Growth,Optical Properties and Defects of High-Doped Yb∶YAl_(3)(BO_(3))_(4) Crystal

High-doped Yb∶YAl_(3)(BO_(3))_(4)(Yb∶YAB)crystals were grown by the flux method using K_(2)Mo_(3)O_(10)as the flux.The efficient segregation coefficient was measured by using EPMA.The absorption and fluorescence spectra was measured at room temperature and compared the spectral parameters with Yb∶YAB of other Yb^(3+)concentrations.With the increase of the Yb^(3+)concentration,the main absorption and fluorescence peaks almost do not change,but the absorption coefficient and FWHM increase.The defects were investigated by using chemical etching method.The main defects are cracks,inclusions,dislocations and twins,which of them are more than low-doped crystals.

Crystal Growth,Spectroscopic Properties and Energy Levels of Cr^(3+):Li_2Mg_2(MoO_4)_3

This paper reported the crystal growth and spectroscopy characters of Cr^3＋：Li2Mg2（MoO4）3. The refractive index of Cr^3＋：Li2Mg2（MoO4）3 crystal is 1.87 and the hardness is 270 I-IV. This crystal shows broadband absorption property with peak wavelength at about 495 and 699 nm. The absorption crosssection is 14.75 × 10^-20 cm^2 at 495 nm and 9.63 ×10^-20 cm^2 at 699 nm, respectively. The crystal field strength and energy levels of Cr^3＋ ion were calculated based on the spectroscopic data. The Cr^3＋：Li2Mg2（MoO4）3 crystal shows broadband emission extending from 750 to 1300 nm even excited at 10 K. The room temperature emission cross section is 72×10^-20 cm^2 at 926 nm. A discussion of the relation between the spectroscopic properties and crystal field parameters of Cr^3＋：Li2Mg2（MoO4）3 crystal was presented based on the solid state spectroscopytheory.

Three-dimensional photonic crystals containing designed defects achieved with two-photon photopolymerization

Two-photon photopolymerization （TPP） with femtosecond laser is a promising method to fabricate threedimensional （3D） photonic crystals （PCs）. Based on the TPP principle, the micro-fabrication system has been built. The 3D woodpile PCs with rod space of 2000 nm are fabricated easily and different defects are introduced in order to form the cross-waveguide and the micro-laser structure PCs. Simulation results of the optical field intensity distributions using finite-difference time domain （FDTD） method are given, which support the designs and implementation of the PC of two types in theory.

Influence of SiO_3^(2-)Impurity on the Optical Properties of KDP Crystal

In this paper,potassium dihydrogen phosphate（KDP） crystals were grown in the presence of a series of silicate（SiO32-） impurity concentrations via conventional temperature cooling and rapid growth methods,respectively.It revealed that the SiO32-impurity could lead to the decrease of transmittance at the region of ultraviolet band for pyramidal sectors and slightly increased the transmittance for prismatic sectors.SiO32-could enter into the crystal lattice and create lattice defects,which consequently increased the density of light scatter.The decrease of laser damage threshold was attributed to the lattice defects and the redundant electrons brought by the replacement of SiO32-at the PO43-position.

Grown-in Defects of InSb Crystals:Models and Computation

In this paper,we present a model for grown-in point defects inside indium antimonide crystals grown by the Czochralski(CZ)technique.Our model is similar to the ones used for silicon crystal,which includes the Fickian diffusion and a recombina-tion mechanism.This type of models is used for the first time to analyze grown-in point defects in indium antimonide crystals.The temperature solution and the advance of the melt-crystal interface,which determines the time-dependent domain of the model,are based on a recently derived perturbation model.We propose a finite difference method which takes into account the moving interface.We study the effect of thermal flux on the point defect patterns during and at the end of the growth process.Our results show that the concentration of excessive point defects is positively correlated to the heat flux in the system.

Optical and scintillation properties of Ce:Y_(3)Al_(5)O_(12) single crystal fibers grown by laser heated pedestal growth method

The single crystal scintillating optical fibers acting as the scintillators and light conductors show potential application in scintillating fiber array detectors with high spatial resolution.In this paper we report the growth of 0.2 at%Ce:Y_(3)Al_(5)O_(12) single crystal fiber.The crystalline phase,surface morphology of the axialsection and cro ss-section,optical and scintillation properties of the as-grown fiber were investigated.The Ce:Y_(3)Al_(5)O_(12) single crystal fiber has a pure YAG phase,a uniform distribution of cerium in the axialsection and cross-section surface.Emission spectrum is composed of broad bands ranging from 440 to700 nm.In addition,the single crystal fiber has a high light yield of 26115±2000 photons/MeV,low energy resolution of 9.44%@662 keV and decay time of a fast component of 78 ns and a slow component of 301 ns.The intensity ratio of fast to slow components is roughly 8:1.

Analysis of heat transfer processes for sapphire growth by horizontal directed crystallization method

This research summarizes the analytical and experimental results of heat-transfer processes influence on defects formation during sapphire crystal growth by horizontal directed crystallization method(HDC).The shape of solid-melt interface significantly influences the process of sapphire crystals growth by this method.We receive the Stefan problem solution for sapphire crystals growth.It allows investigating the crystal growth process and the related factors(thermal stresses on different stages of growth process),their influence on defects formation.We investigate the main reasons for the formation of defective structures of the solid phase of sapphire crystals and the influence of thermal unit construction,the crystal geometry on the quality of the resulting sapphire crystal.We study the structure formation process,impurity distribution,and the nature of the defects in the crystal during it growth.

中长波Cr^(2+)/Fe^(2+)∶CdSe激光晶体生长及元件制备

本文采用自主研发的双温区真空石墨加热单晶炉,通过钼坩埚密封布里奇曼法成功生长出了Cr^(2+)∶CdSe晶体和Fe^(2+)∶CdSe晶体,晶体尺寸达Φ51 mm×110 mm。Cr^(2+)∶CdSe晶体和Fe^(2+)∶CdSe晶体分别在1400~2400 nm和2500~5200 nm波段存在明显的吸收,同时,Cr^(2+)∶CdSe晶体和Fe^(2+)∶CdSe晶体在7~15μm波段透过率均接近CdSe晶体透过极限(~70%),换算吸收系数约为0.005 cm^(-1)。采用钼坩埚密封布里奇曼法制备的Cr^(2+)/Fe^(2+)∶CdSe晶体具有过渡金属离子掺杂浓度可控、掺杂均匀、晶体品质高等优点,可同时作为中波红外激光晶体和长波红外非线性光学晶体材料。

坩埚下降法生长大尺寸Bi_(12)GeO_(20)晶体的宏观缺陷

Bi_(12)GeO_(20)晶体是一种多功能光电材料,在可见光范围内具有高速光折变响应,以及良好的压电、声光、磁光,旋光和电光等性能。目前,提拉法生长Bi_(12)GeO_(20)晶体,存在生长成本高、晶锭形状不规则、生长产率低、晶体光学质量差和有效晶体截面小等问题。本研究率先采用改进的坩埚下降法,在铂金坩埚和空气气氛中生长大尺寸Bi_(12)GeO_(20)晶体。通过各种分析测试方法研究生长获得的Bi_(12)GeO_(20)晶体中宏观缺陷的形态、分布和成分构成,探讨了晶体生长过程中主要宏观缺陷的形成过程和成因。坩埚下降法生长的Bi_(12)GeO_(20)晶体存在两种主要宏观缺陷:枝蔓状和管状包裹体。其中,枝蔓状包裹体与铂金溶蚀后的析晶相关,而管状包裹体与铂金析出、接种界面不稳定性和温度波动有关。本研究提出了消除坩埚下降法生长晶体中宏观缺陷的技术途径,通过降低生长控制温度、缩短高温熔体保持时间和优选籽晶等措施,可重复地生长光学质量良好、55 mm×55 mm×80 mm的大尺寸Bi_(12)GeO_(20)晶体,显著提升晶体的光学透过性能。

Nd,Y∶SrF_(2)激光晶体的位错缺陷表征及分布研究

氟化物激光晶体Nd,Y∶SrF_(2)(NYSF)具有热导率高、发射光谱宽、发射截面适中等特点,在高功率激光技术领域具有重要应用。激光晶体中的位错是反映其晶格完整性的一类重要的微观晶体缺陷,对晶体材料的力学、光学性能具有重要影响。本文采用坩埚下降法制备了NYSF激光晶体,分析了腐蚀实验条件对位错蚀坑形貌的影响,获得了化学腐蚀法研究NYSF晶体位错缺陷的最佳腐蚀工艺,即浓度为4 mol/L的盐酸溶液作为腐蚀液,腐蚀温度为60℃、腐蚀时间为9~12 min;表征了位错腐蚀坑形态的演变过程,探讨了晶格原子排列对位错蚀坑形态的影响;利用化学腐蚀方法表征了位错缺陷在晶体中的分布规律,即轴向分布为从放肩到尾部先减少后增加,径向分布为从中心到边缘逐步增加;分析了晶体生长条件对位错缺陷形成的影响,提出了位错密度随坩埚下降速率的提高而升高的可能原因。

氧化镓单晶在酸碱条件下的腐蚀坑形貌研究

氧化镓晶体材料由于其优异的性能以及可以用熔体法生长的优势,在功率器件、光电领域有着巨大的潜力。近年来,国内外众多专家也随之开展对氧化镓单晶材料的研究工作,高质量低缺陷的氧化镓单晶材料对后续的外延、器件的制备极其重要。目前,国际上主流的生长方法是导模法,导模法具有生长周期短、尺寸大及生长稳定等优点,然而在晶体缺陷控制方面还有很大的进步空间。本文围绕氧化镓单晶的腐蚀坑形貌,对导模法生长的氧化镓单晶进行加工制样,进行了不同酸碱条件下的腐蚀实验。详细介绍了观察到的不同腐蚀坑形貌,分析了晶体缺陷对腐蚀坑形貌的影响,对今后氧化镓单晶生长机理和晶体缺陷的研究具有重要意义。

Er掺杂CGA晶体的生长及浓度优化研究

本文采用激光加热基座法生长出一系列掺杂不同Er^(3+)浓度(摩尔分数)的Er∶CaGdAlO 4(Er∶CGA)激光晶体,并对制备出的系列晶体开展详细的光学性能研究。结合J-O理论计算和光学性能表征,通过对比吸收光谱中780~840和955~1020 nm的最大吸收系数、吸收截面、半峰全宽和辐射寿命等,以及荧光发射光谱的发射强度、发射截面和能级荧光寿命等光学性能参数,得到Er^(3+)的最佳掺杂浓度为5%。该工作为获得一种有望用于1.5~1.7μm近红外波段全固态激光器的新型激光增益介质提供了一定的实验基础。

激光加热基座法制备Er∶YAP单晶光纤及性能表征

本文采用了激光加热基座(LHPG)法逆向生长技术,实现了多组分Er∶YAP晶体的快速制备。利用LHPG法开展了Er∶YAP单晶光纤的生长研究,通过解决单晶光纤生长过程中存在的色心、开裂、直径起伏等关键问题,制备出直径0.8 mm、长度65 mm的高品质Er∶YAP单晶光纤。对不同掺杂浓度Er∶YAP晶体的光谱性能进行表征分析,结果表明掺杂浓度5%(原子数分数)时,Er^(3+)间存在较强的能量传递过程,有利于实现高效率中红外激光输出。

倍半氧化物晶体及其1~3μm波段激光性能研究进展

倍半氧化物具有优异的热学性能、稳定的物化性能、低的最大声子能量和强的晶体场,是理想的高功率、大能量激光基质材料。倍半氧化物具有超高熔点,因此其高质量、大尺寸的晶体制备极其困难,研究人员对此进行了长期的研究探索。近年激光技术发展对高品质倍半氧化物单晶的迫切需求促使相关晶体的生长技术取得了突破。本文在简单介绍倍半氧化物性能与结构的基础上,详细综述了Lu_(2)O_(3)、Sc_(2)O_(3)、Y_(2)O_(3)倍半氧化物晶体的生长方法及缺陷种类,系统总结了稀土离子掺杂的倍半氧化物在1~3μm波段内的激光性能,最后对其未来的研究与发展方向进行了展望。

RTP电光晶体的生长及其器件性能研究

磷酸氧钛铷(RbTiOPO4,简称RTP)是综合性能优异的电光晶体,具有电光系数高、半波电压低、激光损伤阈值高、器件小巧、环境适应性强等优点,已成为新一代电光器件应用材料,非常适合用作电光开关、电光调制器等。激光系统的发展迫切需求更高功率、更高重复频率和更窄脉宽激光用高性能电光晶体,基于此,本文选用富Rb的高[Rb]/[P]摩尔比值生长体系,通过顶部籽晶熔盐法生长出高质量RTP晶体,测试了晶体或器件的光学均匀性、重复频率、插入损耗、消光比和抗激光损伤阈值,结果表明,该晶体的光学均匀性为7.3×10^(-6)cm^(-1),重复频率为501 kHz,插入损耗为0.49%,消光比为31.57 dB,激光损伤阈值为856 MW/cm^(2)。

蓝宝石单晶光纤生长及性能研究

蓝宝石单晶光纤结合了蓝宝石单晶熔点高、物理化学性能稳定的性能特点和光纤长径比大的结构优势,在高温传感、辐射探测等领域得到了广泛的研究。本文通过激光加热基座(LHPG)法成功制备出高质量蓝宝石单晶光纤,其最小直径为50μm,具有极高的柔韧性。在此基础上系统研究了晶体取向、晶体直径、退火温度等因素对蓝宝石单晶光纤应力分布及力学性能的影响规律,所制备的蓝宝石单晶光纤抗拉强度超过3000 MPa,展现出了优异的力学性能。

大尺寸Tm∶YAP复合激光晶体的生长与性能研究

采用感应加热提拉法,通过改进热场、更换原料、二次熔接生长,直接生长出了直径大于40 mm的Tm∶YAP/YAP复合晶体毛坯。复合晶坯等径部分YAP段长21 mm,Tm∶YAP段长44 mm,晶坯外观完整,具有良好的光学均匀性和均匀的应力分布。绿光激光和He-Ne激光照射下,晶坯复合界面无散射、无气泡。复合界面两侧干涉条纹基本连续,透过波前差异小。从复合晶坯上加工出了直径5 mm、总长30 mm、端头不掺杂YAP晶体长4 mm的单端Tm∶YAP复合晶体元件,其光学质量优异。在1940 nm固体激光器上采用激光二极管单端泵浦进行了激光性能测试,在泵浦注入功率为117.7 W条件下实现了42.8 W激光输出,输出功率、转换效率和光斑质量均优于非复合激光晶体。

氧化铝单晶超声温度传感技术研究

针对航空、航天发动机温度测试过程中存在的传感器耐氧化性差、使用寿命短、测温精度低等迫切需要解决的问题。首先,采用超声导波测温原理,使用氧化铝(α-Al_(2)O_(3))单晶纤维作为超声波导,构建了超声温度测量系统。其次,对传感器的敏感元参数进行了设计,利用激光加热基座法生长的氧化铝单晶超声波导,制作了超声温度传感器。最后,对所制作的超声温度传感器进行了标定,在20~1800℃,传感器的灵敏度为0.44 m/(s·℃),重复性为95.27%。在模拟航空发动机测试平台上进行了测温实验,经分析该次测量合成不确定度为7.99℃。该方法为解决航空、航天发动机等恶劣环境下的温度测量,提供了新的途径。

Yb^(3+):CS-FAP激光晶体的生长研究

With the development of the diode laser pump sources,the Yb 3+ doped crystals have brought much attention which is not suitable for flash light pump source since they are not match in spectrum region.Comparing with Nd 3+ doped crystals,Yb 3+ doped crystals have many advantages,for example, (1)Yb 3+ doped crystals have very low thermal load,(only about 1/3 of that of Nd 3+ doped crystals) therefore,the systems can obtain lasers with higher optical quality and higher average power. (2)The energy stored up ability of Yb 3+ doped crystals is about 5 times as much as that of Nd 3+ doped crystals. (3)The position of main absorption peak of Yb 3+ matches to the pumping InGaAs diode emission,which is more durable than the AlGaAs diode used to pump the Nd 3+ . (4)The full width at half maximum of Yb 3+ doped crystals is 10 times as much as that of Nd 3+ doped crystals,so,the temperature control requirement of laser diode is relatively moderate. (5)From the point of view of energy transfer,because of the inherently small quantum defect of the Yb 3+ ,the theoredtical quantum efficiency can get up to 91%.

BGO 大单晶宏观缺陷的研究

应用光学显微镜、扫描电镜、电子探针、X 光衍射分析、原子吸收分光光度计等,对 BGO 大单晶生长中最常出现并严重影响晶体光学质量的宏观缺陷进行了研究。观察表明,晶体生长过程中,随生长条件的变化,这些宏观缺陷的形貌特征是不同的。本文对这些宏观缺陷的形成机理和克服方法进行了探讨,并在实践中得到良好效果。