磁光玻璃磁致旋光效应的研究

介绍磁致旋光效应和磁光玻璃磁致旋光效应的机理。对ZF1、ZF6磁光玻璃的磁致旋光效应分别进行了实验研究，给出偏振面旋转角与磁感应强度的关系．计算出波长不变情况下不同磁感应强度的费尔德常数。对实验数据进行了处理．并与理论预期值进行了比较．发现理论值与实验结果符合得较好。     

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.     

All-optical switch based on photonic crystal microcavity with multi-resonant modes

We present a design of all-optical switches based on one-dimensional photonic crystals (1D PhC) doped with nonlinear optical materials. The 1D PhC switch structure is composed of a PhC cavity sandwiched by two accessional PhC microcavities. The center PhC cavity has two resonant frequencies with nearly the same quality factors (Q), while the accessional PhC cavities have the same resonant frequency, which is equal to one of the resonant frequencies of the center cavity. The two accessional PhC cavities cause reduction of Q value in this resonant frequency and result in different Q values of two modes. We realize all-optical switch effect by selecting pump light wavelength at the low Q mode and probe light wavelength at the other mode. The theoretical simulations by using the finite difference time domain method show that the pump light intensity required to realize optical switch effect in the designed switch is 50 times smaller than that in one-dimensional photonic crystals cavity with only one resonant mode.     

Magneto-optic parametric oscillation

We develop a model of large-signal steady-state magneto-optic parametric oscillation in the Faraday configuration of a singly resonant cavity. The conversion efficiency and the threshold and phase-matching conditions are discussed, and we show that tunable phase matching can be achieved by use of a static magnetic field, eliminating any walk-off effects.     

Mixing of bound states with electron transport by a radiation field in waveguides

Electron transmission in the two-, three-, and four-terminal nanostructures is considered under the influence of a radiation field. The frequency of the radiation field is tuned to the transition between the energy of a bound state and the Fermi energy of the incident electrons. The radiation induced resonant peaks and dips of the electron transport are exhibited for zero and low magnetic fields. It is shown that rotation of the radiation field polarization can effectively control the electron transport into different electrodes attached to the structures because of the symmetry of the structures. The resonant anomalies of the Hall resistance are found in a weak magnetic field. Zh. éksp. Teor. Fiz. 114, 1954–1970 (December 1998) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

垂直入射条件下金属环的谐振特性

本文研究垂直入射条件下水平极化和垂直极化时金属开口谐振环(split ring resonator, SRR)的电磁响应行为. 通过分析这两种情况下的透射系数、介电常数和磁导率, 发现垂直极化时, SRR可以产生电谐振实现负介电常数, 其频段远高于磁谐振频段; 水平极化时, SRR只能产生磁谐振实现负磁导率, 其频段与水平入射时的SRR的磁谐振频段相对应. 通过仿真对此进行了证明, 并对产生电谐振和磁谐振的原因进行了分析.     

Tunable magnetoben-optic modulation based on magnetically responsive nanostructured magnetic fluid

Magnetic fluid is a kind of functional composite material with nanosized structure and unique optical properties. The tunable magneto-optic modulation of magnetic fluid under external magnetic field, achieved by adjusting the polarization direction of incident light, is investigated theoretically and experimentally in this work. The corresponding modulation depth and response time are obtained. The accompanying mechanisms are clarified by using the theory of dichroism of magnetic fluid and the aggregation/disintegration processes of magnetic particles within magnetic fluid when the external magnetic field turns on/off.     

Genetic optimization of magneto-optic Kerr effect in lossy cavity-type magnetophotonic crystals

We have demonstrated an optimization approach in order to obtain desired magnetophotonic crystals (MPCs) composed of a lossy magnetic layer (TbFeCo) placed within a multilayer structure. The approach is an amalgamation between a 4×4 transfer matrix method and a genetic algorithm. Our objective is to enhance the magneto-optic Kerr effect of TbFeCo at short visible wavelength of 405 nm. Through the optimization approach, MPC structures are found meeting definite criteria on the amount of reflectivity and Kerr rotation. The resulting structures are fitted more than 99.9% to optimization criteria. Computation of the internal electric field distribution shows energy localization in the vicinity of the magnetic layer, which is responsible for increased light-matter interaction and consequent enhanced magneto-optic Kerr effect. Versatility of our approach is also exhibited by examining and optimizing several MPC structures.     

Magneto-optics of antiferromagnets

Antiferromagnetic crystals in which crystallographic sites occupied by magnetic ions from various sublattices are not transnationally equivalent and are not associated with each other by a symmetry center can have magneto-optic properties distinct from the properties of other antiferromagnets. In particular, birefringence and dichroism of linear polarized light can be observed which are directly proportional to the magnetic field strength, as well as magnetic rotation and circular dichroism quadratic in the field strength. Both effect—the linear magneto-optic effect and quadratic magnetic gyration — are sensitive to the crystal magnetic symmetry and to reorientation of the antiferromagnetic vector. Both effects reverse their signs when the directions of the magnetic moments of a sublattice are changed. These properties of new magneto-optic effects can be used to study the time-reversed domain structure of antiferromagnets, to define the symmetry of magnetic ordering and to study the magnetic crystal energy spectra by spectroscopic methods. The results of experimental studies of the linear magneto-optic effect and quadratic magnetic rotation in tetragonal antiferromagnetic fluorides of transition metals, manganese-germanium garnet and other antiferromagnets are reported. Experimental results on the domain structure of high symmetric antiferromagnets, the point magnetic symmetry of non-collinear multisublattice antiferromagnetic garnet MnGeG are discussed.     

Magneto-optic fiber Sagnac modulator based on magnetic fluids

A magneto-optic modulator with a magnetic fluid film inserted into an optical fiber Sagnac interferometer is proposed. The magnetic fluid exhibits variable birefringence and Faraday effect under external magnetic field that will lead to a phase difference and polarization state rotation in the Sagnac interferometer. As a result, the intensity of the output light is modulated under the external magnetic field. Moreover, the modulator has a high extinction ratio and can easily be integrated in a single-mode fiber system. The performance of the modulator is not affected by ambient temperature variation from room temperature to 40 °C.     

Electric field patterns in finite two-dimensional wire photonic lattices

Electric field patterns in finite two-dimensional wire photonics lattices are investigated by means of electromagnetic simulations. These studies reveal a strong analogy with the envelope wavefunction approach extensively used for semiconductor superlattices. Several propagating eigenmodes in the pass-band of the periodic structure as well as evanescent modes in the stop-bands are clearly identified. They are interpreted on the basis of the matching of the wavelength of electromagnetic field to the lattice dimensions with an envelope wavefunction resulting of a Fabry–Pérot effect in the cavity formed by the periodic structure. In terms of transmission coefficient, the calculated frequency dependence are in agreement with those measured in finite metallic rod arrays between 50 and 110 GHz.     

Photochromism and magneto-optic response of ZnO:Mn semiconductor quantum dots fabricated by microemulsion route

ZnO:Mn semiconductor quantum dots were prepared by solution casting led microemulsion route. Quantum dots of average size ∼2 nm were noticed in transmission electron micrographs. The present work highlights colour change phenomena (photochromic effect) of quantum dots while subjected to photon illumination. The magneto-optic measurements e.g. magnetic field (H) vs angle of rotation (θ) show step like behavior and is ascribed to the quantum confinement effect of diluted magnetic ZnO:Mn nanostructures. Further, underlying mechanism responsible for exhibiting photochromism and magneto-optic effects are also discussed.      

One step towards the fabrication of a nanoscale Si-nc based laser cavity

In this paper, we report on the design of two major components of a laser architecture using Si-nc embedded in SiO₂ as the optical gain medium and sub-wavelength periodic structures to form the resonant cavity. Dimensions of the structures have been matched to near-infrared wavelengths (∼850 nm) of the maximum photoluminescent emission where optical gain has been observed from Si-nc. Both the front (FM) and rear (RM) mirrors have been fabricated by the implantation of Si ions (50 keV, 2×10¹⁷ Si⁺/cm²) through a mask, in order to produce a Bragg reflector by optical index contrast between the implanted and the non-implanted zones. Two closely spaced Bragg reflectors are used in the FM structure to allow a narrow bandpass (partial transmission) centered at 850 nm. The implanted structures have been annealed to produce Si-nc and passivation. Scanning electron microscopy (SEM) images show that the design dimensions of the structure have been obtained. Characterization of the structures by laser excitation reveals an optical gap in both mirrors between 825 and 870 nm, as per the design parameters. A quality factor Q∼95 and a reflectivity R∼0.2 have been measured for the FM. These results support the concept that a complete Si-nc based laser cavity can be built to emit coherent light.     

Ultra-broadband absorber based on cascaded nanodisk arrays

An ultra-broadband perfect absorber consisting of cascaded nanodisk arrays is demonstrated by placing insulator-metal-insulator-metal nanodisks on insulator-metal film stacks. The absorber shows over 90% absorption in a wavelength range between 600 nm and 4000 nm under transverse magnetic (TM) polarization, with an average absorptivity of 91.5% and a relative absorption bandwidth of 147.8%. The analysis of the electric field and magnetic field show that the synergy of localized surface plasmons, propagating surface plasmons, and plasmonic resonant cavity modes leads to the ultra-broadband perfect absorption, which accords well with the results of impedance-matched analysis. The influences of structural parameters and different metal materials on absorption performance are discussed. Furthermore, the absorber is polarization-independent, and the absorption remains more than 90% at a wide incident angle up to 40° under TE polarization and TM polarization. The designed ultra-broadband absorber has promising prospects in photoelectric detection and imaging.     

On the relation between plasma rotation induced by low-frequency resonant magnetic perturbations and transport in ergodic magnetic fields

The penetration of low-frequency resonant magnetic perturbations into a tokamak plasma and their influence on the plasma rotation are analyzed in linear and quaslisinear kinetic approaches. There are two explanations of experimentally observed acceleration of plasma rotation in the direction of the plasma current. First, it is a result of the resonant absorption of the momentum of the perturbation field by the plasma. Second, it is a result of a change in the radial electric field due to the ergodization of the magnetic field and the corresponding increase in the radial electron transport. It is shown that there is no contradiction between these two explanations. These are just two different interpretations of the same phenomenon. Published in Russian in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 6, pp. 420–423. The article was translated by the authors.     

Coupled mode analysis of in-plane channel drop filters with resonant mirrors

A channel drop filter system that consists of two waveguides and three cavities is studied. One cavity couples with both waveguides, while the other two work as resonant mirrors to reflect the selected channel back into the system. The operation of this configuration is analyzed, using coupled mode theory. The conditions to achieve 100% in-plane channel transfer are derived. A method to suppress the side lobes of reflection and backward drop is also proposed. The direct coupling between the cavities is not required. The analysis is verified by two-dimensional finite difference time domain simulations in 2D hexagonal photonic crystals.     

Magnetic iron oxide nanoclusters with tunable optical response

We have developed a modified synthetic protocol for the growth of monodispersed, superparamagnetic, flower-like colloidal nanoclusters (CNCs), which are consisted of smaller iron oxide nanocrystals with adjustable size. We show that their optical properties can be tuned by applying an external magnetic field. The latter controls the subtle balance of the CNCs’ mutual interactions (magnetic versus electrostatic) and drives their assembly in aqueous media. Spectrophotometric measurements reveal that a diffuse reflectance maximum, in the visible range, is related to the CNCs organization. As the strength of the external magnetic field increases, in the range 160–600 G, the spectral weight of this feature shifts towards the blue region of the spectrum. The induced photonic crystal-like response entails a remarkable magneto-optical behavior, closely associated with the size-dependent characteristics of the CNCs ensemble. Such materials pave the way for promising technological implementations in photonics.     

Polarization dependent guiding in liquid crystal filled photonic crystal fibers

A theoretical study of nematic liquid crystal filled photonic crystal fibers (LCPCFs) is presented. Detailed investigations including the polarization dependent bandgap formation and the modal properties are given for LCPCFs, in which alignment of the molecules could be controlled by external static electric field. The polarization dependent bandgap splitting caused by the high index difference between the ordinary and the extraordinary dielectric index of nematic liquid crystals provides the possibility of single-mode single-polarization guiding. A polarization operation diagram is proposed to describe the guiding behavior of LCPCFs. The influence of rotation angle ? of the director of liquid crystals on the modal properties is investigated. It is shown that the polarization axis of the guided mode is determined by the rotation angle ?, which could be controlled by external electric field.     

Large-scale ZnO inverse opal films fabricated by a sol–gel technique

We demonstrate that high-quality large-scale ZnO inverse opals can be fabricated by a simple sol–gel technique, comprising infiltration of polystyrene colloidal crystal films with zinc nitrate solution, drying and annealing at 300 C. This simple method yields continuous films, which consist of inverse opal domains (up to several hundreds of μm² in size), separated by small cracks filled with zinc oxide. Microradian X-ray diffraction was employed to verify the crystalline quality of ZnO inverse opals on the macroscale, revealing that the samples have a predominant face-centered cubic structure, and that the majority of domains have the same crystallographic orientation. The samples exhibit bright iridescence and possess photonic stop-bands in the visible to near-infrared spectrum.     

构成谐振腔的光子晶体端面反射镜的设计

研究了光子晶体作为谐振腔端面反射镜的应用.利用有效折射率法和2D PWE以及2D FDTD方法结合对构成谐振腔的两个端面反射镜进行了设计,得到左端面反射镜的最佳光子晶体晶格周期数为11×11,而右端面反射镜的最佳光子晶体晶格周期数为3×11,这为实验工作提供了良好的理论依据.