F_9/2, {⁴F_7/2,⁴S_3/2}, {⁴F_5/2,⁴H_9/2}, and ⁴F_3/2 states, respectively. Although the Nd³⁺ absorption cross-section at 884 nm is smaller than those centered at 810 and 750 nm, excitation at 884 nm, that is in resonance with the emitting level, provided the smaller excitation pulse energy threshold and the larger slope efficiency due to the lower quantum defect.     

Structure of medium temperature phase β-LaSc3(BO3)4 crystal

The compound β-LaSc₃(BO₃)₄ crystallizes in the rhombohedral with space group R32 and cell parameters a=9.819(3), c=7.987(1) Å, Z=3, V=666.5(3) Å³, Dc=3.80 g/cm³, λ(MoKα)=0.71067 Å, F(000)=708, final R=0.053. R_W=0.072 for 512 observed reflection with I≥3σ(I). The La atoms, Sc atoms and B atoms occupy trigonal prisms, octahedra and planar triangle of oxygen, respectively. The isolated LaO₆ trigonal prisms alternate along the c-axis with BO₃ triangle (B(1)) that are perpendicular to the c-axis. La³⁺ ions join by means of La-O-Sc(B)-O-La with the distance between La³⁺ ions being 6.263 Å. This structural characteristic will result in a weaker interaction between Nd³⁺ ions and a lower fluorescence concentration quenching effect.     

Single-crystal oxoborate (Pb3O)2(BO3)2WO4: Growth and characterization

An oxoborate, (Pb₃O)₂(BO₃)₂WO₄, has been prepared by solid-state reaction methods below 620 °C. Single-crystal XRD analysis shows that it crystallizes in the orthorhombic group Cmcm with a = 18.480(4) Å, b = 6.3567(13) Å, c = 11.672(2) Å, Z = 4. The crystal structure is composed of one-dimensional 1/∞ [Pb₃O]⁴⁺ chains formed by corner-sharing OPb₄ tetrahedra. BO₃ and WO₄ groups are located around the chains to hold them together via PbO bonds. The IR spectra further confirmed the presence of BO₃ groups. Furthermore we have performed theoretical calculations by employing the all-electron full potential linearized augmented plane wave (FP-LAPW) method to solve the Kohn Sham equations. Starting from our XRD data we have optimized the atomic positions by minimizing the forces. These are used to calculate the electronic band structure, the atomic site-decomposed density of states, electron charge density and the chemical bonding features. The calculated electronic band structure and densities of states suggest that this oxoborate possesses a wide energy band gap. The valence band maxima and the conduction band minima are located at Y point in the Brillouin zone resulting in a direct energy band gap of 2.3 eV using the local density approximation and 2.6 eV for the Engel–Vosko generalized gradient approximation. This compares well with our experimentally measured energy band gap of 2.9 eV. From our calculated electron charge density distribution, we obtain an image of the electron clouds that surround the molecules in the unit cell of the crystal. The chemical bonding features were analyzed and the substantial covalent interactions are observed between Pb and O, B and O and W and O atoms.     

Low-temperature-sintering and characterization of glass-ceramic composites

To meet the demands of high power and high-speed propagation of the signal for very large scale integration, a series of glass/ceramic composites were prepared using electronic ceramics process from borosilicate glass with Sr-celsian, which contains 30, 40, 50, 60, 70 wt% ceramic. The phase and microstructural evolution of the composites were characterized by XRD and SEM. The properties of the composites were also measured. Results show that the thermal expansion coefficient, dielectric constant and hardness of the composites increase with an increase content of Sr-celsian. However, the dielectric loss decreases with increasing Sr-celsian content. For the composites with ≧ 60 wt% Sr-celsian fired at 850–900°C, formation of α-quartz and cristobalite in the composites during the sintering process has bad effect on thermal expansion, but has little effect on the values of dielectric properties of the composites. The obtained composites exhibit low dielectric constant (5.2–5.8), low dielectric loss (⩽ 0.25%), low thermal expansion coefficient (4.4–6.2 × 10⁻⁶°C⁻¹) and low-temperature sintering behavior (⩽900 °C), which suit for electronic packaging field.     

Efficient and tunable continuous-wave diode-pumped Yb3+:Ca4GdO(BO3)3 laser

A Yb(3+):Ca(4)GdO(BO(3))(3) (Yb:GdCOB) crystal has been diode pumped for the first time to our knowledge. We obtained 47.5% slope efficiency at 6 degrees C, producing 191 mW of power at 1050 nm, with a 2.4% output coupler. Temperature does not significantly affect the laser performance: At room temperature we still obtained 180 mW of power for the same cavity. We achieved tunability of the Yb:GdCOB laser from 1035 to 1088 nm with a 1.7% output coupler and 100-nm tunability with a low-transmission output coupling (T = 0.03%).     

Growth,thermal and optical properties of Yb:GdYAl3(BO3)4 crystal

Single crystal of Yb:GdYAl₃(BO₃)₄(Yb:GdYAB) has been grown by the flux method. The structure of Yb:GdYAB crystal has been determined by X-ray diffraction analysis. The experiment show that the crystal has the same structure as that of YAl₃(BO₃)₄ crystal and its unit cell constants have been measured to be a = 9.30146 Å, c = 7.24164 Å, Vol = 542.59 Å³. The absorption and fluorescence spectrum of Yb:GdYAl₃(BO₃)₄ crystal have also been measured at room temperature. In the absorption spectra, there are two absorption bands at 938 nm and 974 nm, respectively, which is suitable for InGaAs diode laser pumping. In the fluorescence spectra, there are two fluorescence peaks at 992 and 1040 nm. The thermal properties of Yb:GdYAl₃(BO₃)₄ crystal have been studied for the first time. The thermal expansion coefficient along c-axis is almost 5.4 times larger than that along a-axis. The specific heat of the crystal has been measured to be 0.77 J/g °C at room temperature. The calculated thermal conductivity is 5.26 Wm⁻¹ K⁻¹ along a-direction.     

Structure, growth, and optical properties of TbAl3(BO3)4 single crystal

TbAl(3)(BO(3))(4) single crystal was grown from a K(2)Mo(3)O(10)-B(2)O(3) system using the top-seeded high temperature solution method (TSSG), 20 mm×9 mm×7 mm in size. The grown crystal was characterized by x-ray diffraction analysis showing that the crystal has a trigonal structure and the space group is R32 with lattice parameters of a = b = 9.293(13) ?, c = 7.249(6) ?. Faraday rotations of TbAl(3)(BO(3))(4) crystal were investigated at room temperature at wavelengths of 532, 633, and 1064 nm. Finally, the Verdet constants were measured at V = -108.8, -85.7, and -20.8 rad/mT for 532, 633, and 1064 nm, respectively.