Nd3+:Y0.5Gd0.5VO4晶体生长和基本特性

Nd^3 :Y0.5Gd0.5VO4晶体作为一种新的激光材料，可以用中频感应加热提拉法生长。X射线粉末衍射分析表明它的结构与Nd^3 :YVO4晶体结构相同，它的晶格常数介于YVO4和NdVO4晶格常数之间。用ICP光谱法测定晶体中Nd^3 含量为0．8at％，分凝系数为0．8，与Nd^3 :GdVO4晶体中Nd^3 的分凝系数0．78相当；用称重法测定其密度为5．00g／cm^3；用稳态纵向热流法测出其室温热导率为12．5W／mK。实验表明Nd^3 :Y0.5Gd0.5VO4晶体有希望作为高功率ID泵浦激光晶体材料。     

Semianalytical thermal analysis on a Nd:YVO(4) crystal

Based on analytical theory of anisotropy, distributions of thermal distortion and temperature field within a diode-end-pumped rectangular Nd:YVO(4) laser crystal are investigated. A thermal model that matches the actual working state of the laser crystal is established by analyzing the working characteristics of the Nd:YVO(4) laser crystal. A novel method, to the best of our knowledge, is adopted to solve the heat conduction equation of the anisotropic medium. General solutions of the temperature field, thermal strain field, and thermal distortion field of the Nd:YVO(4) crystal are obtained. The effect of anisotropic thermal parameters on the thermal strain field of the Nd:YVO(4) laser crystal is also analyzed quantitatively. Research results show that a maximum temperature rise of 244.9 degrees C and a maximum thermal distortion of 1.99 mum can be obtained in the center of the pump face when the Nd:YVO(4) laser crystal doped with 0.5 at. % Nd(3+) is diode end pumped in the center of the front end face with 15 W output power. This method can be applied to other thermal analyses of laser crystals and offers a theoretical basis to solve thermal problems effectively in the laser system.     

Measurement of refractive indices and thermal refractive-index coefficients of 7.5-mol.% Nb:KTiOPO4 crystal

The principal refractive indices and the thermal refractive-index coefficients of 7.5-mol.% Nb:KTiOPO(4) crystal were measured by autocollimation for wavelengths of 0.53975, 0.6328, 1.0795, and 1.3414 microm from room temperature to 143 degrees C. The Sellmeier equations at room temperature were obtained and used to calculate the optimal phase-matched angles for 1.0642 and 1.0795 microm. The calculated and experimental values are in good agreement.     

Yb0.03Y0.19Gd0.78VO4晶体的生长和性能

液相合成了Yb∶YGdVO4多晶料,采用中频感应加热Czochralski法生长了Yb0.03Y0.19Gd0.78VO4晶体.用浮力法测定其密度为5.29g/cm3,X射线粉末衍射分析表明它的结构与YVO4和GdVO4的晶体结构相同,并计算出了它的晶胞参数为a0=b0=0.7191nm,c0=0.6329nm.用激光脉冲法测量了晶体的热扩散系数,比较了晶体a轴和c轴的热扩散系数随温度的变化关系.实验表明Yb0.03Y0.19Gd0.78VO4晶体有希望适合作为LD泵浦的激光晶体材料.     

Complex refractive-index spectrum of liquid crystal in the infrared

The ordinary and extraordinary complex refractive indices, n(o) - j kappa(o) and n(e) - j kappa(e), of a nematic liquid crystal were measured in the infrared region at 3.0-11.5-microm wavelength. The complex refractive indices were evaluated in terms of the angular dependence of the reflectance. Semicylindrical CsI prisms and a goniometer were used for measurement of the reflectance in a wide incident-angle range and throughout the wide infrared spectral region. Refractive indices n(o) and n(e) changed notably near the absorption wavelength. Negative birefringence, i.e., n(e) < n(o), was observed in the vicinity of 6.6 microm, where n(e) changed more than did n(o).     

Thermal diffusivity, specific heat, thermal conductivity, coefficient of thermal expansion, and refractive-index change with temperature in AgGaSe2

Measurement of the key thermo-optic properties of AgGaSe2 in the temperature range below 300 K is reported. Values of these properties on cooling become favorable for the higher average-power operation of nonlinear optical frequency converters using this material.     

Passively mode-locking Nd:Gd0.5Y0.5VO4 laser with an In0.25Ga0.75As absorber grown at low temperature

We have demonstrated stable self-starting passive mode locking in a diode-end-pumped Nd:Gd0.5Y0.5VO4 laser by using an In0.25Ga0.75As absorber grown at low temperature (LT In0.25Ga0.75As absorber). An In0.25Ga0.75As single-quantum-well absorber, which was grown directly on the GaAs buffer by use of the metal-organic chemical-vapor deposition technique, acts simultaneously as a passive mode-locking device and as an output coupler. Continuous-wave mode-locked pulses were obtained at 1063.5 nm. We achieved a pulse duration of 2.6 ps and an average output power of 2.15 W at a repetition rate of 96.4 MHz.     

The dielectric constants of CaWO4, Nd/CaWO4 and Gd/CaWO4

The dielectric constants and loss for pure single crystals of calcium tungstate and for neodymium- and gadolinium-doped crystals have been measured from 1 to 40 MHz. At 20? C the values for pure calcium tungstate areε _a′ = 11.3±0.4,ε _c′ = 9.1±0.4, at 1 MHz. These agree closely with Brower and Fang's data and increase very slightly with frequency. Doping at levels of less than 1.0 at.% produced no measurable change inε _a′ orε _c′. The dielectric loss, tanδ, which was isotropic, was about 5×10^?3 for all specimens at 1 MHz; at higher frequencies, tan? increased and, in the neodymium-doped crystals, the high frequency loss was found to be concentration dependent.     

Gd2O2SO4粉体的合成及其晶体结构确定

通过750℃,2h煅烧Gd2O3和H2SO4(摩尔比1:1)的前驱体方法合成了Gd2O2SO4粉体.利用Gd2O2SO4的X射线粉末衍射数据和Material Studio 4.0 Reflex模块中Powder solve技术和Rietveld精修方法对Gd2O2SO4的晶体结构进行了研究.研究表明:Gd2O2SO4具有空间群为PMNB(62)的正交晶系,晶胞参数为a=1.2996nm,b=0.8117nm,c=0.4184nm,V=0.440698nm3,Z=4,计算密度为6.6949g/cm3,并确定了晶胞中原子的位置,Rietveld精修得到的Rwp=9.15%.     

Review and assessment of measured values of the nonlinear refractive-index coefficient of fused silica

The literature describes more than 30 measurements, at wavelengths between 249 and 1550 nm, of the absolute value of the nonlinear refractive-index coefficient of fused silica. Results of these experiments were assessed and best currently available values were selected for the wavelengths of 351, 527, and 1053 nm. The best values are (3.6 ? 0.64) x 10(-16) cm(2)/W at 351 nm, (3.0 ? 0.35) x 10(-16) cm(2)/W at 527 nm, and (2.74 ? 0.17) x 10(-16) cm(2)/W at 1053 nm.     

Changes of the local magnetic properties of the optically excited Nd3+ ions and their manifestation in the near IR spectra of the Nd0.5Gd0.5Fe3(BO3)4 crystal

Polarized absorption spectra of f–f transitions ⁴I_9/2 → ⁴F_3/2 and (²H_9/2 + ⁴F_5/2) in the Nd³⁺ ion in the Nd_0.5Gd_0.5Fe₃(BO₃)₄ single crystal were studied as a function of temperature in the range of 2–40 K and as a function of magnetic field in the range of 0–65 kOe at 2 K. It was found out that the selection rules for f–f electron transitions substantially changed in the magnetically ordered state of the crystal, and they strongly depended on the orientation of the Fe and Nd ions magnetic moments relative to the light polarization. The splitting of the ground and excited states of the Nd³⁺ ion in the exchange field of the Fe sublattice were determined. It was revealed that the value of the exchange splitting (the exchange interaction) in the excited states did not correlate with the theoretical Landé factors. The Landé factors of the excited states were experimentally found. In general, the local magnetic properties in the vicinity of the excited ion depend substantially on its electron state. In particular: (1) in one of the excited states a weak ferromagnetic moment appears, (2) the changes of type of the local magnetic anisotropy take place in some excited states, and (3) in some excited states the energetically favorable orientation of the Nd³⁺ ion magnetic moment is opposite to that in the ground state. In some excited states the nonequivalent Nd³⁺ centers were found out.     

Polarization effects in a KGd(WO4)2:Nd crystal

Data are presented that demonstrate that, when a laser beam polarized at 45° to the vertical (horizontal) is passed through plane-parallel plates cut from a Nd-doped (4%) potassium gadolinium tungstate crystal and placed between crossed polarizers, the intensity and polarization of the transmitted light are periodic functions of the angle of incidence of the light. When scanned in two mutually perpendicular directions, the plates exhibit highly anisotropic transmission. The polarization at the intensity minima and maxima at the analyzer output is not orthogonal, in contrast to uniaxial crystals.     

Modeling of frequency doubling and tripling with measured crystal spatial refractive-index nonuniformities

Efficient frequency doubling and tripling are critical to the successful operation of inertial confinement fusion laser systems such as the National Ignition Facility currently being constructed at the Lawrence Livermore National Laboratory and the Omega laser at the Laboratory for Laser Energetics. High-frequency conversion efficiency is strongly dependent on attainment of the phase-matching condition. In an ideal converter crystal, one can obtain the phase-matching condition throughout by angle tuning or temperature tuning of the crystal as a whole. In real crystals, imperfections in the crystal structure prohibit the attainment of phase matching at all locations in the crystal. We have modeled frequency doubling and tripling with a quantitative measure of this departure from phase matching in real crystals. This measure is obtained from interferometry of KDP and KD*P crystals at two orthogonal light polarizations.     

Paraxial wave equation for the extraordinary-mode beam in a uniaxial crystal

With reference to the analysis contained in J. Opt. Soc. Am. 73, 920 (1983), certain comments on and clarifications of the paraxial wave equation pertaining to the extraordinary-mode beam propagating obliquely to the optic axis in a uniform uniaxial crystal are presented.     

Studying the coefficient of thermal conductivity for liquid metals

We discuss a method for an experimental study of the coefficient of thermal conductivity, specific heat capacity, and the specific electrical resistance of metals in the solid and liquid states, as well as the data that we have obtained with respect to the indicated properties of Bi, In, Cd, and Pb.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 57, No. 6, pp. 892–896, December, 1989.     

Spectra and broad-spectral laser operation of a disordered Nd:LiLa(MoO4)2 crystal

The crystal characteristics of a disordered Nd:LiLa(MoO₄)₂ laser crystal were investigated in detail, including its structure, absorption, emission and Raman scattering spectra. Laser operation, end-pumped by an 808?nm diode laser, has been demonstrated in both a concave-plano and plane-parallel resonator cavity. A broad-spectral dual-peak laser emission at 1061?nm and 1060?nm with a full width at half maximum of 2?nm was obtained in the experiment. A maximum output power of 267?mW was obtained in the concave-plano cavity. However, in the plane-parallel cavity, laser output of 381?mW was obtained, giving a slope efficiency of 14.5%. The results lay the groundwork for Raman, mode-locked and tunable laser applications generated by a Nd:LiLa(MoO₄)₂ laser crystal.     

Experimentally determined r13 electro-optic coefficient for a lithium niobate crystal

Experimental determination of the electro-optic coefficient r13 of a lithium niobate crystal is described. The crystal in this experiment is z cut, used as a substrate for a Fabry-Perot etalon. I computed the r13 coefficient from the measured voltage tuning curve of the Fabry-Perot etalon. It is find that the measured value of r13 is lower than most of the reported values in literature.