Er:YCOB和Er:Yb:YCOB晶体的光谱分析

分别测量了Er YCOB晶体和ErYb YCOB晶体的室温吸收光谱.讨论了Yb3+离子对Er3+离子的敏化作用.     

LiNbO_3:In:Fe:Cu晶体中的双波长非易失存储

为了提高晶体的非易失存储性能,采用双波长存储技术实验研究了LiNbO3:In:Fe:Cu晶体中的非易失存储,折射率调制度为1.04×10-4,记录灵敏度达到0.965 cm/J.与传统的双色非易失记录相比,该方法大幅度地提高了光栅的强度和记录的灵敏度.利用Kukhtarev带输运模型对双波长非易失记录过程中光栅的动态演化过程进行了数值模拟,同时讨论了氧化还原程度对双波长非易失全息记录的影响.理论与实验符合的较好.     

非晶态异质结构a-Si:H/a-SiN_x:H和a-Si:H,a-SiN_x:H薄膜的应力研究

实验发现在一定Si—H键浓度下,相对于平坦的硅衬底而言,在其上沉积的a-Si:H薄膜具有压缩应力,a-SiN_x:H薄膜具有伸张应力。当a-Si:H和a-SiN_x:H层厚度比近似于1:2时,硅衬底上生长的a-Si:H/a-SiN_x:H/c-Si样品,弯曲最小,并能保持很长时间。文中还给出了应力随退火变化的情况,并对实验结果进行了讨论。     

双掺Nd:Ce:YAG晶体激光输出特性

 为提高固体激光器的能量利用率,增大输出能量,将双掺Nd:Ce:YAG晶体的输出特性与普通Nd:YAG晶体进行了对比研究。分析了Nd³⁺和Ce³⁺的吸收光谱对激光晶体初始阈值反转粒子数的影响,结果显示:双掺Nd:Ce:YAG晶体可以提高晶体对泵浦光能量的利用率及激光器的输出能量,且可降低阈值泵浦能量。并分别检测了Nd:Ce:YAG激光晶体与Nd:YAG晶体的输出激光能量和阈值泵浦能量,实验结果表明：在输入电压为750 V时,Nd:Ce:YAG晶体与Nd:YAG晶体的输出能量分别为651.5 mJ 和390.4 mJ,能量利用率分别为2.31%和1.38%,激光振荡需要的泵浦能量阈值分别为10.56 mJ和15.21 mJ,且普通Nd:YAG晶体的斜效率为0.36%,而双掺Nd:Ce:YAG晶体的为0.49% 。     

论:英才教育

 我国著名物理学家王淦昌先生极为关心中学英才教育,多次与本刊主编探讨这一关系千秋大业的话题．他在年事已高、科研繁忙之时,还审阅了张大同先生的《论“英才教育”》一文,写下了极为重要的评语,这对搞好英才教育、培养栋梁之材有着积极作用。王淦昌先生审阅张大同先生此文的意见如下:“当此举国上下都在从事科技兴国的伟大事业时,很重要的一点:是要发现英才、培养英才,以为国家所用。兹介绍关于这方面有丰富经验因而有很大贡献的张大同同志(上海华东师范大学二附中物理学教师)的一篇文章。从这里可以得到启发,如何为国家培养出很多优秀的物理或其他学科的人才。”     

Kondo-lattice: Kondo-effect?

The periodics-d-model is investigated by Green function methods. We find that the lnT-divergence appearing in third order perturbation theory for the electron selfenergy is smoothed out but still shows up in a characteristic decrease (exchange coupling<0) or increase (>0) of lifetime of electrons at the fermi level asT0 and a corresponding structure in the specific heat. However, in contrast to the single impurity case, the corresponding characteristic temperature does not vary like exp[–1/||] but always is of order ². From a mean field theory of the model, one finds a critical temperature for a transition into a magnetically ordered stateT _c0 which varies precisely like ². Thus an interesting competition between Kondo-effect and long-range magnetic order can be expected in this model.Work performed within the research program of the SFB 125 Aachen/Jülich/Köln     

Photoluminescence studies of γ-irradiated CaF2:Dy:Pb:Na single crystals

The optical absorption (OA) and photoluminescence (hereafter referred to as luminescence) studies were made on CaF₂:Dy:Pb:Na single crystals (Dy—0.005 at%, Pb—0.188 at% and Na—0.007 at%) before and after γ-irradiation. The unirradiated crystal exhibited a strong OA band around 6.36 eV attributed to the ‘A’ band absorption of Pb²⁺ ions. The γ-irradiated crystal exhibited OA bands around 2.06, 3.28, 3.75 (broad shoulder) and 2.48 eV. The first three bands could be tentatively attributed to M_Na centre when compared with that of the coloured CaF₂:Na. The origin of 2.48 eV band was not explicitly known. Luminescence emission and excitation of Pb²⁺ and Dy³⁺ ions were negligible in the unirradiated crystal. Irradiated crystal exhibited a strong excitation spectrum with overlapping bands, due to different colour centres, in the UV-vis region for the 2.15 eV emission characteristic of Dy³⁺ ion. When excited, the absorbed energy (may be a part) was transferred from a colour centre to nearby Dy³⁺ ions and Dy³⁺ characteristic emission was observed. Exciting the irradiated crystal around 3.28 eV yielded emission at 2.56, 2.15 and 1.76 eV. The first two emission bands were due to Dy³⁺ ions. The excitation spectrum for the 1.76 eV emission showed two prominent bands around 2.02 and 3.08 eV and hence the emission was attributed to the M_Na centre. The luminescence mechanism was described.     

a-C:N:H纳米尖端荧光产生的机理

用CH4,H2和NH3为反应气体,利用等离子体增强热丝化学气相沉积在沉积有碳膜的Si衬底上制备了a-C:N:H纳米尖端,并用扫描电子显微镜和微区Raman光谱仪对碳膜和纳米尖端进行了表征。结果表明:Raman谱中含有与碳和氮相关的峰,且纳米尖端的Raman谱比碳膜的Raman谱有很强的荧光背景。Raman谱中的峰说明沉积的碳膜和纳米尖端是a-C:N:H薄膜和a-C:N:H尖端。a-C:N:H纳米尖端的Raman谱中强荧光背景的产生表明其在激发光源照射的过程中发射了强荧光,对a-C:N:H纳米尖端产生强荧光的机理进行了探讨。     

双掺杂LiNbO3:Fe:Mn全息存储动力学

建立了包括扩散、漂移和光伏打效应三种输运机制,小信号光强、小调制度近似下描述双掺杂LiNbO3:Fe:Mn晶体用双色光进行全息存储的动力学的耦合微分方程组,数值求解并解释了晶体光存储的时间动态发展过程.在此基础上,分析了晶体的氧化还原程度对全息存储过程的影响,只有在晶体总的受主数密度Na(即Fe3+和Mn3+的数密度之和)大于铁离子数密度N2的条件下,双掺杂LiNbO3:Fe:Mn晶体全息存储才能达到非破坏性存储的目的.经过光固定的光栅的衍射效率随氧化增大,光折变灵敏度随氧化而减小,要获得高衍射效率就必须以降低光折变灵敏度为代价.在掺铁浓度一定的情况下,掺锰浓度越高,能实现信息长期存储对应的氧化还原状态的有效动态范围越大.     

非晶态异质结构a-Si:H/a-SiNx:H和a-Si:H,a-SiNx:H薄膜的应力研究

实验发现在一定Si—H键浓度下,相对于平坦的硅衬底而言,在其上沉积的a-Si:H薄膜具有压缩应力,a-SiN_x:H薄膜具有伸张应力。当a-Si:H和a-SiN_x:H层厚度比近似于1:2时,硅衬底上生长的a-Si:H/a-SiN_x:H/c-Si样品,弯曲最小,并能保持很长时间。文中还给出了应力随退火变化的情况,并对实验结果进行了讨论。 关键词：     

Optical spectroscopy and diode-pumped laser characteristics of codoped Tm-Ho : YLF and Tm-Ho : BaYF : a comparative analysis

Single crystals of monoclinic BaY₂F₈ and tetragonal LiYF₄ codoped with the same Tm³⁺ and Ho³⁺ concentrations were successfully grown by the Czochralski method. Here we present a comparative analysis of the two hosts including spectroscopic characterization and cw diode-pumped laser experiments in the 2-μm wavelength region at room temperature. The main differences between the two hosts are a lower slope efficiency associated with a much wider tuning range (2005–2094 nm) of BaY₂F₈ with respect to LiYF₄. Received: 29 July 2002 / Published online: 11 December 2002 RID="*" ID="*"Corresponding author. Fax: +39-050/2214-333, E-mail: toncelli@df.unipi.it     

高电导a-Si:H:Y合金的电输运特性

本文报道由rf溅射技术将稀土元素Y掺入非晶硅,当掺Y浓度为20％左右时,获得了室温直流电导率为2×10¹Ω^-1·cm^-1的a-Si:H:Y合金膜。测量表明该合金膜是n型。变温电导测量指出,在测量温度范围内lnσ与l/T的关系可拟合于两条直线。对于衬底温度为260℃,290℃和330℃溅射的合金膜,其转折点分别出现在～70℃,～75℃和～90℃。这表明a-Si:H:Y合金膜存在两种电传导机制:在室温附近电子在Y施主杂质带内跳跃传导,在高温情况下电子在导带延展态内传导。并且得到Y施主杂质带中心处于导带E_c以下0.06—0.07eV。 关键词：     

LiNbO3:Cr:ZnO晶体生长和光谱特性的研究

采用提拉法从近化学计量比的熔体中生长出尺寸为φ20 mm×50 mm的优质LiNbO3:Cr:ZnO(CZLN)晶体,其光学均匀度为7.59(10-5).进行了吸收和荧光光谱的测定研究.吸收谱测试表明:Cr3 离子在晶体中有2个宽且强的吸收带及1个微弱的吸收线,两宽带中心波长分别为480和660 nm,对应于4A2→4T1和4A2→4T2两个具有相同的总自旋能级之间的跃迁,在4A2→4T2吸收宽带的长波边缘处有个很小的吸收峰,其波长为727nm,对应于4A2→2E(R线)的跃迁.荧光测试表明:当激发波长为660 nm时,CZLN晶体荧光宽带和1个较弱的荧光线峰并存,宽带范围为802～988 nm,峰值波长为871 nm,对应于4T2→2E,4A2的联合能级跃迁,荧光线峰波长约为754 nm,其强度较弱,相应于2E→4A2(零声子线)能级跃迁.计算了晶场强度和Racah参数,其Dq/B=2.72,晶体属于强场介质.研究表明,CZLN晶体具备可调谐激光晶体的基本光谱要求,且有良好的物化性能,可以实现宽频带可调谐激光输出.它又具有较大的倍频系数,有望实现420 nm附近紫外的自倍频激光输出.     

反应溅射a-Si:H/a-Ge:H超晶格的热稳定性

通过红外透射谱和X射线衍射谱研究a-si:H/a-Ge:H超晶格的热稳定性,发现当周期厚度较小时,超晶格的晶化温度比体膜a-Ge:H的大,对实验结果作初步讨论。 关键词：     

双掺杂LiNbO3:Ce:Cu晶体的光学性能

用提拉法生长出3种不同浓度的双掺杂LiNb03∶Ce∶Cu晶体,测试双掺杂晶体的红外吸收光谱、紫外可见光吸收光谱和X射线衍射谱,掺杂相对浓度较高时,紫外吸收边向长波方向红移,X射线谱峰半峰值宽度变小.测试掺杂晶体在生长态和氧化态时的衍射效率,氧化态的衍射效率比生长态衍射效率高,但响应时间较长.     

物理学咬文嚼字之二十一:Dimension:维度、量纲加尺度

英文dimension和measure同源.Dimension在中文物理学文献中以维度、量纲和广延度等不同的面目出现.然而,英文dimension出现的地方,其含义常常是多方面的,择其一而译之,难免有失偏颇.此外,dimension是重要的数学和物理学概念,dedimensionalization,dimensional analysis,fractal dimension,fractional-dimension calculus,dimension reduction,等等,都涉及重要的科学思想甚至是专门的学科领域.     

In:Fe:LiNbO3晶体的全息存储性能研究

在ＬｉＮｂＯ３中掺进Ｉｎ２Ｏ３和Ｆｅ２Ｏ３用恰克拉斯基法生长ｎ：Ｆｅ：ＬｉＮｂＯ３晶体,测试表明,Ｉｎ：Ｆｅ：ＬｉＮｂＯ３晶体抗光致散射能力高,响应速度快,存储保存时间长。研究了Ｉｎ：Ｆｅ：ＬｉＮｂＯ３晶体全息存储性能的机理,测得的衍射效率最大值为７３％。