偶氮类有机材料光致双折射的测量

研究了2种偶氮聚合物薄膜的光致双折射效应,并探讨了泵浦光偏振态和光强对光致双折射的影响.采用远离共振区的He-Ne光(633nm)作为探测光,用Ar+激光(488nm)作为泵浦光,通过测量相关参量得到了样品的光致双折射值.实验结果表明:改变泵浦光的偏振态可以控制光致双折射值和探测光的透过信号强度,在0°～45°范围内,泵浦光光强存在最佳值,此时偶氮薄膜实验样品具有最大的双折射值.     

Unusual induction of optical anisotropy in polymer media by low-intensity polarized x-rays

The induction of linear dichroism in (poly) methylmetacrylate films activated with Rhodamine 6G and its base in the spectral range of absorption of these dyes under the action of plane-polarized x-rays with wavelength 0.70Å and intensity 7.5·10⁴ quanta per second has been revealed. The phenomenon is discussed from the standpoint of the radiochemical analog of the photochemical polarization-induced selection of organic molecules with allowance for the structural characteristics of the polymer film components.     

Optical properties of thin anisotropic films of polyethyleneterephthalate in the spectral range of 700–760 cm−1

Using transmission coefficients of anisotropic polyethyleneterphthalate films measured in the range of 700–760 cm⁻¹ the optical functions n(v) and χ(v) are calculated in the film plane and perpendicular to its surface. Its shown that the asymmetric broadenings and shift of the maximum of the absorption band at 727 cm⁻¹ in the case of oblique incidence of p-polarized radiation are due to the influence of optical anisotropy and dispersion. A. A. Kuleshov Mogilev State University, 1, Kosmonavtov Str., Mogilev, 212022, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol 66, No. 3, p. 409–412, May–June, 1999.     

Electro-optical properties and photopolarization anisotropy of methacrylic azopolymer films

We have synthesized polymethacrylates with azobenzene side moieties and “spacers” of different lengths. We have studied the spectra and kinetics of the electro-optical effect appearing in films of such azopolymers after they are exposed to linearly polarized light. The nature of the electro-optical effect is explained by the appearance of photoinduced optical anisotropy in the films, due to a change in the ratio of the concentrations of trans and cis isomers of the azobenzene moieties. The characteristic time required for establishment and relaxation of photoinduced optical anisotropy correlates with the times required for a change in the dielectric characteristics of the studied films when exposed to linearly polarized light. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 307–310, March–April, 2009.     

Optical anisotropy of magnetosome-doped polymer films

The anisotropy of several PVA/magnetosome magnetically textured films has been investigated. The thin film synthesized under the influence of a magnetic field (99 mT) shows the typical behavior of an anisotropic material. The results show that the magnetic field applied during the synthesis promotes an orientation of the chains of magnetosomes and permanent textured film is obtained after solidification.     

Theory and experiment for atomic optical filter based on optical anisotropy in rubidium

An atomic optical filter based on optical anisotropy induced by another left-circularly polarized pump field is theoretically and experimentally investigated in the 5S_1/2–5P_3/2–5D_3/2 ladder-type system of rubidium vapor. The filter displays a single peak transmission of 14.4% with 396 MHz bandwidth narrower than Doppler width. Furthermore, the variation of peak transmission versus pump intensity, pump detuning and cell temperature are also given. The theoretical and experimental results are in good agreement, which can enhance understanding of operation mechanism for this category of filter. The narrow-bandwidth filter is useful for free-space optical systems and laser spectroscopy.     

Photoinduced Birefringence in Poly(Methyl Methacrylate) Polymeric Thin Films Doped with Di-Azo Sudan G

Photoinduced birefringence in poly(methyl methacrylate) (PMMA), polymeric thin films doped with di-azo Sudan G was investigated. A pump-probe method was used to study the dynamic behavior of the birefringence. The mechanism for the inducement of birefringence is discussed in terms of the photoisomerization of the di-azo Sudan G molecules. The results showed that the dynamic evolution of the photoinduced birefringence was such that the average birefringence increased, saturated, and then decreased with respect to the laser pump intensity. Also, an exponential-like relationship was observed between both the saturation and the isotropic states of the averaged transmitted probe beam (expressing the residual anisotropy) and the birefringence on one hand, and the intensity amplitudes of the pumping powers on the other hand.     

二芳基乙烯光致各向异性动态特性研究

建立了光致变色二芳基乙烯样品光致各向异性动力学的理论模型.计算了在线偏振光激发下,二芳基乙烯分子数密度、光致二向色性和光致双折射随时间(曝光量)的动态变化曲线.结果表明,随着激发曝光量的增加,二芳基乙烯呈色态分子数密度不断下降直至饱和,光致各向异性随曝光量增加先增加,达到最大之后开始下降,最佳曝光量为260J/cm².利用正交偏振检测方法测量了反映材料各向异性的探测光透过率动力学曲线,并与理论计算结果进行了比较,二者基本相符. 关键词： 光致各向异性 二芳基乙烯 动态特性 最佳曝光量     

Polarization phase-shifting interferometer by rotating azo-polymer film with photo-induced optical anisotropy

A new type of phase-shifting interferometer was presented by rotating an azo-polymer film with photo-induced optical anisotropy in the light path of orthogonal polarization interferometry. By changing the angle of the optical axis of the azo-polymer film, four phase-shifted fringe patterns were obtained, from which phase difference between orthogonal polarized light could be calculated. The polarization states and the formation of the interferograms were analyzed theoretically using Jones matrix calculations and the experimental verification of the proposed method was also given. This method has a simple optical configuration which utilizes commercially available polarization devices and anisotropic azo-polymer film of low cost. The phase-shifting interferometer also demonstrates a new application of azo-polymer film.     

Co0.9Fe0.1薄膜面内元素分辨的磁各向异性

利用X射线磁性圆二色技术对Co_0.9Fe_0.1薄膜面内元素分辨的磁各向异性进行了研究，通过剩磁模式测量不同磁化方向的样品组分原子单位空穴磁矩的变化，发现除了在生长的磁诱导方向存在易磁化轴外，在与该轴垂直的方向还存在一个类似易轴的软磁化轴；面内的两个难磁化轴与易磁化轴取向大约成66°夹角，从而构成了面内双轴磁各向异性；对不同组分元素，其单位空穴磁矩随磁化方向的变化趋势基本相同，不同磁化方向Fe原子单位空穴的磁矩值约为Co的对应值的87%，反映了Fe原子和Co原子之间存在着强烈的铁磁性耦合. 关键词： 磁各向异性 X射线磁性圆二色 铁磁耦合 CoFe合金薄膜     

TiO2电子结构与其双折射性、各向异性 关联的理论研究

采用基于密度泛函理论的第一性原理平面波超软赝势方法对锐钛矿相TiO₂的晶体结构、能带结构、态密度等电子结构进行了理论分析, 在此基础上对介电函数、能量损失函数、光电导率等光学性质进行系统的理论计算, 分析了TiO₂双折射现象、各向异性与电子结构之间的关联, 其结果与文献报道的相关实验结果相符合, 从理论上探讨了TiO₂电子结构和其双折射现象、各向异性的特征.     

Origin of magnetization-induced anisotropy of magnetic films

It is proposed that the magnetization-induced anisotropy of magnetic films of cubic crystal structure originates from the anisotropy of atomic pair ordering, shape anisotropy, and strain anisotropy resulting from the constraint of the magnetostriction strain imposed on the film by the substratc. Calculated are the three anisotropy constants and their sum K vs temperature for Ni, Fe, and 55%Ni-Fe films; the room temperature （RT） constants vs the substrate temperature Tt during deposition or annealing after deposition for Ni and 50%Ni Co films; the RT constants vs com- position fraction for Fe-Ni films with Tt = RT, 250℃ and 450℃, Co Ni films at Tt = RT, 100℃ and 320℃, and Fe-Co films with Tt = RT and 300℃; the spread of RT K vs composition fraction for Fe Ni films; and RT △K/K vs composition fraction for Fe-Ni and Co Ni films, where △K denotes the variation of K of the film that is detached from its substrate. The calculated curves well accord with the measurements. The irrelevancy of K to the substrate material and the fast kinetics of the annealing in a field applied in the direction of the hard axis are explained reasonably.[第一段]     

一种新型偶氮化合物中的高效率实时全息光栅的实验研究

合成了一种新的含偶氮基的三元共聚物，由于在主链中链接柔性基团，使其具有相对较低的玻璃化温度，在６３３ｎｍ处光感生双折射δｎ值可达１０＾－３量级。实验上获得了几个乃至几百微米厚的具有高光学无效性的薄膜，在６３３ｎｍ波长处写一息光栅的实时单光束衍射效率可达１０％以上。     

Birefringent azopolymer long period fiber gratings induced by 532 nm polarized laser

Based on the photoinduced birefringence in azo materials, the model of the birefringent long period fiber gratings (BLPFGs) has been proposed and the transmission of such birefringent fiber gratings was further simulated by the coupled mode theory. In order to obtain the optimum condition for making birefringent azopolymer optical fiber (APOF) gratings the photoinduced birefringence of azo dye and methyl methacrylate (MMA) copolymers was systematically studied. After photosensitivity study of azo samples, using Teflon technique, azo dye containing single mode polymer optical fiber (POF) was fabricated. Finally, BLPFGs can be fabricated in azopolymer fiber using polarized 532 nm laser. A 120 μm LPFG with a 50% duty cycle has been successfully written within the core of the fiber with 532 nm laser by an amplitude mask method. Under polarized microphotography, the grating was observed when the optical axis was set at 45° with the direction of the first polarizing lens of the polarization microscope.     

铁磁/反铁磁双层薄膜中应力各向异性研究

采用铁磁共振方法,研究了铁磁/反铁磁双层薄膜中交换各向异性和应力各向异性对其物理性质的影响.结果表明,单向各向异性来源于界面交换作用,应力各向异性对材料的磁化难易程度有较大影响.当外磁场方向与应力场方向平行时,应力场的存在将促进该方向的磁化.反之,应力场将会阻碍该方向的磁化.     

吡咯俘精酸酐的光致各向异性研究

将有机光致变色化合物—吡咯取代俘精酸酐掺杂于PMMA中形成薄膜.在紫外光照射下,薄膜由无色态转换为呈色态.用650 nm线偏振激光照射薄膜,在由呈色态转变为无色态时产生光致各向异性.对633 nm的探测光具有正单轴晶体特性,光轴方向平行于激发光振动方向,光致二向色性率(D_⊥-D_∥)可达0.2,光致双折射率(n_∥-n_⊥)可达2×10^-3.实验还测量了光致各向异性与曝光量的特性曲线,发现最佳曝光量为13～20 J/cm²;理论分析了其原因.这些结果为俘精酸酐材料在光信息处理方面的应用提供了实验数据.     

Giant optical anisotropy in semiconductor heterostructures with no-common atom

Due to their reduced symmetry no-common atom heterostructures are expected to present in-plane anistropic features. We report polarization-resolved optical transmission measurements performed on GaInAs–InP multi-quantum wells evidencing a large dichroïsm. A linear dependence of this anistoropy on an electric field has also been observed, giving rise to the quantum confined Pockels Effect. All these intrinsic results which are forbidden by the usual envelope function theory compare fairly well with the predictions of the recently proposed model.     

光纤几何路径引起的圆双折射

本文对单模光纤中线偏振面的旋转与光纤几何路径的关系进行了研究.首次报道了在光纤入射端和出射端不平行的情况下的数值计算和实验测量结果.     

m面GaN平面内结构和光学各向异性研究

采用金属有机物化学气相淀积方法在铝酸锂LiAlO₂衬底上外延生长m面GaN薄膜.X射线衍射测量的结果表明所得薄膜具有较理想的m面晶体取向,并对其各向异性的应变进行了计算,摇摆曲线的测量发现样品存在明显的面内结构各向异性.采用偏振光致发光研究材料的面内光学各向异性,发现随着偏振角度的改变,发光峰的峰位和强度均有明显变化,并用对称性破缺导致价带子带劈裂的理论对结果进行了解释. 关键词： m面GaN 结构各向异性 偏振光致发光