窄线宽1064 nm光纤激光泵浦高效率中红外3.8μm MgO:PPLN光参量振荡器

采用放大1064 nm掺镱光纤激光器作为泵浦源,实现了中红外3.8μm MgO:PPLN光参量振荡(OPO)激光输出。在泵浦源中,采用分布式反馈激光器(DFB)作为种子源来实现光纤激光窄线宽的调制,实现线宽2.5 nm到0.1 nm的压缩,最大平均输出功率可达40 W。进一步对不同泵浦线宽条件下中红外3.8μm MgO:PPLN OPO激光进行研究,最终在泵浦功率为18.1 W、线宽为0.1 nm、重频为1 MHz、脉宽为2 ns时,获得了最高平均输出功率为2.06 W的3822.5 nm激光输出,光-光转换效率为11.38%,光束质量为M2=2.34,提高了窄线宽泵浦对中红外MgO:PPLN OPO激光输出效率。     

Thermodynamic parameters of solids at high pressures from vibrational spectroscopy: MgO and MgAl2O4

Abstract

The effect of pressure on the optical or acoustic modes in the sideband fluorescence of Cr³⁺ doped into the MgO and MgAl₂O₄ lattices was identical to that measured for the corresponding Raman and infrared modes of MgAl₂O₄ and ultrasonic sound velocities (Chang and Barsch 1973, Jackson and Niesler 1982) for both MgO and MgAl₂O₄. This shows that the impurity cation does not measurably perturb the crystal lattice vibrations and thus may be used to probe the thermodynamic properties of such cubic materials at high pressures. The effect of pressure on the heat capacity, C_V, and entropy, S, of MgO and MgAl₂O₄ spinel was determined using statistical thermodynamics on the lattice vibrations measured to over 200 kbar. The results for MgO are identical to predictions from Debye theory to at least 10% compression.     

Cobalt-doped magnesium oxide pressure-transmitting medium for high pressure and high-temperature apparatus

ABSTRACT

Magnesium oxide (MgO) doped with cobalt (Co) semi-sintered pressure-transmitting medium (MCOPM) was prepared at 1200°C in air, starting with a pre-compressed mixture of MgO and cobalt oxide (CoO). The samples were characterized using powder X-ray diffraction, scanning electron microscopy, and thermal conductivity measurements. The results demonstrate that during the sintering process, the exchange of metal ions between the mixture powders introduced lattice defects into the MgO lattice structure, and an MgO–CoO solid solution was formed. Compared to commercial semi-sintered MgO pressure-transmitting medium (SSMPM), the temperature-generation efficiency of MCOPM-17 (MgO?+?17?mol% CoO) improved by about 220% at the high pressure of 12?GPa with a cell assembly in a two-stage multi-anvil large volume press. Moreover, the thermal conductivity of CoO-doped MgO decreased with increasing CoO doping.     

基于Talbot效应的掺镁铌酸锂二维六角位相阵列光栅的研究

本文系统研究了基于泰伯效应(Talbot) 的位相可调掺镁铌酸锂二维六角位相阵列光栅及其光衍射成像, 对光栅占空比D、不同位相差Δφ、及泰伯分数β条件下的光栅近场光衍射强度分布进行了理论研究, 结果表明当光栅占空比D=52%、位相差Δφ=0.75 π、 泰伯分数β=0.2时, 光栅近场衍射光图像效果最佳. 实验设计与 制备了掺镁铌酸锂二维六角位相阵列光栅, 并对其进行了Talbot衍射光成像实验研究, 得到了不同位相差和不同泰伯分数β条件下光栅近场衍射 光图像, 实验结果与理论研究结果相符. 关键词： 二维六角位相阵列光栅 掺镁铌酸锂晶体 泰伯效应     

Luminescence of [Be] centre in MgO:Be

Doping of MgO single crystals with Be results in the formation of numerous Be-containing paramagnetic centres, easily detectable by EPR, and creates an intensive luminescence band at 6.2 eV, observable at T<200 K, and gives rise to new thermoluminescence peaks at 147 and 190 K. A paramagnetic centre with a rhombic symmetry that decays at 160 K was identified as a [Be]⁺ (i.e. O⁻–Be²⁺) centre—a hole trapped by O²⁻ lattice ion near a Be²⁺ perturbing defect. The luminescence excitation and isochronal annealing studies led to the conclusion that the 6.2 eV luminescence arises at the radiative decay of electron excitations near Be²⁺. These excitations can be created at the recombination of electrons with the holes localised in the [Be]⁺ centres, at the recombination of holes with the electrons trapped in the Be¹⁺ centre or at a direct excitation of oxygen near the Be²⁺ ion.     

Experimental observation of vibrations produced by pulsed laser beam in MgO:57Fe

We report the first observation of a laser-produced vibration with the aid of Mössbauer techniques. Thin platelets of MgO single crystals were doped by diffusion of ⁵⁷Fe atoms. The illumination of the MgO:⁵⁷Fe sample with a pulsed Nd:YAG laser produced a significant broadening of the Mössbauer spectrum. In order to find out what caused these changes, we performed a series of time-domain experiments, in which the Mössbauer spectra were collected only during a 2.5 μs gate interval. This gate interval was swept from 5 μs to 190 μs over the time interval between the two laser pulses. After laser irradiation, the position of the Mössbauer line was found to be changing in time as a decaying oscillations of well-defined frequency, which can be due to the vibration of the sample induced by the laser pulse.     

Structural and electronic properties of hydrated MgO nanotube clusters

Hydrated MgO nanotube clusters are constructed and studied by the density functional theory at the B3LYP/6-31G(d) level. A strong exothermicity chemisorption reactivity of MgO nanotube clusters with water, which releases 137.5–171.8 kJ/mol. The averaged charge of Mg ions is steady, and presents a stronger ionic bonding. Mg ions are more sensitive to the coordination number. For the reaction of water onto clusters, electronic properties of hydrated clusters have remarkable change compared with anhydrous clusters.     

掺镁铌酸锂亚微米结构畴反转的研究

研究了掺镁铌酸锂(MgO：LiNbO₃)的极化特性及其畴壁运动的性质,通过调节多个脉冲外加电场来控制畴壁的运动,在背向反转效应作用下,反转畴发生劈裂,制备出均匀的掺镁铌酸锂亚微米周期畴结构,并分析探讨了掺镁铌酸锂亚微米结构的成因及其反转机理. 关键词： 亚微米畴结构 掺镁铌酸锂 背向反转     

Si衬底上磁控溅射法生长MgO薄膜

我们用射频磁控溅射方法,在Si(100)单晶衬底上生长MgO薄膜,借助X射线衍射(XRD)分析发现,我们获得了两种不同晶体结构的MgO薄膜,分别是常规的晶格常数为0.421nm的MgO薄膜和晶格常数为0.812nm的新结构的MgO薄膜.我们研究了溅射气压、衬底温度等工艺参数对两种晶体结构择取的影响.实验表明,高的溅射气压和高的衬底温度有利于晶格常数为0.812nm的新结构的MgO相的形成.在高的气压和温度下,我们制备出了晶格常数为0.812nm,具有很好的4次对称性的MgO外延薄膜.利用原子力显微镜(AFM)研究了这种薄膜的表面形貌.     

氧化镁薄膜的腐蚀速率研究

研究了以氧化镁（MgO）为牺牲层材料制作热成像阵列器件过程中MgO膜层在磷酸溶液中的湿法腐蚀特性，包括横向腐蚀速率和纵向腐蚀速率，获得了MgO膜层的腐蚀速率随磷酸溶液浓度和温度变化的关系曲线，并得到了用于制作图形和制作悬空结构的较好工艺参量.