Growth and optical properties of Er,Yb:YAl3(BO3)4 crystal

Single crystal of erbium, ytterbium-codoped yttrium aluminum tetraborate Er,Yb:YAl₃(BO₃)₄(Er,Yb:YAB) has been grown by the flux method. The absorption spectrum in the visible and NIR regions of Er,Yb:YAl₃(BO₃)₄ crystal are measured at room temperature and fluorescence spectrum of Er,Yb:YAl₃(BO₃)₄ crystal are also measured at room temperature, excited by 976 nm laser. Not only the strong NIR emission peaks located at 1548 nm was observed, but also the visible up-conversion luminescence has been found. The specific heat of the Er/Yb:YAB crystal at room temperature is 0.81 J/g °C.     

Growth and properties of UV nonlinear optical crystal ZnCd(SCN)4

A second-order nonlinear optical coordination crystal, zinc cadmium thiocyanate, ZnCd(SCN)₄ (ZCTC) was grown as a frequency doubler, emitting UV light. A large typical single crystal with dimensions up to 15×7×7 mm³ has been obtained by slow solvent-evaporation method for the first time. The infrared (IR) spectroscopy and X-ray powder diffraction (XRPD) of single crystals were performed at room temperature. The specific heat of the crystal has been measured to be 367.9 J/mol K at 300 K. The thermal expansion coefficients a- and c-oriented, have been measured to be −1.69×10⁻⁵ and 1.95×10⁻⁴ K⁻¹, respectively. The second harmonic generation (SHG) efficiency of ZCTC crystal is 51.6 times as high as that of urea reference, and the measured transmittance spectra from 190 to 3200 nm showed that the UV transparency cutoff occurs at 290 nm and the transmission is 73.22% at 380 nm. UV laser light of wavelength 380 nm has been achieved by the frequency doubling of a 760 nm laser diode at room temperature.     

Spectral properties of Tm:NaGd(MoO4)2 crystal

The Tm³⁺:NaGd(MoO₄)₂ crystal with dimensions of Φ 15 × 38 mm² was grown by Czochralski method. Polarized absorption and fluorescence spectra at room temperature were investigated. The absorption bands attributed to ³H₆ → ³H₄ transition have large absorption cross-sections, which are 3.99 × 10⁻²⁰ and 2.36 × 10⁻²⁰ cm² for σ- and π-polarization, respectively. The emission bands corresponding to the ³H₄ → ³H₆ transition are strong and broad with emission cross-sections of 1.33 × 10⁻²⁰ and 1.20 × 10⁻²⁰ cm² for σ- and π-polarization, respectively. The correlative full widths at half maximum are 35 nm for σ-polarization and 36 nm for π-polarization. The fluorescence lifetime for the ³H₄ → ³F₄ transition is 146 μs and the luminescent quantum efficiency is 76.8%.     

Larger Ba(NO3)2/Sr(NO3)2 crystal growth and solubility determination

The solubility of Ba(NO₃)₂ and Sr(NO₃)₂ crystals in aqueous solution from 25 to 65 °C has been determined by both an optical interferometer and a weight technique. A Mach-Zehnder interferometer was used for measuring the concentration distribution of Ba(NO₃)₂ and Sr(NO₃)₂ near the solid/liquid interface during crystal growth and dissolution. A fringe carrier technique was introduced to visualize more clearly the boundary layer and to solve the concentration distribution. Crystals were successfully grown with sizes larger than  mm by a temperature cooling method. The Ba_xSr_1−x(NO₃)₂ crystal was also nucleated and grown. The Raman spectra of Ba_xSr_1−x(NO₃)₂ indicate that the barium ions probably degrade the properties of Sr(NO₃)₂.     

Growth, thermal and spectroscopic characteristics of LiNd(WO4)2 crystal

Crystal growth, thermal and optical characteristics of LiNd(WO₄)₂ crystal have been investigated. The LiNd(WO₄)₂ crystal up to Ø15 × 32 mm³ has been grown by Czochralski technique. The hardness is about 5.0 Mohs’ scale. The specific heat at 50 °C is 0.42 J g⁻¹ K⁻¹. The thermal expansion coefficient for c- and a- axes is 1.107 × 10⁻⁵ and 2.104 × 10⁻⁵ K⁻¹, respectively. The absorption and fluorescence spectra and the fluorescence decay curve of LiNd(WO₄)₂ crystal were measured at room temperature. Some spectroscopic parameters such as the intensity parameters, the spontaneous transition probabilities, the fluorescence branching ratios, the radiative lifetimes and emission cross sections were estimated.     

Preparation, structure and luminescent properties of a new potassium yttrium borate K3Y3(BO3)4

A new yttrium borate compound K₃Y₃(BO₃)₄ has been obtained in the K₂O-Y₂O₃-B₂O₃ ternary system. Its structure, determined from single crystal X-ray diffraction data, shows that it belongs to space group P2₁/c with unit cell dimensions of a = 10.4667(16) Å, b = 17.361(3) Å, c = 13.781(2) Å and β = 110.548(8)°. The structure consists sheets of [Y₈B₈O₂₄]_∞ linked by out of sheet BO₃ groups and Y ions to form a three-dimensional framework. The luminescent properties of Eu³⁺ and Tb³⁺ doped K₃Y₃(BO₃)₄ materials have also been studied.     

Crystal growth and spectral properties of Pr:La2(WO4)3

Pr³⁺-doped La₂(WO₄)₃ single crystal with dimensions up to Ø 20 mm × 35 mm has been grown by the Czochralski method. The structure of the Pr³⁺:La₂(WO₄)₃ crystal was determined by the X-ray powder diffraction and the Pr³⁺ concentration in this crystal was determined. The absorption and fluorescence spectra of Pr³⁺:La₂(WO₄)₃ crystal were measured at room temperature, and the fluorescence lifetime of main emission multiplets were estimated from the recorded decay curves. The spectral properties related to laser performance of the crystal were evaluated.     

Crystal growth of Nd: NaLu(WO4)2

Nd: NaLu(WO₄)₂ single crystals have been grown by the top seeded solution growth (TSSG) method. The peaks shown in the X-ray powder diffraction pattern were assigned. The crystal belongs to the space group of I4₁/a and the unit-cell parameters were calculated as a = b = 5.168 Å, c = 11.174 Å, V = 298.46 Å³. It is a tetragonal scheelite-like single crystal. The DSC (differential scanning calorimeter) curve proved that the as-grown crystal had a glass transition at the temperature range of 733.8 °C-781.4 °C which was lower than its melting point at 1149.3 °C. The absorption and fluorescence spectra were measured at room temperature.     

Growth and spectral properties of Cr:KAl(MoO4)2 crystal

The Cr³⁺:KAl(MoO₄)₂ single crystal was grown by top seeding solution growth method (TSSG). Based on the absorption and emission spectra, the crystal field strength Dq, the Racah parameters B and C, the effective phonon energy ?ω and the Huang-Rhys factor S were calculated: Dq = 1494.8 cm^− 1, B = 585.5 cm^− 1 and C = 3049 cm^− 1, ?ω = 373.8 cm^− 1 and the Huang-Rhys factor S = 3.74, respectively. The value Dq/B = 2.55 indicates that Cr³⁺ ion occupies the strong crystal field site in KAl(MoO₄)₂ crystal. A comparison of crystal field parameters for Cr³⁺:KAl(MoO₄)₂ with other Cr³⁺-doped crystals was presented. The results of spectral measurement show that Cr³⁺:KAl(MoO₄)₂ may be a potential candidate for broadband laser applications.     

Growth and spectral properties of Er:NaGd(WO4)2 crystal

A high optical quality Er³⁺-doped NaGd(WO₄)₂ single crystal with dimensions of ∅18 × 50 mm³ has been grown using the Czochralski method. The structure of the grown crystal was proved by X-ray powder diffraction. The accurate concentration of Er³⁺ ion in the crystal was measured. The absorption spectra, fluorescence spectra and fluorescence lifetime of the crystal were measured at room temperature. Green up-conversion luminescence has been observed when the crystal is excited at 965 nm.     

Growth and characterization of non-linear optical crystal Cd3Zn3B4O12

Cd₃Zn₃B₄O₁₂ polycrystals were synthesized by solid-state and wet chemical reaction methods. Cd₃Zn₃B₄O₁₂ single crystals with millimeter grade were grown from the self-flux B₂O₃ (Cd:Zn:B = 1:1:1.5); and larger crystals were obtained from the PbO-0.85PbF₂ fluxes easily. As-grown crystals were characterized by differential scanning calorimetry and thermogravimetric, X-ray diffraction, infrared and Raman spectral analysis, respectively. The non-linear optical coefficient of the Cd₃Zn₃B₄O₁₂ crystal is 2.6 times as large as that of KH₂PO₄ crystal. Chemical etching shows that this crystal is very stable in neutral solution and not hygroscopic in air at room temperature.     

Waveguiding properties of pulsed-laser deposition Ca4GdO(BO3)3 thin films

Waveguiding properties of stoichiometric Ca₄GdO(BO₃)₃ (GdCOB) thin films deposited on quartz substrates by the pulsed-laser deposition (PLD) technique are reported. The optical properties and the anisotropy of the obtained thin films are investigated using the prism-coupling technique. Refractive indices (n_x=1.666, n_y=1.673 and n_z=1.680 at 632.8 nm) were, respectively, determined from the transverse electric (TE) and the transverse magnetic (TM) mode excitations. These values are found to be 3% lower than those of the bulk material, which is likely due to the structural and morphological features of the deposited GdCOB films.     

Negative thermal expansion in Th2O(PO4)2

High temperature X ray diffraction performed on recently discovered orthorhombic Th₂O(PO₄)₂ shows a continuous linear thermal contraction (−1.6 × 10⁻⁶ °C⁻¹) in 20–600 °C range and a near-zero expansion at higher temperatures resulting from a dual structural deformation involving oxygen oscillations and inter-cations repulsions. Although similar mechanisms were observed in isotypic Zr₂O(PO₄)₂ (+1.5 × 10⁻⁶ °C⁻¹) and U₂O(PO₄)₂ (−1.4 × 10⁻⁶ °C⁻¹), those observed in Th₂O(PO₄)₂ are particularly intense because of the high ionic radius of tetravalent thorium.     

Ag-catalyzed synthesis of europium borate Eu(BO2)3 nanowires, growth mechanism and luminescent properties

Eu(BO₂)₃ nanowires with diameters of 10-20 nm were fabricated through direct sintering Eu(NO₃)₃·6H₂O and H₃BO₃ with Ag as catalyst. The result of X-ray diffraction (XRD) indicated that the nanowire was single-crystalline with body-centered monoclinic structure. Based on the fact that Ag nanoparticles attached to the tips and middles of nanowires, a vapor-liquid-solid (VLS) growth mechanism of the Eu(BO₂)₃ nanowires is proposed. Three well-defined stages have been clearly identified during the process: Ag-Eu-B-O cluster process, crystal nucleation, and axial growth. The photoluminescence characteristics under UV excitation were investigated. The dominated Eu³⁺ orange-red emission corresponding to the magnetic dipole transition ⁵D₀ → ⁷F₁ is centered at 591 nm, indicating that Eu³⁺ is located at high symmetry crystal field with inversion center.     

Growth and characterization of Ca5(BO3)3F fiber crystals, a new nonlinear optical material for UV light generation

For the first time, Ca₅(BO₃)₃F (CBF) fiber crystals were grown by the micro-pulling down technique from LiF-based flux. Regular and transparent fibers were obtained with good optical quality. Characterization by Raman spectroscopy and EDX microprobe showed fibers compositionally homogeneous. The specific heat capacity of the fibers was measured indicating a laser damage threshold slightly lower, at room temperature, than for crystals belonging to the related rare earth calcium oxoborate family.     

Crystal structure and spectroscopic studies of NaGd(PO3)4

Single crystals of gadolinium–sodium polyphosphate NaGd(PO₃)₄ were grown for the first time using a flux method and characterized by X-ray diffraction. This phosphate crystallizes in a monoclinic system with P2₁/n space group and with the following unit-cell dimensions: a = 9.767(3) Å, b = 13.017(1) Å, c = 7.160(2) Å, β = 90.564(5)°, V = 910.3(4) Å³ and Z = 4. The crystal structure was solved from 3451 X-ray independent reflections with final R(F²) = 0.0219 and R_w(F²) = 0.056 refined with 164 parameters (). The atomic arrangement can be described as a long chain polyphosphate organization. Two infinite (PO₃)∝ chains with a period of eight tetrahedra run along the [0 1 1] direction. The structure of NaGd(PO₃)₄ consists of GdO₈ polyhedra sharing oxygen atoms with phosphoric group PO₄. Each Na⁺ ion is bonded to eight oxygen atoms.     

BaZr(BO3)2: a non-centrosymmetric dolomite-type superstructure

The investigation of the ternary phase diagram for BaOZrO₂B₂O₃ has allowed single crystals to be grown by the flux method with formula BaZr(BO₃)₂. As this composition has been already announced in the literature, but without any structural data, the structure of BaZr(BO₃)₂ has been solved using X-ray data collected on a Kappa CCD diffractometer.This borate crystallizes in the trigonal symmetry with non-centrosymmetric space group R3c (no. 161): a=b=5.167(1) Å and c=33.913(7) Å; Z=6. The structure derived from the dolomite-type with a doubling of the c parameter. Along the c-axis, alternated layers of Ba atoms and Zr atoms are separated by planes of BO₃ groups. BaO₆ and ZrO₆ octahedra so formed are linked by their corners and each Ba(Zr) octahedron is linked to six Zr(Ba) octahedra and to six borate groups. The small deviation from centrosymmetry is attested by considering refinement agreement for the (weak) reflections (h k l) with odd value of l, and positive response of the powder second harmonic generation (SHG) test.A new J.C.P.D.S.-I.C.D.D. card is proposed for this compound.     

Growth, linear and nonlinear optical and, laser damage threshold studies of organometallic crystal of MnHg(SCN)4

Single crystals of bimetallic MnHg(SCN)₄ (abbreviated as MMTC) are grown by slow cooling method and the second and third order optical nonlinearities are investigated by Kurtz and Perry powder SHG test and single beam Z-scan technique respectively. The influences of SCN ligand in modifying the NLO properties are discussed and the results are compared with other organometallic crystals. The nonlinear refractive index, absorption coefficient and third order susceptibility are estimated to be −1.88 × 10⁻¹¹ cm²/W, 8.65 × 10⁻⁶ cm/W and 6.58 × 10⁻⁹ esu, respectively. The optical absorption of MMTC single crystal was recorded and the corresponding direct band gap is found to be 4.2 eV. The phase matching and laser induced damage threshold studies are also carried out. The FT-IR and photoluminescence spectroscopic techniques were employed to identify the composition and luminescence nature of the crystal.     

Growth and optical characterizations of (Ba0.32Sr0.68)5Nb4O15 crystal

(Ba_0.32Sr_0.68)₅Nb₄O₁₅ crystal with sizes of Ø 17 × 35 mm was grown successfully by Czochralski technique method. The thermal anisotropy was discussed. The principal coefficients of thermal expansion along (100), (010), (001) directions were precisely measured to be 1.308 × 10^− 5, 1.288 × 10^− 5, 1.478 × 10^− 5 K^− 1, respectively. Its optical transparency range has been measured and found to span from 323 to 5500 nm. The bands present in the IR spectra were identified and assigned to the corresponding vibration modes of NbO₆ anions.     

Multi-wavelength continuous-wave laser operation of Yb:Ca3Gd2(BO3)4 disordered crystal

The diode-pumped multi-wavelength continuous-wave laser operation of the disordered Yb:Ca₃Gd₂(BO₃)₄ crystal was firstly investigated in this paper. The simultaneous emission wavelengths varied from 2 to 5 in the range from 1045.4 to 1063.6 nm with the change of the absorbed pump power and crystal length. An output power of 1.4 W was obtained with four-wavelength emission, corresponding to an optical-optical slope efficiency of 23.7%. Five-wavelength emission at 1049.4, 1051.3, 1053.4, 1055.6 and 1057.4 nm was realized under the output power of 1.0 W. The absorption behavior of Yb:Ca₃Gd₂(BO₃)₄ have also been measured.