MgF2-Based Luminescing Ceramics

Russian Physics Journal - Results of investigation at 300 K of photo- and cathodoluminescence of the high-temperature optical ceramics synthesized for the first time based on MgF2 activated...     

氟化镁整流罩的高速抛光

整流罩在高速飞行中对空气进行整流 ,并同时起光学窗口的作用。热压多晶氟化镁常用作整流罩材料。但在加工中发现 ,这种材料易出现散射颗粒 ,严重影响零件的表面质量。通过高速抛光工艺的摸索 ,提高了零件的表面质量 ,缩短了抛光时间 ,提高了生产效率。     

Optical switching applications of ZnSe/MgF2 photonic band gap structures based on thermal nonlinearities

We investigate a thermo-optical device based on a ZnSe/MgF₂ multilayer and demonstrate the modulation of its optical reflectance around the band edge. An electrically induced temperature increase is responsible for the change of the refractive indices of the layers. As a result, the reflection spectrum shifts and the reflected signal decreases. The structure was grown using a thermal evaporation technique, and was designed in such a way that a band edge appears at 632.8 nm, i.e. accessible to a low-power He–Ne laser. The reflection characteristics were investigated as a function of the applied voltage and we found that the photonic band edge shifts by a maximum of 7 nm for an applied voltage of 90 V. Furthermore, different sets of measurements have shown that the spectral shift depends on the voltage squared, thus allowing experimental data analysis in terms of the thermally driven optical nonlinearity.     

Color centers in irradiated MgF2

Abstract

Color centers in rutile-structured MgF₂ single crystals irradiated at 20K/360K by reactor neutrons are investigated spectroscopically at LNT. Four different types of the F-F vacancy bond in MgF₂ are possibly identified to the observed absorption bands as due to the F₂ centers; instead of previous assignments, the 300nm band to the F₂(D_2h), the 325nm band to the F₂(C₁), the 355nm band to the F₂(C_2v), and the 400nm band to the F₂(C_2h) centers.     

MgF2单晶的THz光谱研究

利用THz时域光谱技术对MgF2晶体(样品1)和MgF2:Co晶体(样品2)在0.5-2.5THz的吸收特性进行了研究.在0.5-2.5 THz波段,样品1吸收系数α(ν)随频率ν增加而增大,最大值为24 cm-1.样品2的吸收系数比样品1大得多,Co掺杂使晶格吸收带边向低频移动,而且样品2在1.9THz有吸收峰,吸收系数达到70 cm-1,由此求出F--Co2+离子键伸缩振动的键力常数K为3.40×10-2 N/cm.这一结果表明,THz光谱分析有可能成为研究晶体化学键的一种重要手段.利用光学常数之间的关系计算了两个样品在0.5-2.5 THz的介电函数的实部ε1(ν),得到样品1的ε1(ν)值在4.67至4.73之间,样品2的ε1(ν)值在4.62至5.01之间.     

BaMgAl10O17:Eu2+的MgF2表面包覆

采用溶胶-凝胶法对蓝色荧光粉BaMgAl10O17:Eu2 (BAM)进行表面包膜处理,获得了表面均匀包覆MgF2膜层的BAM荧光粉.并用SEM、XRD和IR手段对其表面形貌、晶格结构性能进行了表征;用EDS对BAM粉体的表面元素进行了定性分析;用荧光光谱测试对荧光粉的发光性能进行了研究.结果表明,在BAM粉体表面均匀包覆MgF2层后,BAM的晶格结构,发光性能没有改变,初始亮度较未包覆的荧光粉有所降低,经过相同条件的热处理后,包覆MgF2荧光粉的亮度热衰减程度明显低于未包覆的荧光粉,且色坐标偏移现象不明显.     

Heavy ion induced damage in MgF 2 crystals

MgF 2 single crystals were irradiated with 22 Ne and 238 U ions in the energy range 31-2642 v MeV. The ion-induced damage was studied by optical spectroscopy, scanning force microscopy, and volume expansion measurements. The efficiency of damage creation depends on the stopping power (d E /d x ) and the fluence of the ions. Out-of-plane swelling and the formation of hillocks on the crystal surface require a critical d E /d x of approximately 3 v keV/nm. The efficiency for creation of simple defects (color centers) and of more complex damage (swelling, hillock formation) in MgF 2 is compared with the corresponding efficiency in LiF.     

Energy of Frenkel' defect formation in MgF2

Russian Physics Journal -     

Elektrische Quadrupolwechselwirkungen von20F im MgF2-Einkristall

Polarized²⁰F nuclei (T _1/2=11s,I=2) have been produced in a tetragonal MgF₂ single crystal by capture of polarized neutrons. Nuclear magnetic resonance transitions have been induced and observed via the asymmetricΒ decay to²⁰Ne, yielding the quadrupole coupling constant ¦e ² q Q/h¦=5.77(2)MHz, the quadrupole moment ¦Q(²⁰F)¦=0.064(12) b and the asymmetry parameter of the electric field gradientη=0.317(2). In order to study possible lattice defects produced by the recoil displacement due to the captureγ-rays NMR signals were registered both at room temperature and at 12 K. Width and depth of the resonance curves indicated that at room temperature nearly all²⁰F ions occupy normal lattice sites with an undisturbed environment. At 12 K, however, where no annealing occurs, this is only true for about half of the²⁰F ions which are stopped directly at defect free sites. The other half of the²⁰F ions at 12 K shows resonance frequencies shifted by defect interactions up to the order of some 100 kHz. Furthermore two simple methods are reported which allow a quick estimate of the strength of the quadrupolar interaction: (1) observation of theΒ decay asymmetry versus the magnetic field strength (decoupling curve), (2) broad-band modulation of the inducedrf field and observation of theΒ asymmetry versus the depth of the modulation.     

MgF2:Mn2+合成及发光

本文首次报导了采用碱式碳酸盐和氟化铵一步合成MeF2:Mn2+长余辉材料新方法。研究了各种条件和Mn2+浓度对荧光粉的影响,所得到的MgF2:Mn2+发射为橙红色,主峰在590nm,色度值为x=0.559,y=0.438,余辉大约200ms。荧光粉呈现均匀圆球状的颗粒,属于四方晶系。     

Excited-state absorption of Co2+ in MgF2 and KZnF3

We report on measurements of excited-state absorption spectra and absolute cross-sections in Co²⁺-doped KZnF₃ and MgF₂ at room temperature in the near-infrared domain. The data are compared with the predictions of the single-configuration co-ordinate model.     

Localized Second Optical Harmonic in Nonlinear Optical Ceramics Excited by a Femtosecond Laser

Optics and Spectroscopy - Second harmonic generation is studied in samples of LiTaO3 powder ceramics with different lithium concentrations (48.8 and 49.3%) under excitation by a femtosecond laser...     

Al和MgF2多层滤光膜光谱及其环境稳定性

采用真空热蒸发和电子束蒸发方法,制备了Al和MgF2 多层滤光膜,并在100,150,200, 300 ℃的真空环境中进行了热处理,考察了真空热处理温度对多层滤光膜光谱、形貌和环境稳定特性的影响。结果表明,经过真空热处理后,滤光膜表面粗糙度降低,峰值透射率升高,半宽度增大。随着在实验室干燥环境中放置时间的增加,未热处理以及300 ℃热处理样品的透射率峰位向长波方向有较大的移动,峰值透射率降低,可见光抑制特性减弱。而150, 200 ℃热处理样品的透射率峰位移动很小,峰值透射率及可见光抑制特性基本保持不变,具有很好的环境稳定性。     

MgF2晶体的激光损伤与加固研究

报道了ＭｇＦ２晶体１．０６μｍ激光损伤阈值和损伤形貌。研究了用ＣＯ２、ＸｅＣｌ和Ｃｕ蒸气三种不同的激光对ＭｇＦ２进行激光预辐照加固和酸腐蚀加固。结果表明，Ｃｕ蒸气激光加固效果最佳，蕨是酸腐蚀和ＸｅＣｌ激光预辐照，并对加固机理进行了分析。     

真空紫外铝+氟化镁膜偏振特性的研究

研究了铝＋氟化镁膜在真空紫外波段的偏振特性。理论上数值模拟计算了铝＋氟化镁膜在真空紫外波段的反射率及其与入射平面平行和垂直两方面的分量，分析了铝＋氟化镁膜反射率的两分量随入射条件和氟化镁膜厚度的变化规律，在此基础上研究了铝＋氟化镁膜的偏振特性，并与单层铝膜的相应特性作了比较，以氟化锂堆作偏振器，在Seya-Namioka真空紫外反射率计上实验研究了铝＋氟化镁膜的偏振特性。研究结果表明，铝＋氟化镁膜的偏振特性由于受到氟化镁厚度的调制，存在反射率的垂直分量小于平行分量的情形，从而使铝＋氟化镁膜的消光比在非正入射的条件下接近1。理论计算结果与实验结果一致。     

沉积温度对热舟蒸发MgF2薄膜性能的影响

 采用热舟蒸发方法沉积了氟化镁(MgF₂)材料的单层膜,沉积温度从200 ℃上升到350 ℃,间隔为50 ℃。测量了样品的透射率和反射率光谱曲线,进行了表面粗糙度的标定,并在此基础上进行了光学损耗及散射损耗的计算。同时对355 nm波长处的激光诱导损伤阈值进行了测量。结果表明:随着沉积温度的升高,光学损耗增加;在短波长范围散射损耗在光学损耗中所占比例很小,光学损耗的增加主要由吸收损耗引起;在355 nm波长处的损伤阈值变化与吸收损耗的变化趋势相关,损伤机制主要是吸收起主导作用。样品的微缺陷密度也是影响损伤阈值的一个重要因素,损伤阈值随缺陷密度的增加而降低。     

Al和MgF2多层滤光膜光谱及其环境稳定性

 采用真空热蒸发和电子束蒸发方法,制备了Al和MgF₂ 多层滤光膜,并在100,150,200, 300 ℃的真空环境中进行了热处理,考察了真空热处理温度对多层滤光膜光谱、形貌和环境稳定特性的影响。结果表明,经过真空热处理后,滤光膜表面粗糙度降低,峰值透射率升高,半宽度增大。随着在实验室干燥环境中放置时间的增加,未热处理以及300 ℃热处理样品的透射率峰位向长波方向有较大的移动,峰值透射率降低,可见光抑制特性减弱。而150, 200 ℃热处理样品的透射率峰位移动很小,峰值透射率及可见光抑制特性基本保持不变,具有很好的环境稳定性。