Investigations on the Growth and Laser Properties of Nd:GdVO4 Single Crystal

In this paper, we report the growth of laser crystal Nd:GdVO₄ by the Czochralski method, and discuss the morphology of the crystal. The polarization absorption and emission spectra of Nd:GdVO₄ were measured. The lifetime of the Nd:GdVO₄ at 1064 nm is 100μs. An output power up to 1 W at 1064 nm has been achieved with a 3 mm × 3 mm × 1 mm crystal sample when pumped by a 1.9 W cw laser diode.     

Thermal conductivity and refractive indices of Nd:GdVO4 crystals

The thermal conductivities of Nd:YAG, M(Y,Gd)VO₄ crystals were measured at 298 K. The value of Nd:GdVO₄ crystal along <001> direction was 11.4 W/mK, which was higher than that of YAG crystal measured to be 10.7 W/mK. The principal refractive indices of Nd:GdVO₄ crystal in the temperature range from 20 °C to 170 °C were determined by auto‐collimation method. Based on the measured values of refractive indices, the Sellmeier equation and expression of temperature dependence of refractive indices have been obtained. The measured results show that the birefringence Δn is 0.22007 at 20 °C and temperature coefficient of birefringence is 4.33 × 10⁻⁶/°C for 1.064 μm. These results prove that the GdVO₄ crystal is a laser crystal with excellent thermal and birefringence properties. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of Nd:CLNGG crystal

The disordered laser crystal neodymium-doped calcium lithium niobium gallium garnet (Nd:CLNGG) was successfully grown by the Czochralski method. Its thermal properties, including the average linear thermal expansion coefficient, thermal diffusion coefficient, specific heat, and thermal conductivity were measured, and continuous-wave (CW) laser performance at 1.06 μm was demonstrated. The maximum power of 1.48 W was achieved with corresponding optical conversion efficiency of 12.4% and slope efficiency of 16.2%.     

Growth and properties of Nd:Lu3Ga5O12 laser crystal by floating-zone method

Neodymium (Nd) doped lutetium gallium garnet (Nd:Lu₃Ga₅O₁₂, Nd:LuGG) single crystal was successfully grown by the optical floating-zone method for the first time to our knowledge. Its absorption and luminescence spectra at room temperature were measured. By using the J–O theory, the spectral parameters of Nd:LuGG were calculated, which indicated that Nd:LuGG should possess comparable and even better laser properties than Nd:YAG. The maximum output power of 855 mW at 1062 nm was achieved with slope efficiency of 23.4% under a pump power of 5.2 W, and optical conversion efficiency of 16.4%. All the results show that Nd:LuGG is a potential laser material.     

Pb4.7Ba0.3Ge3O11 Crystals as New Acoustically Induced Nonlinear Optical Materials

A coustically induced optical second harmonic generation (SHG) and two‐photon absorption (TPA) in ferroelectric Pb_4.7Ba_0.3Ge₃O₁₁ crystals have been found. We have found that with increasing acoustical power, the SHG for YAG:Nd laser light (λ=1.06 μm) increases and achieves its maximum value at acoustical power density about 1.75 W/cm². The evaluated SHG values were 23 % less comparing with χ₂₂₂ tensor of the KDP single crystals. With decreasing temperature, the acoustically induced SHG signals trongly increases below 29 K. The maximal acoustically induced SHG has been observed at acoustical frequencies lying with in the ranges 12‐17 kHz, 22‐23 kHz and above 26 kHz. This behavior reflects nonlinear superposition of the nonlinear optical susceptibilities stimulated by externallyinduced electron‐phonon anharm onicity. We have observed substantial increase of the TPA (for the acoustical power W=1.8 W/cm²) at high hydrostatic pressures (about 16 GPa) and low temperatures (below 16 K). This one confirms complicated influence of the electron‐phonon interactions in the ferroelectricson the observed nonline aroptical dependences.     

Optical and laser properties of Nd:LuVO4 crystal

Polarized absorption spectra of Nd:LuVO₄ crystal were measured at room temperature. The optical parameters of π polarization and σ polarization were calculated by Judd‐Ofelt theory. Meanwhile, the phenomenological intensity parameters: Ω₂, Ω₄, and Ω₆ were obtained, then the parameters were used to calculate the luminescence parameters of Nd:LuVO₄ crystal, including oscillator strengths, fluorescence branching ratio, radiative lifetime and integrated emission cross‐sections. Experiments of a‐cut and c‐cut Nd:LuVO₄ lasers were also performed, and opt‐opt conversion efficiency and slope efficiency were 40.3%, 50.5% for a‐cut and 23.6%, 30.9% for c‐cut, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nd^3＋：KGd（WO4）2激光晶体的研究

合成了一系列不同Nd     

Thermal and Laser Properties of Nd:YVO4 Crystal

Nd:YVO₄ crystal has been grown by Czochralski method. The data of thermal expansion and specific heat have been measured. The thermal expansion coefficients along a- and c-axis are a₁ = 2.2 x 10^-6 /K, and a₃ = 8.4 x 10^-6 /K respectively. The specific heat is 24.6 cal/mol x K at 330 K. The large anisotropy along c- and a-axis of thermal expansion coefficients is explained by the structure of YVO₄ crystal. 921 mW output laser at 1.06 mikrom has been obtained with a 3 mm x 3 mm x 1mm crystal sample when pumped by 1840 mW cw laser diode, and the slope efficiency is 55.5%.     

Cr,Nd:GSAG晶体生长、光谱及LD泵浦激光性能研究

Cr,Nd:GSAG是一种性能优良的激光晶体,但是关于它的LD泵浦激光性能的研究很少.用提拉法生长了Cr,Nd:GSAG晶体,测定了它的化学成分、结构,初步测试了它的激光性能.晶体的(111)面X射线摇摆曲线半高全宽为0.055°.采用Rietveld方法精修X射线粉末衍射谱得到了Cr,Nd:GSAG晶体的原子结构参数、温度因子等.Cr,Nd:GSAG的最强吸收峰位于808.6nm处,吸收截面为3.38×10-20cm2.808nm光激发下,Cr,Nd:GSAG的最强发射峰位于1060nm,发射截面为6.04×10-20cm2,并测得激光上能级4F3/2的荧光寿命为274μs.利用808nm连续波LD泵浦实现了1060nm的激光输出,在输入功率为8.88W时,最大输出功率为0.513W,斜效率为6.73;,光-光转换效率为5.78;.此外还讨论了Cr,Nd:GSAG晶体中的Cr3+与Nd3+之间的能量传递机理.     

Nd:YVO4键合晶体声光调Q输出泵浦的光参量振荡器

通过采用非线性相位匹配的KTiOPO4晶体,成功实现了使用LD泵浦的Nd∶YVO4/Nd∶YVO4/Nd∶YVO4键合晶体激光器声光调Q输出泵浦的光参量振荡.当泵浦功率为8.29 W,声光调制频率为30 kHz时,获得了0.92 W的1570 nm信号光的最大平均输出功率,信号光的最窄脉宽为1.04 ns,最大峰值功率为29.5 kW.光光转换效率:对1064 nm泵浦光为54.4;,而对808 nm二极管泵浦光束只有11.1;.     

Growth and Optical Properties of Tm:GdVO4 Single Crystal

Thulium-doped gadolinium vanadate (Tm:GdVO₄) single crystal has been successfully grown by a modified Czochralski (CZ) technique. Effective distribution coefficient of Tm was determined to be 0.74. Absorption characterization was performed in the 800 nm region and the maximum absorption peak was found at 799 nm for p polarization. Fluorescence spectra for tuning at the maximum absorption were obtained around 1.8-2.0µm region with 100 nm bandwidth. This suggests that a Tm:GdVO₄ crystal is expected as a new promising LD pumped solid-state laser in the 2µm region.     

Crystal growth,quality characterization and THz properties of DAST crystals

4‐N, N‐diethylamino‐4’‐N’‐methyl‐stilbazolium tosylate (DAST) crystals were grown by slope nucleation method (SNM). The crystal structure of grown DAST crystals was characterized by single crystal X‐ray diffraction with demonstrating X‐ray diffraction main peaks. The crystal defects were analyzed by the synchrotron radiation X‐ray topography. It was found that the unbalanced temperature gradient, the Teflon groove and the super saturation fluctuation were primary causes of crystal defects. Furthermore, widely tunable THz waves ranging from 1.16 to 16.71 THz were generated from 1 mm‐thick DAST crystal using the optical parametric oscillator (OPO). It was obtained that the THz output energy was 27.4 nJ (peak power of 2.74 W) and the highest conversion efficiency was 1.37 × 10⁻⁵ at 3.8 THz.     

Laser‐induced crystal growth of nonlinear optical Ba3Ti3O6(BO3)2 on glass surface

Nonlinear optical Ba₃Ti₃O₆(BO₃)₂ crystals were patterned on the surface of CuO (1 mol%)‐doped 40BaO‐40TiO₂‐20B₂O₃ glass by irradiations of continuous‐wave Nd:YAG (wavelength: λ=1064 nm) and Yb:YVO₄ (λ=1080 nm) lasers. Laser energies absorbed by Cu²⁺ ions were transferred to the lattice system through a nonradiative relaxation process, consequently heating the glass and inducing local crystallizations. For the lines patterned by Yb:YVO₄ laser irradiations with a power of 1 W and a scanning speed of 20 μm/s, a c‐axis orientation of Ba₃Ti₃O₆(BO₃)₂ crystals along the laser scanning direction is proposed from measurements of X‐ray diffraction analyses, polarized optical photographs, polarized micro‐Raman scattering spectra, and azimuthal dependence of second harmonic generations. The laser‐induced crystallization technique is found to be applied successfully for the spatially selective patterning of nonlinear optical Ba₃Ti₃O₆(BO₃)₂ crystals in glass. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nd3+:LiLa(MoO4)2晶体生长、光谱和激光特性

本论文报道了Nd3+:LiLa(MoO4)2晶体生长、光谱和激光特性.采用提拉法生长出尺寸为φ20×34mm3的Nd+3+:LiLa(MoO4)2晶体.应用Judd-Ofelt理论计算了Nd3+离子在Nd3+:LiLa(MoO4)2晶体中唯象强度、自发发射跃迁几率、荧光分支比、辐射跃迁寿命和荧光量子效率.Nd3+:LiLa(MoO4)2晶体的偏振吸收跃迁截面分别为9.52×10-20cm2(π-偏振)和4.46×10-20cm2(σ-偏振).它的偏振发射跃迁截面分别为0.67×10-19cm2(σ-偏振)和1.02×10-19cm2(σ-偏振).在氙灯泵浦下,获得74.4mJ的1.06μm的激光输出,激光阈值为0.676J,激光总效率和斜率效率分别为0.39;和0.48;.     

Growth and properties of an organometallic nonlinear optical crystal: bis(isothiocyanato)‐bis(4‐methylpyridine)zinc(II) (Zn(SCN)2(C6H7N)2)

Bis(isothiocyanato)‐bis(4‐methylpyridine)zinc(II)(Zn(SCN)₂(C₆H₇N)₂), (abbreviated as ZBNC) single crystals of optical quality have been grown from acetone solution by the slow temperature‐lowering method. Its solubilities at different temperatures in acetone were measured. The X‐ray powder diffraction (XRPD) spectroscopy of ZBNC crystal was performed at room temperature. The second harmonic generation (SHG) efficiency was determined by powder technique of Kurtz and Perry using Nd:YAG laser, which is equivalent to KDP crystal. The thermal decomposition process was characterized by thermal gravity and differential thermal analysis (TG\DTA). The specific heat of the crystal is 1440.67 J/mol·K at 325 K. The IR spectrum was recorded in the 500∼3500 cm^–1 region, using KBr pellets on a Nicolet 170sx FT‐IR spectrometer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation of High-quality InGaAsP/InP Heterostructures for Edge-emitting 1.3 μm LED's

Effects of varying the composite heterostructure geometry have been investigated in the context of InGaAsP/InP (λ λ= 1.3 μm) non-coherent radiation sources. The study has been guided by a preliminary theoretical analysis and complemented by evaluation of the statistics in sample ensembles. Optimum construction diodes emit 600–700 μW/facet of optical power. The added quaternary layer of intermediate bandgap (Λ_g λ= 1.1 μm) has been found to have benefical effect on the quantum efficiency and reproducibility of the manufacturing process.     

Edge-Defined Film-Fed (EFG) Growth of Rare-Earth Orthovanadates REVO4 (RE=Y,Gd): Approaches to Attain High-Quality Shaped Growth

In spite of their superior laser and polarizer properties rare-earth orthovanadates (REVO₄) single crystals have not been adopted yet into extensive industrial applications because of crystal growth difficulties. The main problems of CZ technique are compositional change and diameter instability. This work presents the first attempt to apply the edge-defined film-fed growth (EFG) technique by which well-shaped REVO₄crystals have been grown directly. The capillary properties of YVO₄ and GdVO₄ melt have been measured. The applicability of shaped growth for rare-earth orthovanadate family was approved by successful EFG growth of transparent rod-like macro-defect-free single crystals of YVO₄ and GdVO₄. We address two main approaches to enhance the quality of EFG crystals: (i) meniscus and crystal shape stability dependence on die top shape and (ii) the strategy of effective operating control. Concave die top was found to be the best choice for high-quality EFG growth of REVO₄ along [001] direction. The spectral analysis of weight signal from growing crystal was shown to be a useful feedforward clue to prevent crystallinity degradation at a very early stage. A reasonable stability of the EFG process was achieved using [211], [101], [001] and [100] pulling directions.     

YAl3(BO3)4: Crystal growth and characterization

The growth and characterization of YAl₃(BO₃)₄ (YAB), a potential nonlinear optical crystal for the fourth harmonic generation of Nd:YAG laser, was reported. Using top-seeded solution growth method, a YAB crystal with the dimensions of 16×16×18 mm³ was obtained from B₂O₃–Li₂O flux system. The advantages of this flux system and the growth process were discussed in detail. The as-grown YAB crystal was verified by powder X-ray diffraction. The transparency spectra indicated that the cut-off edge of the as-grown YAB was 170 nm. The fourth harmonic generation of a frequency doubled Nd:YAG laser, from 532 to 266 nm, was carried out with a YAB crystal doubler for the first time. Output pulse power obtained was 2.4 mW at 266 nm and the conversion efficiency from 532 to 266 nm was about 15.6%.     

Vertical Bridgman growth and characterization of large ZnGeP2 single crystals

The growth of ZnGeP₂ crystals by seeded Vertical Bridgman method was studied. High-quality near-stoichiometric ZnGeP₂ single crystals obtained were of 20–30 mm in diameter and 90–120 mm in length. By selection of the seed crystallographic orientation the single crystal ingots without cracks and twins were grown, as shown by X-ray diffraction. The infrared transmission property of the ZnGeP₂ crystals was studied by the calculated optical absorption coefficient spectra. The results showed that after thermal annealing of the crystals the optical absorption coefficient was ～0.10 cm^?1 at 2.05 μm, and ～0.01 cm^?1 at 3–8 μm. The rocking curves patterns of the (4 0 0) reflection demonstrated that the as-grown single crystals possessed a good structural quality. The composition of the crystals was close to the ideal stoichiometry ratio of 1:1:2. The low-loss typical ZnGeP₂ samples of 6 mm×6 mm×15 mm in sizes were cut from the annealed ingots for optical parametric oscillation experiments. The output power of 3.2 W was obtained at 3–5 μm when the incident pumping power of 2.05 μm laser was 9.4 W, and the corresponding slope efficiency and the conversion efficiency were 44% and 34%, respectively.     

Continuous-wave laser operation of disordered double tungstate and molybdate crystals doped with ytterbium

Several ytterbium doped disordered doubles tungstate and molybdate crystals, NaGd(WO₄)₂, NaLa(WO₄)₂, NaLa(MoO₄)₂ and LiGd(MoO₄)₂, were grown with sufficient Yb-doping and optical quality. The crystal field splitting of the Yb³⁺ multiplets and the lifetimes are similar to the biaxial monoclinic double tungstates but the peak absorption cross sections are roughly one order of magnitude lower. Room temperature cw laser operation was achieved under Ti:sapphire and diode laser pumping. The polarization dependence of the laser emission and possible power scaling were studied. The slope efficiency achieved with the best sample, Yb:LiGd(MoO₄)₂, was 64.5%. The maximum output power obtained was 900 mW for Yb:NaLa(MoO₄)₂ pumped in the absorption maximum. The laser tunability was studied with an intracavity Lyot filter and the tuning ranges (FWHM up to 33 nm) achieved indicate interesting potential for mode-locked femtosecond operation.