K9玻璃低压下的双折射效应研究

研究K9玻璃在低压下的双折射效应,测量它的双折射率及其梯度。结果表明,当K9玻璃用作天文透镜材料时,应充分考虑其自重引起的对透镜光学性能的影响。     

光学平衡桥式电流互感器的设计

为了消除传感头随温度变化的线性双折射对光学电流互感器性能的影响,提出了光学平衡桥式电流互感器的概念,并给出了设计原理.推导了与温度有关的线性双折射导致的线偏振光方化角变化量的解析式,并计算了用1/2波片来消除线性双折射影响时波片光轴的方向.给出了光学平衡桥的工作原理和信号处理的方法,推导出计算电流的表达式.进行了实验研究,螺线管电流为2 A,温度在20℃-65℃范围变化时,所设计互感器的输出误差在2.96%以内.提出的光学平衡桥式电流互感器,解决了原有方法存在的线性双折射随温度变化对测量精度影响的难题,有利于促进光学电流互感器的实用化进程.     

考虑磁场对碰撞影响的等离子体输运过程

本文考虑了强磁场对碰撞过程的影响,用Bogoliubov方程来讨论强磁场中等离子体的输运过程。当分布函数随空间的变化比较缓慢、在Debye屏蔽距离内等离子体的密度、温度的变化可以忽略时,得到了计算强磁场中等离子体输运过程的一般方法。最后计算了沿磁场方向的电导率,电导率随磁场的增加而增加。在温度10~6K,电子密度10~(12)cm~(-3),磁场强度约为9T时,考虑磁场对碰撞影响所计算出的电导率,要比忽略磁场对碰撞影响所得结果大22.3％。     

弱双折射光纤布喇格光栅反射偏振对温度响应特性的研究

理论分析了切趾弱双折射光纤布喇格光栅反射偏振相关特性与温度之间的关系.数值模拟了切趾弱双折射光纤光栅的反射谱、偏振相关损耗和差分群时延随波长变化曲线.实验测出了不同温度下反射谱、偏振相关损耗和差分群时延随波长变化曲线.根据实验结果对偏振相关损耗和差分群时延的变化情况作出了分析.反射偏振相关损耗呈现两个峰值,随温度增加两峰漂移程度相同,表明偏振相关损耗无明显差异.差分群时延最大值随温度增加成线性向长波方向漂移,证明了光纤光栅正交模损耗变化的等同性.综合理论分析与实验结果表明:切趾弱双折射光纤布喇格光栅的偏振特性随温度产生明显的变化,其正交模变化呈现等比例特性.     

高功率法拉第隔离器多模退偏特性

理论分析了隔离器在高功率多模激光入射时的自退偏特性.结果表明:线性双折射致退偏与圆双折射致退偏均与入射光功率的平方成正比,线性双折射致退偏与光斑大小无关,而圆双折射致退偏随光斑半径的增大而减小.当光斑半径与旋转晶体半径相比很小时(R0/r0≥80)圆双折射引起的退偏大于线性双折射引起的退偏,当光斑半径接近旋转晶体半径(R0/r0≤3)时,与线性双折射引起的退偏相比,圆双折射引起的退偏可以忽略.对比单模激光入射,在同种条件下,多模入射使得线性双折射致退偏减小了0.4倍, 最小圆双折射致退偏减小为0.05倍.     

光纤光栅双折射效应的实验研究

本文对均匀光纤光栅和线性啁啾光纤光栅的双折射效应分别进行了实验研究. 利用压电陶瓷的压电效应实施对均匀光纤光栅和线性啁啾光纤光栅的侧向挤压, 使之产生双折射, 通过改变施加在压电陶瓷上的电压值, 可以实现对光纤光栅双折射大小的控制. 侧向挤压线性啁啾光纤光栅可以补偿光纤通信系统中的偏振模色散.     

线性双折射色散对OCS灵敏度影响的理论研究

以琼斯矩阵为数学工具,利用理论分析和计算机仿真的方法研究了线性双折射的色散特性及其对光学电流传感器灵敏度的影响. 在光学电流传感器系统中,光源的驱动电流与环境温度改变,都会造成光源峰值波长移动. 由于光学玻璃材料线性双折射的色散特性,会使光学电流传感器的灵敏度随光源波长的变化而改变. 研究结果表明,线性双折射的色散特性会对输出曲线的尺度因子产生影响,但是影响很小可以忽略. 本研究结果可为光学电流传感器的研究设计人员提供有用的参考.     

高功率法拉第隔离器多模退偏特性

理论分析了隔离器在高功率多模激光入射时的自退偏特性.结果表明：线性双折射致退偏与圆双折射致退偏均与入射光功率的平方成正比,线性双折射致退偏与光斑大小无关,而圆双折射致退偏随光斑半径的增大而减小.当光斑半径与旋转晶体半径相比很小时（R0/r0≥80）圆双折射引起的退偏大于线性双折射引起的退偏,当光斑半径接近旋转晶体半径（R0/r0≤3）时,与线性双折射引起的退偏相比,圆双折射引起的退偏可以忽略.对比单模激光入射,在同种条件下,多模入射使得线性双折射致退偏减小了0.4倍, 最小圆双折射致退偏减小为0.05倍.     

块体金属玻璃Zr46.75Ti8.25Cu7.5Ni10Be27.5的超导与负电阻温度系数

测量了块体金属玻璃Zr46.75Ti8.25Cu7.5Ni10Be27.5在退火前后其电阻值随温度的变化,测量的温度范围为1.5-300K.样品在退火前后都发现有超导现象.零磁场下其超导转变温度Tc分别为1.84和3.76K.在5-300K温度范围内,原始样品具有负的电阻温度系数.如果取Zr,Ti,Cu,Ni及Be分别贡献出1.5,1.5,0.5,0.5及两个传导电子,则可以用扩展的Faber-Ziman理论去解释原始样品的负电阻温度系数.还对块体金属玻璃Zr46.75Ti8.25Cu7.5Ni10Be27.5在温度范围5-300K之间的R(T)曲线用一个多项式进行了拟合.     

线性双折射对光纤电流互感器影响的研究

应用琼斯矩阵理论分析传感光纤中残余线性双折射对光纤电流互感器测量精度的影响。根据干涉结果得到在传感光纤中加入大量圆双折射可以抑制残余线性双折射,并提出有效的减小线性双折射误差的方法。     

Effects of the temperature features of linear birefringence upon the sensitivity of a bulk glass current sensor

The temperature characteristics of linear birefringence and its effect upon the output of a bulk glass current sensor is theoretically analyzed and simulated. The results show that when temperature field distributes evenly, the linear birefringence induced by the mutual pressure between sensing head and surrounding material of the package is the main factor, the sensitivity of the system could be varied more than 1% during changes of temperature within the range of −40–40 °C. These results might be useful to those studying optical glass current sensing techniques.     

Magnetic linear birefringence in Yb<Subscript>3</Subscript>Ga<Subscript>5</Subscript>O<Subscript>12</Subscript> gallate garnet

The magnetic linear birefringence and the magnetic susceptibility of Yb₃Ga₅O₁₂ gallate garnet was investigated experimentally in the temperature range 78–295 K. It was shown that, in this temperature range, the magnetic linear birefringence of the garnet studied depends linearly on inverse temperature 1/T. The magnitude of this effect is determined only by the part of the crystal magnetization that is due to the difference in the thermal population of the ground state of the Yb³⁺ ion rather than the total magnetization. The results obtained are interpreted within the microscopic theory. According to this theory, the magnetic linear birefringence is determined by the quadrupole moment of the magnetoactive ion, which is induced by an external magnetic field.     

Mössbauer spectroscopic study of a low temperature magnetic transition in ordered Fe-doped NiAl

Mössbauer spectroscopic (MS) measurements at ambient and cryogenic temperatures on powdered Fe-doped NiAl materials (Ni-40Al-9Fe and Ni-50Al-9Fe) exhibited paramagnetic behavior down to 17 K, with one Fe-site in the hosts. At 4.2 K, Ni-40Al-9Fe (Al deficient) remained paramagnetic, while Ni-50Al-9Fe (Ni deficient) displayed a magnetic transition, resolved in terms of one Fe environment. The internal magnetic field of the magnetically split site of Ni-50Al-9Fe was 185?±?8 kOe determined from a field distribution model. This shows that electronic and magnetic interactions in ordered Fe-doped NiAl depend on Fe site preference tendencies. The single Fe site observed at 4.2 K for the Ni-deficient alloy shows that its Fe distribution or site occupancy is not random but ordered. The interactions leading to the development of internal magnetic field in the Ni-deficient ordered alloy is temperature dependent being absent above 17 K based on MS measurements from ambient to 4.2 K.     

基于1556 nm光纤激光器频率分裂效应的应力测量

光学元件在红外波段的应力-光学常数是众多光学系统关心的问题之一.本文提出一种基于1556.16 nm掺铒光纤激光频率分裂效应的光学玻璃内应力致双折射测量方法.选择平面介质膜腔镜和光纤光栅(FBG)构成线形半开放式谐振腔,并分析了光纤自身弯曲引入谐振腔内的双折射.将待测光学玻璃附带力传感结构放置在谐振腔内,结合Jones矩阵传递方程得到了外载荷所致双折射与空腔双折射的叠加模型.对光学玻璃的载荷从0逐级递加到20 N,内腔的频率分裂量增加,根据双折射叠加模型和频率分裂原理解出应力与频率分裂量的对应关系,且该结果可溯源到基本物理量—波长.实验结果表明,系统灵敏度为22060 Pa/nm,线性度为99.44%,可广泛应用于红外波段的光学元件双折射精确测量.     

A quantum spherical <Emphasis Type="Italic">p</Emphasis>-spin glass model: Low-temperature behavior

Low-temperature slow dynamics, aging, and temperature and field shifts are studied analytically and numerically for a quantum p-spin (p = 3) glass model interacting with internal quantum environment and external magnetic fields. It is demonstrated that the correlation function and the real part of susceptibility are subject to aging and restoration (rejuvenation) under little changes of temperature and field. The examined effects are briefly analyzed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 42–48, January, 2007.     

环境温度对纳米磁流体场诱导光学双折射的影响

在20~80 ℃温度范围内,研究了两种浓度的铁氧体(主要成分为Fe3O4)磁流体在一系列固定磁场强度(场强范围为0~200 mT)下的双折射与温度的关系.结果表明不同浓度磁流体的双折射具有类似的磁场和温度依赖性.固定磁场强度时,磁流体的双折射值与温度成反比|而温度恒定时,磁流体的双折射值与外磁场的强度成正比|在相同磁场强度、恒定温度下,高浓度磁流体的双折射值比低浓度磁流体的大.详细分析了实验结果,并深入讨论了磁流体双折射的温度、场强和浓度依赖性的物理机理.     

Linear magnetic birefringence in the quadratic-layer antiferromagnet K2MnF4

The linear optical birefringence of the quasi-Heisenberg antiferromagnet K₂MnF₄ has been determined between 5 and 300 K. A large magnetic contribution (LMB) is found at temperatures below 200 K. According to the earlier results with the iron-group difluorides the LMB can be related to the magnetic internal energy. Below 30 K the LMB of K₂MnF₄ obeys a T³-law. The temperature derivative of the LMB follows a course expected for the magnetic heat capacity of pronounced two-dimensional systems: a broad, rounded maximum above the three -dimensional transition point. At T_N a kink occurs in the LMB.     

Magnetic short-range order in the linear-chain antiferromagnet CsMnCl3 · 2H2O studied by optical birefringence

The linear optical birefringence of CsMnCl₃ · 2H₂O shows a magnetic contribution due to one-dimensional short-range order. The temperature derivative of this part is proportional to the magnetic specific heat. For the intrachain interaction we find |J|/k = 3.13 ± 0.15 K. Around the Néel temperature the interchain coupling causes a small birefringence change with the opposite sign.     

Phenomenological analysis of the linear magnetic birefringence in dysprosium iron garnet

Experimental data on linear magnetic birefringence (LMB), previously reported at 1.15 μm wavelength in the 4.2-300 K temperature range and with an applied field up to 20 kOe, in dysprosium iron garnet (DyIG) are analyzed in terms of electric dipole transition within the three magnetic sublattices. Assuming that the garnet symmetry is cubic and that the contribution of the Fe³⁺ ions to LMB is the same as yttrium iron garnet (YIG), the 2nd order magneto-optical (MO) coefficient (Γ₂) of the Dy³⁺ ions is deduced. In the spontaneous state, Γ₂ is linear temperature dependent as previously found for the 1st order (MO) coefficient. It is shown that Γ₂ must be field dependent to explain the evolution of the LMB.     

Lineare optische anisotropie von antiferromagnetischem NiO im äusseren magnetfeld

Single crystals of NiO exhibit an optical anisotropy below their Néel temperature T_N = 523.7 K even without external magnetic fields. Linear dichroism and birefringence increase in proportion to the square of the antiferromagnetic long range order parameter. The spectra of both effects show detailed structures in the visible range: the dichroism exhibits a large peak at 2.12 eV and some smaller ones below and above; the birefringence increases steadily towards the fundamental absorption edge (3.75 eV); and, some structures are superposed in the visible range of the small 3d⁸-absorption bands. In external magnetic fields a large rise of the Néel temperature is detected by optical anisotropy. It is proportional to the square of the field strength: T_N(H) = T_N(O) + 0.585 K/Tesla². Below T_N optical anisotropy shows a slight magnetic field dependence. Our results are discussed by means of a microscopic model of the magneto-optical anisotropy in NiO.