Red,blue and green visible lasers are more attractive with the development of the science and technology.Self frequency doubling is an important approach to realize visible lasers.For self frequency doubling,the basic...Red,blue and green visible lasers are more attractive with the development of the science and technology.Self frequency doubling is an important approach to realize visible lasers.For self frequency doubling,the basic requests are high figure of merit(FOM),high damage threshold,good chemical stability and mechanical properties.Perfection and growth characters are also important for a practical SFD crystal. In recent years,the discovery of rare earth calcium oxyborates has resulted in the renewal in the field of SFD crystal.ReCaO(BO 3) 3(ReCOB)is a new type of novel nonlinear optical crystals which is nearly congruently melt and can be grown with Czochralski method.ReCOB crystals possess high nonlinear coefficients and damage thresholds.They are non hydroscopic and easy cutting and polishing.They belong to monoclinic with point group m and space group cm.The strong anisotropy originated from the low symmetry makes the measurement and application of the crystal more complicated.More than half of naturally existed crystals belongs to low symmetry,consequently,the research on the nonlinear and anisotropic laser optical properties are not only important for ReCOB crystal,but also useful for the applications of other low symmetry crystals.展开更多
A novel coordination polymer [Nd2（PDB）2（CH3COO）2（H2O）3] （H2PDB = pyridine3,4-dicarboxylic acid） has been synthesized by the reaction of Nd（CH3COO）3 with pyridine3,4-dicarboxylic acid under hydrothermal condi...A novel coordination polymer [Nd2（PDB）2（CH3COO）2（H2O）3] （H2PDB = pyridine3,4-dicarboxylic acid） has been synthesized by the reaction of Nd（CH3COO）3 with pyridine3,4-dicarboxylic acid under hydrothermal conditions. Elemental analysis, IR spectra and X-ray crystal structure analysis were carried out to determine the composition and crystal structure of the title complex which belongs to the triclinic system, space group P^-1 with a = 6.9409（14）, b = 7.5497（15）, c = 22.530（5）A, α = 84.79（3）, β = 88.15（3）, γ= 75.55（3）^o, C18H18N2O15Nd2, Mr = 790.82, Z = 2, V = 1138.5（4） A^3, Dc = 2.307 g/cm^3,μ = 4.593 mm^-1, -6≤h≤8, -5≤k ≤8, -26≤l≤ 26, F（000） = 760, Rint = 0.0298, R= 0.0314 and wR= 0.0695 （I〉 2σ（I））. Nd（1） and Nd（2） are linked into zigzag chains by carboxylate groups of acetate with interesting μ3-η^2：η^2 fashion. The zigzag chains are bridged by PDB to form a 2D framework, and a 3D supramolecular network is further constructed via π-π stacking.展开更多
A diode-end-pumped electro-optic (EO) Q-switched adhesive-free bond composite Nd:YVO4 laser operating at a repetition rate of 200 kHz is reported.A pair of RbTiOPO4 (RTP) crystals are used as a high repetition EO Q-sw...A diode-end-pumped electro-optic (EO) Q-switched adhesive-free bond composite Nd:YVO4 laser operating at a repetition rate of 200 kHz is reported.A pair of RbTiOPO4 (RTP) crystals are used as a high repetition EO Q-switch.At the repetition rate of 200kHz,the maximum average output power of 11.8 W at wavelength 1064 nm and full width at half maximum of pulses of 16.65ns are achieved at an incident pump power of 27 W,corresponding to an optical conversion efficiency of 43.7% and a slope efficiency of 44.6%,respectively.To the best of our knowledge,this is the highest repetition rate reported on the EO Q-switched laser by using RTP crystals.展开更多
The absorption and emission spectra of the YVO4 single crystal co-doped with 1 at.% Nd^3＋ and 1 at.% Yb^3＋ are investigated. The efficient Nd^3＋ → Yb^3＋ energy transfer and the back transfer （Yb^3＋ → Nd^3＋） ...The absorption and emission spectra of the YVO4 single crystal co-doped with 1 at.% Nd^3＋ and 1 at.% Yb^3＋ are investigated. The efficient Nd^3＋ → Yb^3＋ energy transfer and the back transfer （Yb^3＋ → Nd^3＋） are observed at room temperature. The fluorescence lifetime of the 4F3/2 level of Nd^3＋ in Nd,Yb：YVO4 is measured under 808 nm laser light excitation. The efficiency of Nd^3＋ → Yb^3＋ energy transfer in YVO4 is determined to be about 34%.展开更多
We present a laser-diode-pumped passively mode-locked femtosecond disordered crystal laser by using Nd：CaGdAI04 （Nd：CGA） as the gain medium. With a pair of SF6 prisms to control the dispersion compensation, laser ...We present a laser-diode-pumped passively mode-locked femtosecond disordered crystal laser by using Nd：CaGdAI04 （Nd：CGA） as the gain medium. With a pair of SF6 prisms to control the dispersion compensation, laser pulses as short as 850fs at 1079nm are obtained with a repetition rate of 124.6 MHz. The measured threshold pump power is 1.45 W. A maximum average output power of 122mW is obtained under the pump power of 5.9 W. These results show that Nd：CGA could be a promising laser medium for generating femtosecond ultrashort pulse at about 1 μm.展开更多
We have developed a Nd:YAP single crystal Aber laser with linearly polarised light output at 1.0795μm.The laser is 100μm in diameter and operated with a threshold of 6.65mW.The slope efficiency is 12.9%.
The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction （XRD）, differential scanning calorimeter （DSC）, and transmission...The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction （XRD）, differential scanning calorimeter （DSC）, and transmission electron microscopy （TEM）.The results indicated that the as-cast Nd60Fe20Al10Ni10-xYx（X=-0, 2） amorphous alloys were fabricated with some quenched-in crystals, which could be restrained by Y. With the effect of yttrium, both the crystallization temperature and exothermic peak shifted to higher temperatures, illustrating that the thermal stability could be improved. The addition of Y changed the crystallization process and final crystallization results. Moreover, the crystallites in the amorphous matrix became more homogeneous and smaller. Meanwhile, Y was useful for the passivation of oxygen in chemistry and restrained the negative effect of oxygen. The activation energies of the start of crystallization and peaking were 1.21 and 1.16 eV, respectively, according to the Kissinger equation.展开更多
This paper reports the growth, X-ray diffraction and spectroscopy of Nd3＋：Sr3Gd2（BO3）4 crystal. A Nd3＋：Sr3Gd2（BO3）4 crystal with dimensions of φ20 × 45 mm3 has been grown by the Czochralski method. Nd3＋...This paper reports the growth, X-ray diffraction and spectroscopy of Nd3＋：Sr3Gd2（BO3）4 crystal. A Nd3＋：Sr3Gd2（BO3）4 crystal with dimensions of φ20 × 45 mm3 has been grown by the Czochralski method. Nd3＋：Sr3Gd2（BO3）4 crystal belongs to the orthorhombic system, space group Pnma （D2h） with a = 0.7401, b = 1.604 and c = 0.8755 nm. The absorption and emission spectra of Nd3＋：Sr3Gd2（BO3）4 were investigated. The absorption cross section oa is 3.11 × 10^-20cm2 at 808 nm. The absorption transition at 808 nm has an FWHM of 14 nm. The luminescence lifetime τf is 51.7 μs. The emission cross section oc at 1064 nm wavelength is 1.09 × 10^-19 cm2.展开更多
The neodymium tungstate single crystals Nd-2(WO4)(3) were grown using the Czochralski method. The energy level scheme of Nd3+, was obtained through the spectral measurement. The upconversion luminescence of the crysta...The neodymium tungstate single crystals Nd-2(WO4)(3) were grown using the Czochralski method. The energy level scheme of Nd3+, was obtained through the spectral measurement. The upconversion luminescence of the crystals at 457 and 657 nm, corresponding to the (D5/2-->I11/2)-D-4-I-4 and (2)G(7/2)-->I-4(9/2) transitions, respectively, excited by 808 nm of a laser diode, was observed at room temperature. The fluorescence intensity and the excitation light power have a linear relationship at 457 nm and a quadratic relationship at 657 nm.展开更多
Amorphous （Nd,Pr）13Fe80Nb1B6 ribbons were crystallized at 670-730°C for 5-25 min to study the effects of isothermal crystallization on their behavior and magnetic properties. XRD results indicate that the isoth...Amorphous （Nd,Pr）13Fe80Nb1B6 ribbons were crystallized at 670-730°C for 5-25 min to study the effects of isothermal crystallization on their behavior and magnetic properties. XRD results indicate that the isothermal incubation time is 12, 5, and less than 5 min at 670, 700, and 730°C, respectively. High coercivities, with the maximum value of iHc = 1616 kA/m at 700°C for 19 min, measured by a physical property measurement system, are obtained in the crystallized ribbons. This is mainly attributed to the addition of Pr and Nb, because Pr2Fe14B has a higher anisotropic field than Nd2Fe14B, and Nb enriched in the grain boundary regions can not only reduce the exchange-coupling effects among hard grains, but also impede grain growth during the crystallization process. In addition, it should also be related to the characteristics of the furnace that the authors designed.展开更多
The passively Q-switched and mode-locked（QML） characteristics in a diode-pumped Nd∶GdVO4 laser with Cr4+∶YAG saturable absorbers have been demonstrated. A maximum average output power of 710mW has been obtained ...The passively Q-switched and mode-locked（QML） characteristics in a diode-pumped Nd∶GdVO4 laser with Cr4+∶YAG saturable absorbers have been demonstrated. A maximum average output power of 710mW has been obtained in the QML laser. The maximum energy of a single Q-switched pulse is 52.5μJ, with the corresponding pulse width of 30ns and the peak power of 1.75kW, at the incident pump power of 7.75W. The repetition rates of the Q-switched envelope and the mode-locked laser pulse are 16.7kHz and 680MHz, respectively.展开更多
The title complexes （LnL3 （HL） （H2O） ]2· 2EtOH·2H2O （Ln= Nd （1）, La （2）, HL=adamantanecarboxylic acid） were prepared and determined by single-crystal X-ray diffraction. Both complexes crystallize ...The title complexes （LnL3 （HL） （H2O） ]2· 2EtOH·2H2O （Ln= Nd （1）, La （2）, HL=adamantanecarboxylic acid） were prepared and determined by single-crystal X-ray diffraction. Both complexes crystallize in triclinic system with space group P 1^-, cell parameters are： complex （1） a = 1.0556（2） nm, b =1.4913（3） nm, c = 1.4920（3） nm, a = 106.26 （3）°, β=93.51（3）°, γ=97.23（3）°, V=2.2253 （5） nm^3, Dcal=1.409 g · cm^-3, Z = I , F （ 000 ） = 990, μ（Mo Kα） = 1. 225 mm^-1, M, = 1884.50; complex （2） a = 1.0453（2） nm, b = 1.4971（3）nm, c = 1.5052（3） nm, α = 106.07（3）°, β =93.58 （3）°, γ=97.56（3）°, V=2.2391（5）nm^3, Dcal= 1.397 g·cm^-3, Z = 1, F（000） =984, μ（Mo Kα） = 1.015 mm^-1, Mr= 1877.88. The final R and wR are 0. 0396 and 0. 1062 for 8589 （1 ≥ 2σ （I）） observed reflections for complex （1）, 0.0505 and 0. 1344 for 8417 （ 1 ≥ 2σ （1） ） observed reflections for complex （2）, respectively. The crystals are consisted of a binuelear molecule. The coordination geometry of the Ln（ Ⅲ ） ion can be described as trieapped trigonal prism.展开更多
The reaction of NdCl_3 with lithium methylnaphthalene in 1:2 mole ratio in THF generates black powder. The powder reacts with cyclooctatetraene(COT)in THF to form the title complex.[Li(THF)_4Nd(C_8H_8)_2]· 2THF c...The reaction of NdCl_3 with lithium methylnaphthalene in 1:2 mole ratio in THF generates black powder. The powder reacts with cyclooctatetraene(COT)in THF to form the title complex.[Li(THF)_4Nd(C_8H_8)_2]· 2THF crystallizes in the monoclinic space group P2/c with unit-cell dimensions a=1.7858(7)nm, h=1.3243(4)nm,c=1.8086(6)nm.β=106.52(4)°,V=4.10 nm^3 and D_c=1.268 g/cm^3 for Z=4. F(000)=1660,R=0.0774,R_n=0.0733.The complex consists of discrete ion-pair and two THF molecules adduct.In the anion,the neodymium atom is coordinated by two COT rings.The structure of the cation shows that the lithium atom is attached with THF molecules only.展开更多
The Nd^3＋ 3.2% （atom fraction）：KGd（WO4）2 crystal was grown by Kyropoulos method. The absorption spectrum and fluorescence spectrum of Nd^3 ＋ ： KGW crystal were measured. The absorption cross sections at 808 nm...The Nd^3＋ 3.2% （atom fraction）：KGd（WO4）2 crystal was grown by Kyropoulos method. The absorption spectrum and fluorescence spectrum of Nd^3 ＋ ： KGW crystal were measured. The absorption cross sections at 808 nm（0. 6799 × 10^-20 cm^2） were calculated, and the output wavelength of fluorescence is 1064 and 1351 nm. The diode-pumped laser was operated both in the free-running and passively Q-switched operating modes. The maximum laser output（1064 nm） is 326 mW with 62.7 % slope efficiency when input energy is 900 mW. The beam quality factor M^2 ≈ 1.1. The green light of 532 nm is obtained in frequency doubling operation. The laser is passively Q-switched by using Cr^4＋ ：LuAG as saturable absorber. The pulse width is 170 ns at repetitive frequency of 15 kHZ.展开更多
The neodymium ions doped gadolinium vanadate (Nd∶GdVO_4) single crystals were successfully grown by Czochralski method. Chemical etching technique was used to reveal the dislocation structure of the crystals. An aver...The neodymium ions doped gadolinium vanadate (Nd∶GdVO_4) single crystals were successfully grown by Czochralski method. Chemical etching technique was used to reveal the dislocation structure of the crystals. An average dislocation density of (100) plane is 600 pits/mm 2. The crystal-morphology can be used to determine crystal orientation accurately with simple optical method.展开更多
The Nd^3＋：LiGd（WO4） 2 crystal with dimensions of 25mm×28mm×16mm was grown by the top-seeded solution growth method from the 60 mol% Li2W2O7 flux. LiGd（WO4） 2 crystallizes in the tetragonal system with ...The Nd^3＋：LiGd（WO4） 2 crystal with dimensions of 25mm×28mm×16mm was grown by the top-seeded solution growth method from the 60 mol% Li2W2O7 flux. LiGd（WO4） 2 crystallizes in the tetragonal system with space group I41/a（C4h^6） and cell parameters： a = 5.1986 and c = 11.2652A. The hardness is about 5.0 Mohs＇ scale. The specific heat is 0.40 J·g^-1·K^-1 at 50 oC. The thermal expansion coefficients for a-and c-axes are 1.314×10^-5 and 2.052×10^-5 K^-1,respectively. The room-temperature polarized absorption and emission spectra and the fluorescence decay curve was measured. The parameters of oscillator strengths,the spontaneous transition probabilities,the fluorescence branching ratios,the radiative lifetimes,and the emission cross sections have been investigated based on Judd-Ofelt theory and Füchtbauer-Ladenburg method. The absorption cross-section is 5.19×10^-20 cm^2 at 805 nm for π-polarization and its line width is 15 nm; the emission cross section is 1.726×10^-19 cm^2 at 1060.5 nm for π-polarization. The fluorescence and radiative lifetimes are 86 and 158 μs,respectively. The fluorescence quantum efficiency is 54.43%.展开更多
X-ray powder diffraction, resistivity and magnetization studies have been performed on polycrystalline Nd（FexMn1-x）2Si2 （0≤x 〈 1） compounds which crystallize in a ThCr2Si2-type structure with the space group 14/...X-ray powder diffraction, resistivity and magnetization studies have been performed on polycrystalline Nd（FexMn1-x）2Si2 （0≤x 〈 1） compounds which crystallize in a ThCr2Si2-type structure with the space group 14/mmm. The field-cooled temperature dependence of the magnetization curves shows that, at low temperatures, NdFe2Si2 is antiferromagnetic, while the other compounds show ferromagnetic behaviour. The substitution of Fe for Mn leads to a decrease in lattice parameters a, c and unit-cell volume V. The Curie temperature of the compounds first increases, reaches a maximum around x=0.7, then decreases with Fe content. However, the saturation magnetization decreases monotonically with increasing Fe content. This Fe concentration dependent magnetization of Nd（FexMn1-x）2Si2 compounds can be well explained by taking into account the complex effect on magnetic properties due to the substitution of Mn by Fe. The temperature＇s square dependence on electrical resistivity indicates that the curve of Nd（Fe0.6Mn0.4）2Si2 has a quasi-linear character above its Curie temperature, which is typical of simple metals.展开更多
文摘Red,blue and green visible lasers are more attractive with the development of the science and technology.Self frequency doubling is an important approach to realize visible lasers.For self frequency doubling,the basic requests are high figure of merit(FOM),high damage threshold,good chemical stability and mechanical properties.Perfection and growth characters are also important for a practical SFD crystal. In recent years,the discovery of rare earth calcium oxyborates has resulted in the renewal in the field of SFD crystal.ReCaO(BO 3) 3(ReCOB)is a new type of novel nonlinear optical crystals which is nearly congruently melt and can be grown with Czochralski method.ReCOB crystals possess high nonlinear coefficients and damage thresholds.They are non hydroscopic and easy cutting and polishing.They belong to monoclinic with point group m and space group cm.The strong anisotropy originated from the low symmetry makes the measurement and application of the crystal more complicated.More than half of naturally existed crystals belongs to low symmetry,consequently,the research on the nonlinear and anisotropic laser optical properties are not only important for ReCOB crystal,but also useful for the applications of other low symmetry crystals.
基金Project supported by the National Natural Science Foundation of China (No. 20671064)Foundation of Education Committee of Liaoning Province (No. 2005336)
文摘A novel coordination polymer [Nd2（PDB）2（CH3COO）2（H2O）3] （H2PDB = pyridine3,4-dicarboxylic acid） has been synthesized by the reaction of Nd（CH3COO）3 with pyridine3,4-dicarboxylic acid under hydrothermal conditions. Elemental analysis, IR spectra and X-ray crystal structure analysis were carried out to determine the composition and crystal structure of the title complex which belongs to the triclinic system, space group P^-1 with a = 6.9409（14）, b = 7.5497（15）, c = 22.530（5）A, α = 84.79（3）, β = 88.15（3）, γ= 75.55（3）^o, C18H18N2O15Nd2, Mr = 790.82, Z = 2, V = 1138.5（4） A^3, Dc = 2.307 g/cm^3,μ = 4.593 mm^-1, -6≤h≤8, -5≤k ≤8, -26≤l≤ 26, F（000） = 760, Rint = 0.0298, R= 0.0314 and wR= 0.0695 （I〉 2σ（I））. Nd（1） and Nd（2） are linked into zigzag chains by carboxylate groups of acetate with interesting μ3-η^2：η^2 fashion. The zigzag chains are bridged by PDB to form a 2D framework, and a 3D supramolecular network is further constructed via π-π stacking.
基金Supported by the Science and Technology Department Project of Jilin Province under Grant Nos 2010PT and 20100355.
文摘A diode-end-pumped electro-optic (EO) Q-switched adhesive-free bond composite Nd:YVO4 laser operating at a repetition rate of 200 kHz is reported.A pair of RbTiOPO4 (RTP) crystals are used as a high repetition EO Q-switch.At the repetition rate of 200kHz,the maximum average output power of 11.8 W at wavelength 1064 nm and full width at half maximum of pulses of 16.65ns are achieved at an incident pump power of 27 W,corresponding to an optical conversion efficiency of 43.7% and a slope efficiency of 44.6%,respectively.To the best of our knowledge,this is the highest repetition rate reported on the EO Q-switched laser by using RTP crystals.
基金Project supported by the National Natured Science Foundation of China （Grant No 60438020）.
文摘The absorption and emission spectra of the YVO4 single crystal co-doped with 1 at.% Nd^3＋ and 1 at.% Yb^3＋ are investigated. The efficient Nd^3＋ → Yb^3＋ energy transfer and the back transfer （Yb^3＋ → Nd^3＋） are observed at room temperature. The fluorescence lifetime of the 4F3/2 level of Nd^3＋ in Nd,Yb：YVO4 is measured under 808 nm laser light excitation. The efficiency of Nd^3＋ → Yb^3＋ energy transfer in YVO4 is determined to be about 34%.
基金Supported by the National Key Basic Research Program of China under Grant No 2013CB922402the International Joint Research Program,and the National Natural Science Foundation of China under Grant Nos 61210017 and 11434016
文摘We present a laser-diode-pumped passively mode-locked femtosecond disordered crystal laser by using Nd：CaGdAI04 （Nd：CGA） as the gain medium. With a pair of SF6 prisms to control the dispersion compensation, laser pulses as short as 850fs at 1079nm are obtained with a repetition rate of 124.6 MHz. The measured threshold pump power is 1.45 W. A maximum average output power of 122mW is obtained under the pump power of 5.9 W. These results show that Nd：CGA could be a promising laser medium for generating femtosecond ultrashort pulse at about 1 μm.
文摘We have developed a Nd:YAP single crystal Aber laser with linearly polarised light output at 1.0795μm.The laser is 100μm in diameter and operated with a threshold of 6.65mW.The slope efficiency is 12.9%.
基金the National Natural Science Foundation of China (50571052)
文摘The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction （XRD）, differential scanning calorimeter （DSC）, and transmission electron microscopy （TEM）.The results indicated that the as-cast Nd60Fe20Al10Ni10-xYx（X=-0, 2） amorphous alloys were fabricated with some quenched-in crystals, which could be restrained by Y. With the effect of yttrium, both the crystallization temperature and exothermic peak shifted to higher temperatures, illustrating that the thermal stability could be improved. The addition of Y changed the crystallization process and final crystallization results. Moreover, the crystallites in the amorphous matrix became more homogeneous and smaller. Meanwhile, Y was useful for the passivation of oxygen in chemistry and restrained the negative effect of oxygen. The activation energies of the start of crystallization and peaking were 1.21 and 1.16 eV, respectively, according to the Kissinger equation.
文摘This paper reports the growth, X-ray diffraction and spectroscopy of Nd3＋：Sr3Gd2（BO3）4 crystal. A Nd3＋：Sr3Gd2（BO3）4 crystal with dimensions of φ20 × 45 mm3 has been grown by the Czochralski method. Nd3＋：Sr3Gd2（BO3）4 crystal belongs to the orthorhombic system, space group Pnma （D2h） with a = 0.7401, b = 1.604 and c = 0.8755 nm. The absorption and emission spectra of Nd3＋：Sr3Gd2（BO3）4 were investigated. The absorption cross section oa is 3.11 × 10^-20cm2 at 808 nm. The absorption transition at 808 nm has an FWHM of 14 nm. The luminescence lifetime τf is 51.7 μs. The emission cross section oc at 1064 nm wavelength is 1.09 × 10^-19 cm2.
文摘The neodymium tungstate single crystals Nd-2(WO4)(3) were grown using the Czochralski method. The energy level scheme of Nd3+, was obtained through the spectral measurement. The upconversion luminescence of the crystals at 457 and 657 nm, corresponding to the (D5/2-->I11/2)-D-4-I-4 and (2)G(7/2)-->I-4(9/2) transitions, respectively, excited by 808 nm of a laser diode, was observed at room temperature. The fluorescence intensity and the excitation light power have a linear relationship at 457 nm and a quadratic relationship at 657 nm.
基金supported by the National Natural Science Foundation of China (No. 50744014)the National Basic Research Foundation (No. 2004CCA04000)+3 种基金Science and Technology Department of Zhejiang Province (Nos. 2008C21046 and 2008C11086-1)the Natural Science Foundation of Zhejiang Province,China (No. Y406389)the Research and Development Program of Ningbo Bureau of Science and Technology (No. 2006B100054)K.C.Wong Magna Found in Ningbo University
文摘Amorphous （Nd,Pr）13Fe80Nb1B6 ribbons were crystallized at 670-730°C for 5-25 min to study the effects of isothermal crystallization on their behavior and magnetic properties. XRD results indicate that the isothermal incubation time is 12, 5, and less than 5 min at 670, 700, and 730°C, respectively. High coercivities, with the maximum value of iHc = 1616 kA/m at 700°C for 19 min, measured by a physical property measurement system, are obtained in the crystallized ribbons. This is mainly attributed to the addition of Pr and Nb, because Pr2Fe14B has a higher anisotropic field than Nd2Fe14B, and Nb enriched in the grain boundary regions can not only reduce the exchange-coupling effects among hard grains, but also impede grain growth during the crystallization process. In addition, it should also be related to the characteristics of the furnace that the authors designed.
文摘The passively Q-switched and mode-locked（QML） characteristics in a diode-pumped Nd∶GdVO4 laser with Cr4+∶YAG saturable absorbers have been demonstrated. A maximum average output power of 710mW has been obtained in the QML laser. The maximum energy of a single Q-switched pulse is 52.5μJ, with the corresponding pulse width of 30ns and the peak power of 1.75kW, at the incident pump power of 7.75W. The repetition rates of the Q-switched envelope and the mode-locked laser pulse are 16.7kHz and 680MHz, respectively.
文摘The title complexes （LnL3 （HL） （H2O） ]2· 2EtOH·2H2O （Ln= Nd （1）, La （2）, HL=adamantanecarboxylic acid） were prepared and determined by single-crystal X-ray diffraction. Both complexes crystallize in triclinic system with space group P 1^-, cell parameters are： complex （1） a = 1.0556（2） nm, b =1.4913（3） nm, c = 1.4920（3） nm, a = 106.26 （3）°, β=93.51（3）°, γ=97.23（3）°, V=2.2253 （5） nm^3, Dcal=1.409 g · cm^-3, Z = I , F （ 000 ） = 990, μ（Mo Kα） = 1. 225 mm^-1, M, = 1884.50; complex （2） a = 1.0453（2） nm, b = 1.4971（3）nm, c = 1.5052（3） nm, α = 106.07（3）°, β =93.58 （3）°, γ=97.56（3）°, V=2.2391（5）nm^3, Dcal= 1.397 g·cm^-3, Z = 1, F（000） =984, μ（Mo Kα） = 1.015 mm^-1, Mr= 1877.88. The final R and wR are 0. 0396 and 0. 1062 for 8589 （1 ≥ 2σ （I）） observed reflections for complex （1）, 0.0505 and 0. 1344 for 8417 （ 1 ≥ 2σ （1） ） observed reflections for complex （2）, respectively. The crystals are consisted of a binuelear molecule. The coordination geometry of the Ln（ Ⅲ ） ion can be described as trieapped trigonal prism.
文摘The reaction of NdCl_3 with lithium methylnaphthalene in 1:2 mole ratio in THF generates black powder. The powder reacts with cyclooctatetraene(COT)in THF to form the title complex.[Li(THF)_4Nd(C_8H_8)_2]· 2THF crystallizes in the monoclinic space group P2/c with unit-cell dimensions a=1.7858(7)nm, h=1.3243(4)nm,c=1.8086(6)nm.β=106.52(4)°,V=4.10 nm^3 and D_c=1.268 g/cm^3 for Z=4. F(000)=1660,R=0.0774,R_n=0.0733.The complex consists of discrete ion-pair and two THF molecules adduct.In the anion,the neodymium atom is coordinated by two COT rings.The structure of the cation shows that the lithium atom is attached with THF molecules only.
文摘The Nd^3＋ 3.2% （atom fraction）：KGd（WO4）2 crystal was grown by Kyropoulos method. The absorption spectrum and fluorescence spectrum of Nd^3 ＋ ： KGW crystal were measured. The absorption cross sections at 808 nm（0. 6799 × 10^-20 cm^2） were calculated, and the output wavelength of fluorescence is 1064 and 1351 nm. The diode-pumped laser was operated both in the free-running and passively Q-switched operating modes. The maximum laser output（1064 nm） is 326 mW with 62.7 % slope efficiency when input energy is 900 mW. The beam quality factor M^2 ≈ 1.1. The green light of 532 nm is obtained in frequency doubling operation. The laser is passively Q-switched by using Cr^4＋ ：LuAG as saturable absorber. The pulse width is 170 ns at repetitive frequency of 15 kHZ.
文摘The neodymium ions doped gadolinium vanadate (Nd∶GdVO_4) single crystals were successfully grown by Czochralski method. Chemical etching technique was used to reveal the dislocation structure of the crystals. An average dislocation density of (100) plane is 600 pits/mm 2. The crystal-morphology can be used to determine crystal orientation accurately with simple optical method.
基金Supported by the National Natural Science Foundation of China (No.60808033)Natural Science Foundation of Jiangxi Province (No.2008GZW0012)
文摘The Nd^3＋：LiGd（WO4） 2 crystal with dimensions of 25mm×28mm×16mm was grown by the top-seeded solution growth method from the 60 mol% Li2W2O7 flux. LiGd（WO4） 2 crystallizes in the tetragonal system with space group I41/a（C4h^6） and cell parameters： a = 5.1986 and c = 11.2652A. The hardness is about 5.0 Mohs＇ scale. The specific heat is 0.40 J·g^-1·K^-1 at 50 oC. The thermal expansion coefficients for a-and c-axes are 1.314×10^-5 and 2.052×10^-5 K^-1,respectively. The room-temperature polarized absorption and emission spectra and the fluorescence decay curve was measured. The parameters of oscillator strengths,the spontaneous transition probabilities,the fluorescence branching ratios,the radiative lifetimes,and the emission cross sections have been investigated based on Judd-Ofelt theory and Füchtbauer-Ladenburg method. The absorption cross-section is 5.19×10^-20 cm^2 at 805 nm for π-polarization and its line width is 15 nm; the emission cross section is 1.726×10^-19 cm^2 at 1060.5 nm for π-polarization. The fluorescence and radiative lifetimes are 86 and 158 μs,respectively. The fluorescence quantum efficiency is 54.43%.
基金Project supported by the National Basic Research Program of China (Grant No 2006CB601101)
文摘X-ray powder diffraction, resistivity and magnetization studies have been performed on polycrystalline Nd（FexMn1-x）2Si2 （0≤x 〈 1） compounds which crystallize in a ThCr2Si2-type structure with the space group 14/mmm. The field-cooled temperature dependence of the magnetization curves shows that, at low temperatures, NdFe2Si2 is antiferromagnetic, while the other compounds show ferromagnetic behaviour. The substitution of Fe for Mn leads to a decrease in lattice parameters a, c and unit-cell volume V. The Curie temperature of the compounds first increases, reaches a maximum around x=0.7, then decreases with Fe content. However, the saturation magnetization decreases monotonically with increasing Fe content. This Fe concentration dependent magnetization of Nd（FexMn1-x）2Si2 compounds can be well explained by taking into account the complex effect on magnetic properties due to the substitution of Mn by Fe. The temperature＇s square dependence on electrical resistivity indicates that the curve of Nd（Fe0.6Mn0.4）2Si2 has a quasi-linear character above its Curie temperature, which is typical of simple metals.
