含Co_6Ag_(94)三明治结构的光学和磁光性质

利用隧穿机制研究了含磁光金属Co6Ag94的三明治结构(磁光金属嵌入两个磁光光子晶体中)的透射性质和磁光法拉第旋转效应。在含磁光金属的三明治结构中,分别研究了双透射峰和单透射峰两种情况。研究结果表明,无论是双透射峰还是单透射峰情况,局域在磁光金属和磁光光子晶体界面上的电磁场,都能够同时增强磁光金属的透射和磁光法拉第旋转效应。另外,分析了磁光金属Co6Ag94存在增益时该三明治结构法拉第旋转角达到-45°的情况,此性质为设计小型化的磁光隔离器件提供了理论依据。     

含Co_6Ag_(94)三明治结构的光学和磁光性质EI北大核心CSCD

利用隧穿机制研究了含磁光金属Co6Ag94的三明治结构(磁光金属嵌入两个磁光光子晶体中)的透射性质和磁光法拉第旋转效应。在含磁光金属的三明治结构中,分别研究了双透射峰和单透射峰两种情况。研究结果表明,无论是双透射峰还是单透射峰情况,局域在磁光金属和磁光光子晶体界面上的电磁场,都能够同时增强磁光金属的透射和磁光法拉第旋转效应。另外,分析了磁光金属Co6Ag94存在增益时该三明治结构法拉第旋转角达到-45°的情况,此性质为设计小型化的磁光隔离器件提供了理论依据。     

一维磁光子晶体的法拉第效应

由于一维磁光子晶体能同时展示出很好的光透射率和法拉第旋转,故可用于实现小尺度的磁光隔离器。采用传输矩阵法研究了由磁光膜(Bi∶YIG)和电介质膜(Ta2O5,SiO2)构成的一维磁光子晶体,分别讨论了在垂直入射和斜入射条件下的法拉第效应,并给出了几种可行性结构,对磁光隔离器件的进一步改进设计具有一定的参考价值。     

一维磁光光子晶体的光学特性研究

详细推导了光在斜入射情况下通过磁光介质的4×4传输矩阵,研究了一维磁光光子晶体的光学特性.研究表明,由于光强主要局域在磁光介质层,波长位于光子禁带长波长带边的光通过磁光光子晶体所产生的法拉第旋转角比短波长带边产生的法拉第旋转角大得多.当光以TM偏振入射时,随着角度增大带边光产生的法拉第旋转角逐渐减小;而在TE偏振情况下,带边光产生的法拉第旋转角却随着角度的增大逐渐增大.     

一维磁性光子晶体的电磁场分析和数值计算

本文探讨一维磁性光子晶体的概念和结构.提出了一种分析一维磁性光子晶体的法拉第旋转效应的电磁场方法.分析计算表明:嵌于光子晶体中的一层很薄的磁性材料将可获得比单独一层同样厚度的磁性材料大得多的法拉第旋转效应,从而从理论上验证了文献上的相关实验.同时也分析了一维磁性光子晶体用作光子晶体结构下的光隔离器等器件中的法拉第旋转器的可能.     

BiCaInVIG磁光晶体的筛选与处理

对于法拉第光隔离器,其内法拉第旋转器所采用的磁光晶体的光学性能直接决定了光隔离器的性能。从透射光谱、设计波长透射率、镀制增透膜等方面对BiCalnVIG磁光晶体的筛选与．处理进行了研究。     

一维磁光子晶体实现光隔离的应用研究

采用4×4传输矩阵法研究了两种结构一维磁光子晶体的光隔离特性.结构一在外加磁场与光路光轴方向呈52.0°时,用7.96μm的总厚度在中心波长附近0.95nm范围内实现了光隔离,在此范围之内法拉第旋转角和透射率分别在45°~50.65°和97.01%~99.96%之间波动,结构仅包含43层光学薄膜,易于实际制备;结构二在外加磁场与光路光轴方向呈32.7°时,用11.54μm的总厚度在中心波长附近0.85nm范围内实现了光隔离,在此范围之内法拉第旋转角和透射率分别在45°~48.55°和98.85%~100%之间波动,结构包含73层光学薄膜,与结构一相比,该结构具有更高的透射率和更平坦的光谱.用这两种结构的一维磁光子晶体代替目前商用磁光隔离器中的块状磁光介质,可实现磁光隔离器的集成化.     

磁光光子晶体结构的法拉第效应增强

在超薄薄膜的基础上,基于时域有限差分法原理,利用FDTD Solutions仿真软件分别研究了基于两种多层膜结构和一种金属光栅结构的磁光光子晶体法拉第旋光效应。研究表明,多层膜结构的法拉第旋光效应增强原理为入射光在薄膜中心层的透射谱谐振,而金属光栅周期结构的法拉第效应增强是通过金属光栅激发表面等离子体实现的;在三种结构中,金属光栅周期结构具有更广的法拉第偏转角增强域。进一步通过参数优化,实现对金属光栅周期结构工作波长的可调节性研究,为薄膜型磁光器件设计提供了理论依据。     

磁光克尔效应中的光子自旋分裂

光子自旋霍尔效应类似于电子系统中的电子自旋霍尔效应, 是在折射率梯度和光子分别扮演的外场和自旋电子的角色下, 由自旋-轨道相互作用而产生的光子自旋分裂现象. 光子自旋霍尔效应为操控光子提供了新的途径, 同时也提供了一种精确测量相关物理效应的方法. 本文研究了磁光克尔效应中光子自旋分裂现象, 建立了磁光克尔旋转与光子自旋霍尔效应之间的定量关系, 并通过弱测量系统观测了磁场作用下铁膜表面的光子自旋分裂位移, 得到相应的磁光旋转角, 验证了我们所推导的理论预测. 本文的研究成果为精确测量磁光克尔系数和磁光克尔旋转角提供了一种新方法.     

多缺陷结构的一维磁光多层膜隔离器

由磁光介质（M）和电介质（G）周期性排列构成的磁光光子晶体会出现很强的光 局域性，最近用它来实现磁光隔离器引起人们广泛的兴趣.给出了一种可用于计算 偏振光在各向异性介质传播问题的传输矩阵方法.并用该方法计算了对称多缺陷结构磁光多 层膜隔离器的光学性质，发现随着缺陷数目的增多，旋转角及透过率的频谱响应得到改善. 当缺陷增加到一定数目时，不需要额外的反射层即可实现反射型磁光隔离器的要求. 关键词： 光隔离器 磁光效应 多层膜 光子晶体     

Magneto-optical activity of a one-dimensional photonic crystal with a magnetic defect

The influence of a magnetic defect on the field distribution and magneto-optical properties of a one-dimensional photonic crystal has been investigated. It has been shown that the maximum localization of the wave field in the defect layer is achieved in an asymmetric photonic crystal structure. A greater Faraday rotation, which significantly exceeds the angle of rotation of the polarization plane in an isolated magnetized layer, and a higher degree of localization of the wave field can be achieved when the magnetic layer is surrounded by layers of photonic crystal mirrors with a lower refractive index. An increase in the Faraday rotation angle is determined not only by an increase in the thickness of the magnetic defect but also by a symmetric increase in the number of periods in the photonic crystal mirrors.     

Reciprocity of Faraday effect in ferrofluid: Comparison with magneto-optical glass

The transmission light intensity method is carried out on a classical platform to study the reciprocity of Faraday effect in water-based Fe₃O₄ ferrofluid and its diluents. Setting the polarization direction of the analyzer at an angle of 45° to that of the polarizer, the switchable DC magnetic field and the alternating magnetic field are imposed to ferrofluid. The ferrofluid film is replaced by magneto-optical glass for contrastive experiments. The results indicate that ferrofluid is different with magneto-optical glass. Even though the direction of magnetic field is reversed, the rotation direction of the polarized light does not change for ferrofluid. The theoretical model of magneto-optical rotation was used to describe the origin of the reciprocity of Faraday effect in ferrofluid and the non-reciprocity in magneto-optical glass. These findings suggest that the magnetic moments of nanoparticles in ferrofluid tend to the same orientation with the magnetic field because of the rotation of particles.     

Far infrared Faraday rotation effect in one-dimensional microcavity type magnetic photonic crystals

The far infrared transmittances and Faraday rotation effect in one-dimensional photonic crystals that contain magnetic microcavities are calculated with the transfer matrix method. The different stacking sequences of dielectric layers in the magnetic photonic crystal are considered in this paper, and the linewidths of transmission peaks and localised light of the photonic crystals are discussed. The enhancement of Faraday rotation is presented in the magnetic photonic crystals, and the largest rotation angle at the frequency of the transmission peak is 29 °mm⁻¹, which is larger than previous results.     

Optical study of three-dimensional magnetic photonic crystals opal/Fe3O4

Optical and magneto-optical properties of three-dimensional magnetic photonic crystals, based on magnetite Fe₃O₄ embedded into an opal film matrix, are investigated in both transmission and reflection. A strong enhancement of the polar Kerr effect and a modification of the Faraday effect have been found near the photonic band-gap of about 1.8 eV. Unusual changes of hysteresis curves and their dependence on photon energy have been revealed in the spectral region where the magneto-optical effect reverses its sign. This phenomenon has been explained by two types of magnetite particles inside the opal matrix having different coercive fields and spectral behaviour.     

Magnetooptical effects in metal-dielectric plasmonic systems

Enhancement of magneto-optical effects in two-layer systems composed of perforated metal and magnetized dielectric films is theoretically predicted. The transmission and magneto-optical effect spectra of such systems are calculated and the conditions are determined that make it possible to enhance the Faraday effect by an order of magnitude in comparison with homogeneous magnetized films.     

Multicolor filter all-garnet magneto-optical photonic crystals

We demonstrate a multicolor optical filter and isolator based on a double-cavity magneto-optical (MO) photonic crystal. Being grown as a heteroepitaxial all-garnet multilayer, it compromises a strong MO response and high optical transmittance. Low-loss, high Faraday rotation passbands as well as strong light rejection within the stop band were achieved by optimization of distance between cavities and repetition number of distributed Bragg reflectors.     

交变磁场下法拉第效应研究

介绍了交变法拉第效应的磁光调制测量原理和方法，分析了亚铁磁材料法拉第Ｆｒａｄａｙ效应和磁光调制深度与交变磁场频率间的关系，证明了交变法拉第旋转幅值θ０的实部θ０小于静磁场下的θ＇ｓ，而虚部θ＇＇０大于θ＇＇ｓ，理论和实验结果相吻合，由此得出结论，采用具有磁圆二向色性的磁光材料做成的调制器不可能达到彻底的开关状态。     

Structure and magneto-optical properties of fine-grain garnet thin films

The structure and magneto-optical properties of fine-grain garnet thin films crystallized by the rapid recurrent thermal annealing (RRTA) method have been studied. The RRAT method has been used to crystallize BiGaDyIG garnet single-layer or BiGaDyIG/AI double-layer films and to get nanometer grain size (about 30–50 nm), which results in a large Faraday rotation angle, a smoother surface and fewer voids in the films. Meanwhile we have discovered that the Faraday rotation angle increases with the number of recurrences during the rapid annealing and quenching. With the more recurrent annealing one can not only get a strong Faraday effect, but it suppresses the appearance of DyFeO₃ phase in garnet films, which has been explained very well. By applying the new method, the as-deposited films have been succesfully crystallized to the (BiDy)₃(FeGa)₅O₁₂ garnet phase. They exhibited excellent magneto-optical properties with a coercivity of about 1500 Oe and effective Faraday rotation angle of 1.5°. The composition, magnetic and magneto-optical properties of the crystallized garnet films have been examined.     

Quantum theory of the magneto-optical effect induced by Ni ions in barium ferrites

To reveal the physical origin of the giant magneto-optical enhancement of Ni²⁺ ions in barium ferrite, quantitative calculations of the contributions of both the intra-ionic electric dipole transition between the 3d⁸ and 3d^{7 4p} configurations of the Ni²⁺ ions and the intra-ionic electric dipole transition induced by odd-parity crystal field terms are presented. It is deduced that the transition is important in the origin of the considered magneto-optical enhancement. The most important factor is the Ni-Fe superexchange interaction; since it is strong enough, the Faraday rotation produced by the Ni²⁺ ions is large though the energy difference between the 3d⁸ and 3 d7 4 p configurations is large. It is demonstrated that though the intra-ionic electric dipole transition does produce Faraday rotation peaks in the visible range, their magnitude is too small to explain the observed Faraday rotation. The effect of the spin-orbit interaction on the Faraday rotation is analysed. The spin-orbit interaction of the ground configuration plays a very important role in the occurrence of Faraday effects, but the Faraday rotation does not increase linearly with the strength of the spin-orbit coupling. On the contrary, the spin-orbit interaction of the excited configuration has almost no effect on the Faraday rotation. It is shown that the mixing of the different multiplets of the ground term induced by the crystal field has a great influence on the magneto-optical properties. Received 7 January 1998     

Growth-induced magnetic anisotropy behavior in thin garnet films fabricated by pulsed laser deposition

The effect of target rotation rate on the magneto-optical properties and induced magnetic anisotropy of pulse laser deposition grown Bi:YIG garnets has been investigated. The rotation rate dependence of magnetic properties of thin films has been studied using magneto-optical Faraday rotation combined with magneto-optical Kerr measurement setup. Our results show that decreasing the target rotation rate can also increase the polar coercive field and hence magnetic anisotropy. Also the spectral answer of samples show the capability of use of them in one off optical ranges such as visible, near infrared and far infrared regions.