New nonlinear-laser effects in YbVO4 crystal: Sesqui-octave stokes and anti-Stokes comb generation and the cascaded self-frequency “tripling” of χ(3)-Stokes components under a one-micron picosecond pumping

We report the experimental investigations of nonlinear-laser effects in vanadate YbVO₄ under a onemicron picosecond Nd³⁺:Y₃Al₅O₁₂ laser pumping. In this tetragonal host-crystal for Ln³⁺ lasants, for the first time, we excited more than one-and-a-half octave (≈11661 cm^?1) Raman-induced Stokes and anti-Stokes generation combs and observed a multistep cascaded parametric χ⁽³⁾ lasing in the deep-blue spectral region. All generation lines were identified and attributed to the SRS-promoting vibration mode of the crystal (ω_SRS ≈ 897 cm^?1). We classified the ytterbium vanadate as a promising material for Raman frequency converters, wideband χ⁽³⁾-nonlinear comb generators, and as a gain medium for solid-state lasers.     

Stimulated Raman scattering in natural crystals of SrSO4, BaSO4 and PbSO4: High-order Stokes and anti-Stokes generation with?single-wavelength UV, visible, and near-IR excitation, as?well?as cascaded up-conversion nonlinear �� (3)?�� (3) lasing effects under dual-wavelength picosecond collinear coherent pumping

Orthorhombic crystals of SrSO₄, BaSO₄, and PbSO₄, known as natural crystals celestine, barite, and anglesite, were found to be attractive ?? ⁽³⁾-active nonlinear optical materials. High-order Stokes and anti-Stokes picosecond generation that spans almost two octaves has been recorded with single-wavelength laser excitation in the UV, visible, and near-IR ranges. All recorded Raman induced lasing components were identified and attributed to the SRS-promoting vibration modes of the studied crystals (?? _SRS??999?cm^?1 for SrSO₄,?? _SRS??985?cm^?1 for BaSO₄ and ?? _SRS??977?cm^?1 for PbSO₄). Under dual-wavelength (?? _f1=1.06415???m + ?? _f2=0.53207???m) collinear coherent picosecond pumping several new manifestations of cascaded ?? ⁽³⁾??? ⁽³⁾ nonlinear up-conversion lasing effects were observed in BaSO₄ and SrSO₄ crystals. We classify all three studied sulfate crystals as promising SRS-active materials for Raman laser frequency converters and as efficient ?? ⁽³⁾-crystals that efficiently generate Stokes and anti-Stokes frequency combs, which can enable experiments of ultra-short pulse syntheses.     

Research on the defect structure and g factors for the tetragonal (CrO4)3− impurity center in ZrSiO4: Cr5+ crystal

ABSTRACT

The EPR g factors g// and g⊥ for the tetragonal (CrO₄)^3? impurity center in ZrSiO4: Cr⁵⁺ crystal are studied from the high-order perturbation formulas based on the two-mechanism (the crystal field and charge-transfer mechanisms) model. The studies indicate that differing from the tetragonally-elongated host (SiO4)^4- tetrahedron, the dominant defect structure of the substitutional (CrO₄)^3? tetrahedron is tetragonally- compressed with the ground state |d_z² due to the Jahn-Teller distortion. Furthermore, the agreement of g factors between calculation and experiment requires a small admixture of the first excited state |d_x²_?y² to the ground state |d_z² due to the vibrational motion of ligands, which leads a compressed (CrO₄)^3? tetrahedron to become a twinkling elongated one, These results are discussed.     

Efficient intracavity second-harmonic generation at 1.06 μm in a BiB3O6 (BIBO) crystal

We report, for the first time, efficient intracavity second-harmonic generation (SHG) at 1.06 μm in a non-linear optical crystal, BiB₃O₆ (BIBO), at a type-I phase-matching direction of (θ,ϕ)=(168.9°,90°), performed with a LD end-pumped cw Nd:YVO₄ laser. A cw SHG output power of 364 mW has been obtained using a 1.9-mm-thick BIBO crystal. The optical conversion efficiency was 12.2% and the corresponding effective intracavity SHG efficiency was determined to be 32.4%. It was found that the intracavity SHG efficiency is greater than that obtained with a type-II phase-matching KTiOPO₄ (KTP) crystal with a thickness of 3 mm. The effective non-linear optical coefficient (d_eff) ratio of BIBO to that of KTP, determined experimentally, is 1.23:1. Received: 7 May 2001 / Revised version: 6 July 2001 / Published online: 19 September 2001     

Compact diode-pumped Yb:YAl3(BO3)4 laser generating 14.0 W of continuous-wave and 8.5 W of pulsed output powers

An efficient compact diode-pumped Yb:YAl₃(BO₃)₄ laser operating at room temperature is demonstrated. Output powers of 14.0 and 8.5 W are generated in continuous-wave and passively Q-switched operation, respectively. Laser pulses of 262.8 μJ in energy and 8.1 ns in duration are obtained, the corresponding peak power amounting to 32.4 kW.     

Efficient 1.06 μm laser operation in an unprocessed Nd3+:BaGd2(MoO4)4 cleavage microchip

A 1.2 mm thick microchip cleaved from a 1.2 at.% Nd³⁺: BaGd₂(MoO₄)₄ crystal was used as the laser gain medium directly. The laser cavity mirrors were coated on the microchip without cutting and polishing. In the 1.06 μm quasi-CW laser operation, the microchip was pumped by a Ti:sapphire laser with a duty cycle of 10%, the threshold is 10 mW, and the slope efficiency is 50%. In the CW laser operation pumped by a diode laser, the threshold and slope efficiency are 140 mW and 33%, respectively. The results demonstrate that the unprocessed surfaces of the cleaved microchip have good enough flatness and parallelism for laser operation.     

Crystal-host Gd0.5Lu0.5VO4 for Ln3+-lasants: a new high-gain many-phonon χ(3)-active tetragonal vanadate—SRS spectroscopy and nonlinear-laser effects

We found that tetragonal Gd_0.5Lu_0.5VO₄??known as host-crystal for Ln³⁺-lasants??is an attractive optical material for Raman laser converters. We discovered and investigated its almost sesqui-octave Stokes and anti-Stokes lasing comb resulting from four SRS-promoting vibration modes in combination with cascaded and cross-cascaded many-phonon ??⁽³⁾-nonlinear interactions. Furthermore, estimations of the steady-state Raman gain coefficient have been performed.     

A New Rhodamine-Based “Off-On” Fluorescent Chemosensor for Hg (II) Ion and its Application in Imaging Hg (II) in Living Cells

A novel rhodamine derivative (Rh-C), synthesized by the reaction of rhodamine ethylenediamine and cinnamoyl chloride, was evaluated as a chemoselective Hg(2+) ion sensor. Addition of Hg(2+) to an ethanol aqueous solution of the Rh-C resulted in a color change from colorless to obvious pink color together with distinctive changes in UV-vis absorption spectrum and fluorescence spectrum. However, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. The interaction of Hg(2+) and sensor Rh-C was proven to adopt a 1:1 binding stoichiometry and the recognition process is reversible. The chemosensor displayed a linear response to Hg(2+) in the range of 0.4-5?μM with a detection limit of 7.4?×?10(-8)?M. The sensor Rh-C was also successfully applied to the imaging of Hg(2+) in HL-7702 cells.     

Superionic conducting glass: Glass formation and conductivity in the (AgI)x-(Ag3AsO4)5 − x system

Glassy compounds of the system (AgI-Ag₃AsO₄) were prepared by quenching the molten compound in liquid nitrogen. The glassy nature of the quenched samples were confirmed by X-ray. Conductivity studies were made on the pellets of these samples at different temperatures. The conductivity at 300 K of the glass of any particular composition is found to be higher than that of the polycrystalline sample of the same composition. The activation energy for migration of silver ions is found to be slightly higher in the case of glasses. The glass transition temperatures were evaluated from conductivity and DTA studies. The electronic conductivity of the glass of maximum conductivity, evaluated by Wagner's polarisation technique, is found to be much less than the total conductivity.     

Local defect structures and EPR studies on (FeO6)9− and (FeO4)5− clusters in YGG: Fe3+ system

The octahedral (FeO₆)^9? and tetrahedral (FeO₄)^5? clusters in yttrium gallium garnet (YGG): Fe³⁺ system are investigated based on the 252 × 252 complete energy matrices for d⁵ configuration ions in trigonal and tetragonal ligand fields, moreover, the EPR and optical spectra are made unified calculation. The results indicate that the defect structures around Fe³⁺ centres display expansion effects at different temperatures 4.2 and 295 K, and which are close to those in YIG garnet, respectively. Simultaneously, the defect structure parameters for Fe³⁺ centres in YGG are determined, and the relationship between the defect structure and the temperature has been discussed.     

Manifestation of an intermediate phase in a ferroelastic K3Na(CrO4)2:MnO 4 2− in raman and IR absorption spectra

In a broad temperature range of 4–300 K, we have performed a complex combined investigation of phase transitions in crystals of a ferroelastic K₃Na(CrO₄)₂:MnO ₄ ^2? using methods of Raman light scattering and IR light absorption. Considerable changes that we have observed in both Raman and IR spectra in the range of T ≈ 150 K testify to the occurrence of another phase transition that has not been observed before at this temperature. We have performed a group-theoretical analysis and compared its results with experimental spectra, which has allowed us to conclude that there are two phase transitions in this crystal, \(P\bar 3m1 \to C2/m \to C2/c\) , which occur at temperatures T _c1 ≈ 230 K and T _c2 ≈ 150 K, respectively.     

Condensation Product of 4-Methoxybenzaldehyde and Ethylenediamine: “Off-On” Fluorescent Sensor for Cerium(III)

The condensation product (L) of 4-methoxybenzaldehyde and ethylenediamine has been synthesised and characterised. L showed a 21 times enhancement in fluorescence intensity on interaction with Ce³⁺ in CH₃OH at λ_max?=?360 nm when excited with 270 nm photons. Metal ions K⁺, Na⁺, Al³⁺, Co²⁺, Hg²⁺, Cd²⁺, Ni²⁺, Zn²⁺, Mn²⁺, Mg²⁺ and Ca²⁺ do not interfere. The stoichiometry of binding and the binding constants were determined from spectroscopic data and found to be 1:1 and 10^4.8 M respectively. The detection limit was found to be 10^–5.2 M. The protonation/de-protonation of water molecules coordinated to Ce³⁺ was found to show interesting behaviour on the fluorescence of L:Ce³⁺.     

Nature of M-Ng interaction in the MNg 4 2+ (M = Cu, Ag and Au; Ng = He and Ne) molecules: ab initio calculations

Quantum chemical calculations of the structure and stability of MNg ₄ ²⁺ (M = Cu, Ag and Au; Ng = He and Ne) series at the CCSD(T) theoretical level are performed. The interaction mechanism is investigated using the natural bond orbital (NBO) and electron density analyses. The analyses of the electron density show the weak electrostatic interaction in the system.     

2-Methyl-4-oxo-N-(4-oxo-2-phenyl substituted-1,3-thiazolidin-3-yl)-3,4-dihydroquinazoline-5-carboxamides—A New Range of Fluorescent Whiteners: Synthesis and Photophysical Characterization

Fluorescent quinazolinones were synthesized form ethyl 2-methyl-4-oxo-3,4-dihydroquinazoline ?5-carboxylate intermediate. The photophysical properties of the compounds were evaluated in DMF solvent. The experimental absorption and emission of the compounds were compared with the vertical excitation and emission obtained Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD-DFT) computation. Application of the fluorescent compounds as a fluorescent brightening agent was tested on polyester fiber. Changes in the electronic transition, energy levels, and orbital diagrams of quinazolin-4(3H)-one analogues were investigated using the DFT computations and were correlated with the experimental spectral data. The experimental absorption and emission wavelengths are in good agreement with those predicted using the DFT and TD-DFT.     

Synthesis of a New Thermal and Photostable Reference Probe for Qf Measurement in Aqua: Water Soluble N,N′-bis-(2-Hydroxy-4-benzoic Acid)-3,4,9,10-perylenebis(dicarboximide)

N,N′-bis(2-hydroxy-4-benzoic acid)-3,4,9,10-perylenebis(dicarboximide) is synthesized from perylene 3,4,9,10-tetracarboxylic dianhydride and 4-amino-3-hydroxy benzoic acid in 90% yield. Together with the photostability the dye is also very stable thermally. The fluorescence quantum yield is measured as one, Q_f=1.The diimide dissolves in water at PH = 8 completely. The diimide is an ideal reference probe for fluorescence quantum yield measurements in 500–650 nm region and an attractive photosensitizer for the photoreactions occur in water.     

Nonlinear refractive indices in Yb3+-doped and undoped monoclinic double tungstates KRE(WO4)2 where RE=Gd, Y, Yb, Lu

The linear absorption bandgap in the ultraviolet and the nonlinear index n ₂ in near infrared were systematically measured in undoped and Yb³⁺-doped top-seeded solution-grown monoclinic double-tungstate KRE(WO₄)₂ (RE=Gd, Y, Yb, Lu) crystals. Anisotropic n ₂ nonlinear indices have been determined for E‖N _m and E‖N _p polarizations with the maximum nonlinear index n ₂ observed for the light polarized E‖N _m. Moreover, the value of the nonlinear response of particular crystals in this family is proportional to the ionic radius of the RE³⁺ ion.