端面抽运固体激光器中Nd∶YAG和Nd∶YVO_4晶体组合应用技术研究

采用Nd∶YAG与Nd∶YVO4晶体组合应用的方案,将具有优良导热和光电性能的Nd∶YAG晶体作为抽运光的前端吸收晶体,其后端放置具有较宽吸收谱的Nd∶YVO4晶体,用来吸收由于谱宽不匹配而没有被Nd∶YAG晶体吸收的抽运光能量成分。两种晶体在波长1064nm处的发射谱相互重叠,其吸收的抽运光能量可以转化成共同波长的振荡激光,提高了抽运光的利用效率。这种组合应用的方式还可以有效抑制振荡光功率随抽运源工作温度变化而产生的波动。实验证明,采用这种激光晶体的组合应用方案,相对于单一Nd∶YAG晶体方案,激光器的光光转换效率可提升22.9%,输出功率对温度的敏感度由7%降到1%以内。     

热容型板条激光器3种介质的温度和应力分布比较

阐述了热容型板条激光器重频工作方式下瞬态温度分布和热应力分布解析模型,对Nd∶glass,Nd∶YAG和Nd∶GGG3种介质的温度和热应力分布进行了数值计算和对比分析.结果表明:3种介质的温度分布和应力分布呈现相同的变化趋势.Nd∶glass的温度梯度比其他两者大,Nd∶YAG和Nd∶GGG温度变化非常接近;Nd∶YAG的应力较大,Nd∶GGG次之,Nd:glass最小,但三者差距不大.考虑到三者承受的最大断裂阈值,Nd∶GGG最好,Nd∶YAG次之,Nd∶glass较差.     

飞秒脉冲激光沉积钕掺杂薄膜特性研究

采用脉冲激光沉积(PLD)技术在Si(100)衬底上生长了Nd∶YAG薄膜以及Nd∶Glass薄膜,利用扫描电子显微镜(SEM)、能谱仪(EDS)、傅里叶变换红外光谱仪(FTIR)、光学掺量振荡器(OPO)以及光栅光谱仪等测试装置分析了薄膜的表面和断面结构形貌、组成成分、光学吸收谱以及光致发光谱。结果表明：在室温衬底温度下生长的Nd∶YAG薄膜以及Nd∶Glass薄膜均呈无规则非定型结构,没有明显的取向性微晶生长;PLD生长的Nd∶YAG薄膜中存在0.15 at.%化学计量比的Nd元素;Nd∶YAG块体靶材在750和808 nm有两个明显的吸收峰,而薄膜没有明显的吸收峰;Nd∶YAG薄膜在808 nm波长泵浦光下没有明显的光致发光谱峰,而Nd∶Glass薄膜在877和1 064 nm波长处有明显的光致发光谱峰。说明在室温衬底温度下生长的Nd∶Glass薄膜中Nd元素以Nd3+光学活性离子形式掺杂进玻璃基质中,而Nd∶YAG薄膜中的Nd元素没有以Nd3+光学活性离子形式掺杂进YAG基质中。     

Nd：YAG单晶光纤光学特性研究

本文测量了用激光加热基座法拉制的Nd:YAG单晶光纤(具有块状晶体)的吸收谱线,荧光谱线等光谱学特性.根据测得的散射特性分析了用该法拉制的单晶光纤的生长缺陷和直径波动及其与单晶光纤质量的关系.     

Nb∶KTiOPO4 CRYSTALS：PRODUCING BLUE COHERENT RADIATION AND 90° NONCRITICAL PHASE MATCHED SECOND HARMONIC GENERATION FOR Nd∶YAG 1.0642μm LASER

本文报道了用熔盐顶部籽晶法生长Nb浓度(0～13)mol%的Nb∶KTP晶体的倍频的Ⅱ型相位匹配的截止波长和Nd∶YAG 1.0642μm及Nd∶YA1O     

高浓度掺钕钇铝石榴石(Nd∶YAG)晶体的光谱与激光特性

测量了高掺杂浓度Nd∶YAG晶体的吸收光谱和荧光寿命。晶体的主吸收峰在 80 8nm处 ,Nd掺杂的摩尔分数为 0 0 30的Nd∶YAG晶体的吸收系数高达 2 0 7cm-1,荧光寿命为 15 0 μs,存在浓度猝灭。进行了钛宝石激光抽运高掺杂浓度Nd∶YAG和Nd∶YVO4 晶体的激光性能对比实验 ,所用Nd∶YAG晶体摩尔分数为 0 0 2 0和 0 0 2 5 ,激光斜率效率分别为 2 9 7%和 32 % ;Nd∶YVO4 晶体摩尔分数为 0 0 30 ,激光斜率效率为 34 7% ,表明了高浓度Nd∶YAG晶体在激光性能上与高浓度的Nd∶YVO4 晶体相当     

干涉条纹法测量LD端面泵浦Nd∶YAG热透镜焦距

研究了端面泵浦Nd∶YAG晶体热透镜效应,提出了一种新的测量热透镜的方法-干涉条纹法,并通过理论估算与用此方法所测的热透镜焦距相比较, 表明此方法所测热透镜焦距随着泵浦光功率的增大二者越来越吻合, 验证了该方法的可靠性. 该方法解决了端泵Nd∶YAG时, 由温度梯度, 热应力双折射和端面形变所引起的总的热透镜焦距难以测量的问题.     

915 nm单频Nd∶YAG晶体衍生光纤激光器

报道了一种基于Nd∶YAG晶体衍生光纤(NYDF)的915 nm单频光纤激光器.使用掺杂原子数分数为2.5％的Nd∶ YAG晶体作为纤芯材料,高纯度石英管作为包层材料,利用熔芯法制备Nd∶ YAG晶体衍生光纤,其传输损耗为8 dB/m,在915 nm处其增益系数为1.16 dB/cm.基于Nd∶YAG晶体衍生光纤,实现了一个稳定的915 nm单频光纤激光器,信噪比大于50 dB.实验结果表明Nd∶ YAG晶体衍生光纤有潜力应用于890～920 nm单频激光器.     

干涉条纹法测量LD端面泵浦Nd∶YAG热透镜焦距

研究了端面泵浦Nd∶YAG晶体热透镜效应,提出了一种新的测量热透镜的方法 干涉条纹法,并通过理论估算与用此方法所测的热透镜焦距相比较,表明此方法所测热透镜焦距随着泵浦光功率的增大二者越来越吻合,验证了该方法的可靠性 该方法解决了端泵Nd∶YAG时,由温度梯度,热应力双折射和端面形变所引起的总的热透镜焦距难以测量的问题.     

端面抽运激光晶体热形变及温度场分布研究

用有限元方法研究了端面抽运Nd∶YAG激光器中激光晶体的温度和端面热形变分布规律.研究表明,激光晶体的端面热形变分为端面伸长形变和鼓出形变两种,晶体的热形变透镜效应是由鼓出形变引起的.在端面抽运的Nd∶YAG晶体中采用第三类热传导边界条件,实验测量了晶体的端面伸长和端面鼓出形变,结果与理论分析相一致.     

Optical properties and laser performance of neodymium doped scheelites CaWO4 and NaGd(WO4)2

Nd-doped CaWO₄ (CWO) and NaGd(WO₄)₂ (NGWO) single crystals with good optical quality have been grown by the Czochralski technique. The neodymium distribution coefficient in these matrices is about 0.4 for CWO and close to unity for NGWO. Polarized absorption and emission spectra have been recorded at room temperature and used to calculate the absorption and stimulated emission cross-sections.1 and 2% Nd : CWO and 1 % Nd:NGWO laser rods have been tested in a cavity longitudinaly pumped by an 1 W AIGaAs laser diode and compared to Nd : YAG and Nd:YVO₄ rods in the same conditions. The 2% Nd: CWO rod exhibits the best performance with slope efficiencies of 64%, higher than in the case of YAG and equal to the YVO₄ samples. The dependence of the laser output power versus the diode temperature has been measured for all these materials. The laser output of Nd: CWO was found to be nearly as stable as for Nd : YVO₄ and much more stable than in the case of Nd : YAG. A CWO microchip has also been tested for the first time to our knowledge.     

In∶Nd∶LiNbO3晶体倍频性能的研究

在 LiNbO₃中掺进In₂O₃和Nd₂O₃, 以Czochralski技术生长了In∶Nd∶LiNO₃晶体. 通过光斑畸变法测得In∶Nd∶LiNbO₃晶体的光损伤阈值为1.98×104 W/cm², 比Nd∶LiNbO₃晶体的1.6×102 W/cm²高两个数量级以上;晶体吸收光谱的测试表明, In∶Nd∶LiNbO₃晶体的吸收边相对Nd∶LiNbO₃晶体发生紫移. 研究了In∶Nd∶LiNbO₃晶体的倍频性能, 结果表明, In∶Nd∶LiNbO₃晶体的相位匹配温度在室温附近, 倍频转换效率比Nd∶LiNbO₃晶体提高二倍.     

2-Phenylethylammonium p-hydroxybenzoate: Growth,structural, spectral,thermal, optical and mechanical characterization

An efficient nonlinear optical single crystal of 2-phenylethylammonium p-hydroxybenzoate (2PPHB) was grown from aqueous solution by slow evaporation solution growth method. Single crystal X-ray diffraction studies confirmed that 2PPHB crystallizes in orthorhombic crystal system with non-centrosymmetric space group of Pna2₁. The presence of functional groups in the synthesized compound was identified by FTIR spectral analysis. The grown crystals were thermally stable up to 155 °C. UV–vis absorption, photoluminescence and birefringence optical properties of grown crystal were explored. The laser induced surface damage threshold and relative second harmonic generation properties of the grown crystal were studied using Q-switched Nd:YAG laser. The variation of dielectric properties of the grown crystal with frequency was investigated for different temperatures. The mechanical response of the crystal was studied by Vicker's microhardness technique.     

Synthesis,growth and studies of undoped and sodium chloride-doped Zinc Tris-thiourea Sulphate (ZTS) single crystals

Single crystals of undoped (pure) and sodium chloride (NaCl)-doped Zinc Tris-thiourea Sulphate (ZTS) were grown from aqueous solutions by slow evaporation technique. Morphological alterations have been observed when NaCl is doped into ZTS crystals. Density of the grown crystals was measured by floatation method. The values of unit cell parameters from single crystal X-ray diffraction (XRD) studies show that pure and sodium chloride-doped ZTS crystals are in orthorhombic structure. Impurity concentration in the doped crystals was estimated by using an atomic absorption spectrometer. Second Harmonic Generation (SHG) test for the undoped and NaCl-doped ZTS crystals was performed by the powder technique of Kurtz and Perry using a pulsed Nd:YAG laser. Microhardness studies show that hardness number (H_v) increases with load for all the grown crystals of this work. From the values of work hardening coefficients, it is concluded that pure and sodium chloride-doped ZTS crystals belong to the category of soft materials. UV–vis–NIR spectra show that the grown crystals have wide optical transparency in the entire visible region. Birefringence studies of the grown samples have been performed by channelled spectrum method. The thermal stability of the materials is found to be increasing with the doping concentration of sodium chloride (NaCl) in the lattice of ZTS crystals.     

Growth,linear and nonlinear optical studies on guanidinium 4-nitrobenzoate (GuNB): An organic NLO material

Single crystals of guanidinium 4-nitrobenzoate (GuNB) were grown using solvent evaporation technique by mixing aqueous solutions of guanidine carbonate and 4-nitrobenzoic acid at ambient temperature. X-ray diffraction analysis characterized the unit cell parameters of the grown crystal and the crystal belongs to monoclinic system. The optical properties of the grown crystal have been studied by means of transmission measurements in the wavelength region between 200 and 1200 nm. The optical constants such as refractive index (n) and extinction coefficient (k) have been determined from the transmittance data. The optical band gap (E_g), the real and imaginary parts of the dielectric constant of the grown crystal was determined. Second harmonic generation (SHG) efficiency of the grown crystal has been studied using Nd:YAG laser and was measured as 3.2 times that of KDP. The low dielectric constant suggests the suitability of this compound material for NLO applications.     

Influence of Gamma-Ray Irradiation on Absorption and Fluorescent Spectra of Nd：YAG and Yb：YAG Laser Crystals

We investigate the influence of gamma-ray irradiation on the absorption and fluorescent spectra of Nd^3＋：Y3A15 O12 （Nd： YAG） and Yb^3＋ ： Y3A15 O12 （Yb： YAG） crystals grown by the Czochralski method. Two additional absorption （AA） bands induced by gamma-ray irradiation appear at 255nm and 340nm. The former is contributed due to Fe^3＋ impurity, the latter is due to Fe^2＋ ions and F-type colour centres. The intensity of the excitation and emission spectra as well as the fluorescent lifetime of Nd：YAG crystal decrease after the irradiation of 100 Mrad gamma-ray. In contrast, the same dose irradiation does not impair the fluorescent properties of Yb：YAG crystal. These results indicate that Yb： YA G crystal possesses the advantage over Nd： YA G crystal that has better reliability for applications in harsh radiant environment.     

Third order nonlinear optical properties of potassium dichromate single crystals by Z-scan technique

Single crystal of potassium dichromate (KDC) has been grown from aqueous solution by slow evaporation technique. The lattice parameters of the grown crystal were determined by X-ray diffraction analysis. The optical absorption studies reveal that the crystal has UV cut-off wavelength around 240 nm. Thermo gravimetric and differential thermal (TGA/DTA) studies revealed that the crystal thermally stable up to 397.1 °C. The mechanical strength of the grown crystal was carried out by Vickers micro hardness test. The crystal perfection was confirmed by etching studies. Third order nonlinear optical studies was performed using by single beam Z-scan technique using continuous Nd:YAG laser. Closed aperture Z-scan studies reveal the negative nonlinearity in the crystals and open aperture Z-scan reveals the saturation absorption. Also various parameters such as nonlinear refractive index n₂, absorption co-efficient β and nonlinear optical susceptibility χ⁽³⁾ were calculated for the grown crystal.     

Second harmonic chalcone crystal: Synthesis, growth and characterization

The novel nonlinear optical chalcone derivative (2E)-3-[4-(methylsulfanyl)phenyl]-1-(3-bromophenyl)prop-2-en-1-one (3Br4MSP) crystals have been grown by slow evaporation technique at ambient temperature. The crystal was subjected to different types of characterization method in order to study its possible application in nonlinear optics. The structure determination of the grown crystal was done by single crystal X-ray diffraction study. The morphology of the crystal is studied. The crystal was subjected to thermal analysis to find its thermal stability. The grown crystals were characterized for their optical transmission and mechanical hardness. The second harmonic generation (SHG) efficiency of the crystal is obtained by classical powdered technique. The laser damage threshold for 3Br4MSP crystal was determined using Q-switched Nd:YAG laser.     

铬、钕双掺钆镓石榴石(Cr~(4+),Nd~(3+))∶Gd_3Ga_5O_(12)激光晶体光学性能的研究

用提拉法生长了掺铬、钕的钆镓石榴石(Cr4+,Nd3+∶GGG)自调Q激光晶体。报道了室温下的吸收光谱和荧光光谱特性。分析了Cr离子浓度对光谱性质的影响。比较了Cr4+∶GGG,Nd3+∶GGG和(Cr4+,Nd3+)∶GGG晶体吸收光谱的关系。测量了(Cr4+,Nd3+)∶GGG晶体和Nd3+∶GGG晶体的荧光寿命,它们分别是33μs和250μs。实验表明,(Cr4+,Nd3+)∶GGG晶体是一种非常有潜力的自调Q激光晶体,可以实现大功率激光器的小型化和全固态化。