Nd:YbVO_4晶体的拉曼光谱和荧光光谱研究

用群论的方法计算了Nd:YbVO4晶体的拉曼活性振动模数目,在室温下测得了其极化拉曼谱线,并指认了在不同几何配置下,各振动模式所对应的频率。同时,测得了室温下晶体的吸收谱,得到了中心波长为808nm吸收峰的半高宽为12nm,并在J-O理论的基础上计算了晶体的光学参数,其三个晶场参数分别为Ω2=6.88945×10-20cm2、Ω4=4.13394×10-20cm2、Ω6=4.54503×10-20cm2,并由此得到4F3/2能级的荧光寿命为178.69μs,1062nm处的荧光分支比为48.85%,积分发射截面为2.786710-18cm2。分别在808nm、940nm激发下测得晶体室温发射谱,观察到了Nd→Yb以及Nd←Yb间的能量传递现象。

Nd:YbVO_4激光晶体的生长及热学性质

用提拉法沿α轴和c轴成功生长出质量优良的Nd：YbVO4新型单晶。采用HRXRD-D5005型高分辨X射线衍射仪测得晶体的摇摆曲线，可以测得（400）面的半峰宽为70．92＂，（004）面的半峰宽为19．80＂。测得掺杂浓度为1％原子分数Nd：YbVO4晶体中Nd离子的有效分凝系数Keff为0．54。在298．15-573．15K温度范围内测量了晶体的热膨胀系数，αa=2．6×10^-6／K，αb=2．5×10^-6／K，αc=8．7×10^-6／K；测得比热值为0．45～0．65J／g·K。测量了晶体的热扩散系数α，从而得到了其热导率λ。

Nd∶CaYAlO_(4)单晶光纤的生长及光谱性能研究

采用微下拉法生长了不同掺杂浓度(0.25%,0.50%,0.75%,1.00%,原子数分数)的Nd∶CaYAlO_(4)单晶光纤。通过X射线衍射测试了单晶光纤晶体结构,结果表明晶体结构为四方晶系。测试了Nd∶CaYAlO_(4)单晶光纤的室温偏振吸收和荧光光谱,测试样品在807 nm附近有很强的吸收。其中,1.00%Nd∶CaYAlO_(4)的吸收最强,在σ偏振方向的吸收系数为4.20 cm^(-1),π偏振方向的吸收系数为4.06 cm^(-1)。1.00%Nd∶CaYAlO_(4)单晶光纤最强发射峰在σ和π偏振下都位于1080 nm,σ偏振方向的发射带宽为17.7 nm,π偏振方向的发射带宽为17.8 nm。0.25%、0.50%、0.75%、1.00%掺杂浓度的Nd∶CaYAlO_(4)单晶光纤4 F 3/2能级的荧光寿命分别为129、133、135和140μs,未观察到浓度猝灭。结果表明Nd∶CaYAlO_(4)单晶光纤是有潜力的超快激光增益介质。

A 200 kHz Q-Switched Adhesive-Free Bond Composite Nd:YVO4 Laser using a Double-Crystal RTP Electro-optic Modulator

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.

Spectroscopic investigation of a new crystal： Nd^3＋,Yb^3＋：YVO4

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%.

Q-switched and Mode-locked Characteristics of Cr^(4+)∶YAG Crystal

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.

Growth and Spectroscopic Properties of Nd^(3+):Sr_3Gd_2(BO_3)_4 Crystal

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.

Thermal Lensing Measurement and Laser Performance of End-Pumped Lightly Doped Nd:GdVO_(4) Crystal

The thermal lensing effect generated in an end-pumped lightly doped Nd:GdVO4 crystal was found to be considerably weaker than that in Nd:YVO4 having the same Nd3+ concentration. Consequently, the laser performance of Nd:GdVO4 at high pump powers over 20 W was found to be superior to that of Nd:YVO4. TEM00 mode cw radiation of 14.3 W at 1.06μm was achieved with an optical conversion efficiency of 55%, and average slope efficiency of 62%.

Growth,Dislocation and Morphology of Nd∶GdVO_4 Single Crystal

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.

Crystal Growth and Properties of Nd:NaBi(WO_4)_2

Nd:NaBi(WO_4)_2 crystals (Nd:NBW) were grown by Czochralski method. The pulling rate is 0.3 mm·h (-1),and the rotational speed of Nd:NBW crystal is 2 r·min (-1). The components of this single crystal were determined by X-ray diffractions,and its corresponding properties were described from thermal gravity and differential thermal analysis experiments. The absorption cross-sections were calculated. The emission band of Nd:NBW crystal was obtained from its luminous spectrum.

Growth and characterization of Nd:Sr_(0.95)Ba_(0.05)WO_4 single crystal

Synthesis of polycrystalline Nd：Sr0.95Ba0.05WO4 by means of liquid-and solid-phase reaction was reported.X-ray powder diffraction results showed that the as-grown Sr0.95Ba0.05WO4 and Nd：Sr0.95Ba0.05WO4 single crystals belonged to tetragonal system and I41/a space group.Transparent Nd：Sr0.95Ba0.05WO4 single crystal could be obtained along c-axis by Czochralski method from the synthesized polycrys-talline material.As the transmittance of Sr0.95Ba.005WO4 single crystal could reach 80%, Nd3＋ ion was adopted to be doped into the single crystal.Spontaneous Raman spectrums of polycrystalline material and single crystal were measured by RERKZN-ELMER2000 and JY-HR800.By using X-ray fluorescence method, the effective segregation coefficients of Nd, Ba, Sr, and W elements in Sr0.95Ba.005WO4 single crystal were estimated as 0.844（0.745）, 0.44, 1.09, and 0.95, respectively.The segregation coefficients of Nd in Sr0.95Ba0.05WO4 were higher than that in BaWO4, and this is as better as a Raman laser crystal.

CRYSTAL STRUCTURE OF DI(α-HYDROXYISOBUTYRATE)DIAQUO NEODYMIUM NITRATE Nd(C_4H_7O_3)_2NO_32H_2O

The crystal structure of di-hydroxyisobutyrate)diaquo neodymium nitrate Nd(C_4H_7O_3)_2NO_32H_2O was determined by X-ray diffraction analysis. It belongs to monoclinic,space group C2/C,with cell dimensionsa=8.996(1), b=8.601(1),c=21.111(3),β=92.38°,V=1632.O,Z=4,D_c=1.83g/cm^3.Crystal structure has been refined by full-matrix least-square techniques giving a final R value of 0.036.The neodymium atom is coordinated to eight oxygen atoms.The nitrate group in complex is not bonded to neodymium,each two neodymium atoms are linked by bridging carboxyl group forming a chain polymeric molecule.

Growth and Characteristics of Nd^(3+):GdAl_3(BO_3)_4 Crystal

Nd3+:GdAl3(BO3)4 (NGAB) crystal with the size of 30 mm was grown from the solvent system of K2O-Gd2O3-MoO3-B2O3 by combining accelerated seed rotation technology with medium seeded solution growth (MSSG) method, and its crystal structure has been determined by X-ray powder diffraction. It crystallizes in the trigonal system, space group R32 with a = 9.2734(2), c = 7.2438(1) ? V = 538 ?, Z = 3 and Dc = 4.379 g/cm3. The absorption and emission spectra of NGAB in the function of s and polarizations at room temperature have been measured. UV generation tuneable in 378～382 nm, green (531 nm) generation and blue generation tuneable in 436～443 nm as well as red (669 nm) generation by self-frequency changing were obtained with the output of 105, 119.5, 445 and 19 mJ/pulse, respectively, when the crystal was pumped by a dye laser.

Spectral Parameters of Nd^(3+) Ion in Nd^(3+):KLu(WO_4)_2 Crystal

The spectral parameters of Nd3+ ions in Nd3+:Klu(WO4)2 crystal were calculated based on Judd-Ofelt theory and obtained as follows: for the oscillator strengths ?λ: ?2 = 7.5029×10-20 cm2, ?4 = 7.1837×10-20 cm2 and ?6 = 3.1189×10-20 cm2; the radiative lifetime is 123 μs; the quantum efficiency is equal to 64.55%; and β1 = 0.5498, β2 = 0.3943, β3 = 0.0551 and β4 = 0.0027 for the fluorescence branch ratios.

Diode Pumped High Peak Power Quasi Q-Switched and Passively Q-Switched Nd:YVO₄Lasers at 1064 nm and 532 nm using Cr:YAG and KTP crystals

Diode end-pumped solid-state lasers have the potential to yield high quality laser beams with high efficiency for laser range finding and warning receiver applications as well as day and night military laser designation systems. In this paper we presents theoretical calculations using Advanced Dynamics Professional LASCAD software and experimental studies for a high power pigtailed fiber diode laser module of 8 W operating at 808 nm with a specially designed high efficiency cooling system, end pumped high-efficiency Nd:YVO4 laser of 3 × 3 × 10 mm rod and overall cavity length of 44 mm. To the best of our knowledge a self Q-switching effects was generated in Nd:YVO4 laser by changing the cavity dimensions and the position of the intracavity KTP crystal at certain regime of operation for the first time, in which the cavity length is reduced to be 30 mm and the distance between Nd:YVO4 rod and KTP crystal is only 1mm. Self Q-switched laser pulse at 532 nm with high peak power of 96 W, pulse width of 88 ns at FWHM and repetition rate of 400 kHz was achieved. Experimental studies of a passive Q-switched Nd:YVO4 laser using Cr:YAG crystal with three different transmissions of 30%, 40% and 70% were investigated. Passive Q-switched laser pulse at 1064 nm and narrow line width of less than 1.5 nm with highest peak power of nearly 18 kW, short pulse width of less than 4 ns at FWHM and higher repetition rate of 45 kHz using Cr:YAG with transmission of 30% was achieved for the first time.

Nd∶GdVO_4晶体生长及其1064nm的激光特性

本文报道了用 Ｃｚｏｃｈｒａｌｓｋｉ 方法生长 Ｎｄ∶ Ｇｄ Ｖ Ｏ４ 晶体，测量了该晶体的偏振吸收谱和荧光谱，表明晶体在８０８ ．５ｎｍ 有吸收峰，其发射波长在１０６４ｎｍ 。晶体中掺 Ｎｄ 浓度的原子分数为１ ．５６ ％ 的 Ｎｄ∶ Ｇｄ Ｖ Ｏ４ 的４ Ｆ３／２ 荧光寿命为１００μｓ 。用激光二极管泵浦１ｍ ｍ 厚的 Ｎｄ∶ Ｇｄ Ｖ Ｏ４ 晶体，得到了超过１ Ｗ１０６４ｎｍ 的输出光，泵浦阈值为２０ｍ Ｗ，光光转换效率为５５ ．９ ％ ，斜效率为６３ ％ 。

Nd^(3+):KGd(WO_4)_2激光晶体的研究

合成了一系列不同Nd3+ 浓度掺杂的Nd3+ :KGd(WO4 ) 2 粉末样品 ,进行了荧光光谱测试 ,初步确定了Nd3+ 的最佳掺杂浓度 ;测定了Nd3+ :KGd(WO4 ) 2 K2 WO4 生长体系的生长温度曲线 ,生长出尺寸达 50mm的Nd3+ :KGd(WO4 ) 2 优质激光晶体 ,切割出尺寸为 5mm× 5mm× 6mm的优质激光器件 ,采用钛宝石模拟LD泵浦 ,在 1.0 6 μm处得到 2 6 0mW的激光输出 ,斜率效率达到 6 6 % ;在 1.0 3μm处得到 135mW激光输出 ,斜率效率达到 34.3%。

Nd∶GdVO_4激光晶体的光谱性质和热学性质

用提拉法生长了Nd∶GdVO4单晶 ,测量了其室温吸收谱和室温荧光谱 ,测量了其热扩散系数α和比热CP,从而得到了其热导率λ。可以看到Nd∶GdVO4晶体的吸收波长在 80 8nm附近 ,与已经商品化的GaAlAsLD的发射波长能很好地匹配 ,从而增加了吸收效率 ,并且Nd∶GdVO4晶体具有较高的热导率 ,有望在高功率的激光系统中获得应用。所以Nd∶GdVO4晶体是理想的激光材料。

Nd^(3+)∶Gd_(0.2)Y_(0.8)Al_3(BO_3)_4激光晶体的研究

测定了Nd3+ ∶Gd0 .2 Y0 .8Al3(BO3) 4 -K2 MO3O10 B2 O3生长体系的生长温度曲线 ,生长出尺寸达32mm的Nd3+ ∶Gd0 .2 Y0 .8Al3(BO3) 4 激光晶体 ,并从中切割出尺寸为 4mm× 5mm× 6mm的优质激光器件 ,采用钛宝石模拟LD泵浦 ,在 1.0 6 μm处得到 4 8mW的激光输出 ,激光阈值 17mW ,光 光转换效率为 2 0 %。

氟化物激光晶体Nd^(3+)∶LiY_F4的坩埚下降法生长

晶体Nd3 +∶LiYF4是一种优良的LD泵浦激光工作物质 ,该晶体主要采用提拉法生长 ,迄今尚未见采用坩埚下降法生长该晶体的研究报道。本研究组进行了氟化物激光晶体的坩埚下降法生长工艺的研究 ,获得了大尺寸的激光晶体Nd3 +∶LiYF4。本实验采用氟化物试剂LiF(CP)、YF3 (AR)、NdF3 (AR)为初始原料 ,并用高温氟化法对氟化物原料进行脱水处理 ,以获得能满足晶体生长需要的无水氟化物原料。根据体系相平衡关系 ,晶体配合料的最佳组成应为LiF∶YF3 =5 1 .5∶48.5 ,同时考虑到在晶体Nd3 +∶LiYF4中Nd3 +是通过替代Y3 +而进入晶格的 ,确定按化学式Li5 1.5 Y47.5 Nd1.0 F4所示组成配制晶体配料 ,其中激活离子Nd3 +的掺杂浓度为 1mol%。在装填坩埚之前 ,将配料再次进行氟化处理 ,并烧结成多晶料。选用铂坩埚的尺寸为2 8× 2 5 0mm ,将籽晶放置于坩埚下端并填装配料后 ,焊接坩埚两端以隔绝空气 ,使晶体生长在密闭条件下进行。该晶体生长所用的坩埚下降生长炉采用电阻加热和铂 铂铑热电偶测温 ,控制炉温 92 0～95 0℃ ,生长体系的固液界面温度为 81 9℃左右 ,界面的温度梯度为 2 0～ 30℃ ,坩埚下降速度为0 .4～ 0 .8mm/h。在上述条件下已生长出尺寸达2 5mm× 6 0mm的透明、浅紫色、无散射的Nd3 +∶LiYF4晶体。