Multilayer structures with optical characteristics controlled by a magnetic field

The consideration of the gyromagnetic properties of multilayer structures with one or more magnetically active components shows that the application of a magnetic field to such structures imparts magnetically controlled optical properties to them. The effect of a magnetic field on the reflection coefficient of the multilayer structures manifests itself in two phenomena: a shift of the maximum of the spectral curve of the resonant reflection coefficient and a change (increase or decrease) in the bandwidth of this curve. The more pronounced of these two effects is the change in the bandwidth of the spectral curve of the reflection coefficient. The orientation (transverse or longitudinal) of the magnetic field applied to the multilayer structure determines important specific features of these effects. Calculation performed for two types of multilayer structures (Y₃Fe₅O₁₂?Gd₃Ga₅O₁₂ and Y₃Fe₅O₁₂?SiO₂) shows the possibility of their practical use, for example, in fiber optics.     

Subwavelength metal structures with tunable transmission characteristics by light

Extraordinary optical transmission(EOT) in subwavelength metal structures has been studied widely.Herein, we propose a strategy for tuning the EOT of the bullseye structure. Specifically, the bullseye structure was immersed in a nonlinear medium, and a controlling light was employed to change the refractive index of the medium. At different intensities and distributions of controlling light, the transmission property of signal light in the bullseye structure was simulated. The results show that a variable transmission spectrum in the bullseye structure can be realized. Moreover, the position of the central transmission peak shifts linearly with the increasing intensity of controlling light.     

Propagation and transformation of light waves in magnetically active periodic structures

The influence of an external magnetic field applied to a magnetoactive periodic structure on the specific features of formation of the photonic band gaps is established. It is shown that abrupt (stepwise) changes in the polarization of the radiation transmitted by the periodic structure and reflected from it exist near the band gap edges. The possibility of a substantial enhancement of the Faraday effect at a low level of optical losses in the magnetoactive periodic structure with a large number of periods and a dielectric contrast and without a defect layer is substantiated.     

Analytical model of light beam diffraction by one-dimensional electrically controlled non-uniform transmission photon PDLC structures

A mathematical model describing two-dimensional diffraction of quasi-monochromatic light beams by onedimensional electrically controlled non-uniform holographic photon structures in photopolymer dispersed liquid crystal (PDLC) materials is presented. The model describes light field distributions in the near and far field zones with allowance for the refractive index profile in the structure, light beam divergence, and encapsulation of liquid crystal molecules.     

Multilayer ring structures

A study of the behavior of axisymmetric structures is important for understanding the problem of the existence and stability of planet rings, spherical star constellations, and galaxies. The multilayer ring structure algorithm is developed on the basis of an exact solution to the problem of n-body gravitational axisymmetric interaction. As a result of the numerical integration of differential motion equations of point bodies composing the above structures, the evolution of several of their models is investigated. Some of them are invariable in configuration, others change forms due to interlayer interactions, and the rest throw part of bodies out of the structure.     

Finite-difference time-domain studies of light transmission through nanohole structures

We present theoretical studies on the transmission of light through subwavelength, circular apertures surrounded by circular groove structures. Finite-difference time-domain equations in cylindrical coordinates are provided for both dispersive materials and electrical conductors. The nanohole systems are composed of a circular hole in a slab, that is encircled by sinusoidal grooves defined by a period and depth. Light transmission is found to be extremely sensitive to the hole size, groove period, and groove depth. We determine a set of groove parameters that optimize transmission. Enhancements in transmission by approximately a factor of four can be achieved for silver in the visible when compared to the light incident upon the hole. These results may find utility in the design of nanoscale light manipulating devices. PACS 73.20.Mf; 78.20.Ci; 78.68.+m; 64.47.-n; 03.50.De     

Multilayer gyrotropic waveguide structures with azimuthal magnetization

An algorithm to obtain the dispersion equation and to determine the field configuration in the case of an arbitrary number of layers is developed by the successive joining of tangential components of the eigenwave electromagnetic field of a regular waveguide with concentric azimuthally magnetized gyrotropic layers. The electrical and magnetic field components in each layer are represented in the form of a linear combination of four particular analytic solutions of the system of generalized wave equations. By using an electronic computer the phase and dissipation characteristics of circular and coaxial waveguides with azimuthally magnetized ferrite-dielectric layers are computed for variations in their material and geometric parameters.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 24–28, April, 1981.     

A Ku-band magnetically insulated transmission line oscillator with overmoded slow-wave-structure

In order to enhance the power capacity, an improved Ku-band magnetically insulated transmission line oscillator(MILO) with overmoded slow-wave-structure(SWS) is proposed and investigated numerically and experimentally. The analysis of the dispersion relationship and the resonant curve of the cold test indicate that the device can operate at the near π mode of the TM01 mode, which is useful for mode selection and control. In the particle simulation, the improved Ku-band MILO generates a microwave with a power of 1.5 GW and a frequency of 12.3 GHz under an input voltage of480 k V and input current of 42 k A. Finally, experimental investigation of the improved Ku-band MILO is carried out. A high-power microwave(HPM) with an average power of 800 MW, a frequency of 12.35 GHz, and pulse width of 35 ns is generated under a diode voltage of 500 k V and beam current of 43 k A. The consistency between the experimental and simulated far-field radiation pattern confirms that the operating mode of the improved Ku-band MILO is well controlled inπ mode of the TM01 mode.     

磁绝缘传输线的有损线模型

开发了一种磁绝缘传输线(MITL)的电路模拟方法。以传输线模拟方法TLCOD为基础,将MITL分成若干段有损传输线单元,每个单元由一段无损传输线及一个对地损失电阻组成。根据磁绝缘准则判断单元的磁绝缘状况并计算相关参量,推导丝阵负载条件下MITL末端界面电压的表达式,阐述模型的求解方法及步骤;用有损线模型计算阳加速器MITL得到的结果与实验结果基本吻合,表明模型正确有效。     

A tunable magnetically insulated transmission line oscillator

A tunable magnetically insulated transmission line oscillator(MILO) is put forward and simulated. When the MILO is driven by a 430 k V, 40.6 k A electron beam, high-power microwave is generated with a peak output power of 3.0 GW and frequency of 1.51 GHz, and the relevant power conversion efficiency is 17.2%. The 3-d B tunable frequency range(the relative output power is above half of the peak output power) is 2.25–0.825 GHz when the outer radius of the slow-wave structure(SWS) vanes ranges from 77 mm to 155 mm, and the 3-d B tuning bandwidth is 92%, which is sufficient for the aim of large-scale tuning and high power output.     

磁绝缘传输线的有损线模型

 开发了一种磁绝缘传输线(MITL)的电路模拟方法。以传输线模拟方法TLCOD为基础,将MITL分成若干段有损传输线单元,每个单元由一段无损传输线及一个对地损失电阻组成。根据磁绝缘准则判断单元的磁绝缘状况并计算相关参量,推导丝阵负载条件下MITL末端界面电压的表达式,阐述模型的求解方法及步骤;用有损线模型计算阳加速器MITL得到的结果与实验结果基本吻合,表明模型正确有效。     

脉冲功率传输线传输效率的分析与计算

 基于脉冲功率系统磁绝缘传输线的时域仿真结果,分析了磁绝缘建立过程中不同阶段电极间的电子产生的能量损失特性;提出了造成能量损失的因素,包括损失的电子和磁绝缘的电子;给出了影响能量损失大小的因素,包括传输线的线长、半径比和加载脉冲的最大电压、电压的时间变化率等。通过分析不同脉冲功率波形作用下各传输阶段能量损失的起因、大小和影响因素,提出了依据极间的电子分布状态划分传输阶段,及对传输线的总效率分阶段计算的传输效率模型,给出了基于已知的传输效率数值模拟结果对不同阶段的损耗估算并最终估算传输效率的方法。     

Modeling of magnetically controlled Si-based optoelectronic devices

We present a theoretical analysis and results of modeling of a new integrated device for spintronics application, which is based on a hybrid metal–semiconductor structure. The proposed device consists of a Si-based p–i–n photodetector sandwiched between two layers of a ferromagnetic metal (3d ferromagnet or half-metallic compound). Electron–hole pairs are created in the semiconductor part of the structure by light illumination. The photocurrent flowing in such a system is shown to depend on its magnetic configuration. This is due to a difference in the specular reflection (as well as in the diffuse scattering) of spin-up and spin-down electrons and holes from magnetically polarized layers—similar to giant magnetoresistance effect in magnetic multilayers. This, in turn, allows controlling the device performance by an externally applied magnetic field. We have estimated magnitude of the effect and also determined the role of relevant material parameters.     

脉冲功率传输线传输效率的分析与计算

基于脉冲功率系统磁绝缘传输线的时域仿真结果,分析了磁绝缘建立过程中不同阶段电极间的电子产生的能量损失特性;提出了造成能量损失的因素,包括损失的电子和磁绝缘的电子;给出了影响能量损失大小的因素,包括传输线的线长、半径比和加载脉冲的最大电压、电压的时间变化率等。通过分析不同脉冲功率波形作用下各传输阶段能量损失的起因、大小和影响因素,提出了依据极间的电子分布状态划分传输阶段,及对传输线的总效率分阶段计算的传输效率模型,给出了基于已知的传输效率数值模拟结果对不同阶段的损耗估算并最终估算传输效率的方法。     

Photoelectric properties of magnetically sensitive MOS structures

The photoelectric properties of MOS structures having compensation regions near the field electrode have been studied experimentally. It is shown that the presence of such regions can lead to the appearance of a number of features in the integrated photoelectric properties: the presence of a large photovoltage signal in enhancement, dependence of the form of the photovoltage frequency dependence on the intensity of the light flux, and distortion of the shape of the photovoltage signal in inversion. The presence of compensation regions can be established using measurements of the distribution of the photovoltage over the area of the structure and measurements of the voltage dependence of the phase of the integrated photovoltage signal. The increase or decrease of the photovoltage signal in enhancement after exposure to a weak magnetic field is due to the rearrangement of the impurity-defect structure in the near-surface layer of the semiconductor, leading to the appearance of compensated semiconductor regions near the field electrode. Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 82–87, May, 1998.     

长磁绝缘传输线动态特性

基于粒子模拟研究了长磁绝缘传输线的电压电流关系、自限制流状态和损失前沿传播速度的变化规律, 验证了稳态流假设下建立的不同磁绝缘传输线模型在描述长磁绝缘传输线工作状态时的精确程度。结果表明：Mendel模型在描述长磁绝缘传输线电压电流关系时较精确; Rescaled模型计算长磁绝缘传输线自限制流状态下的阳极电流较精确; 损失前沿在长磁绝缘传输线中的传播速度沿着能量传输方向是动态变化的, 其速度的大小与输入电压上升速率相关。     

磁绝缘线振荡器的自动优化设计

为克服全电磁粒子模拟(PIC)程序不利于优化设计的弱点,提高高功率微波器件的优化设计水平,将遗传算法与全电磁粒子模拟算法有机融合,研制出二维全电磁粒子模拟并行优化程序。据此对高功率微波源器件——两个波段的磁绝缘线振荡器(MILO):C-MILO和L-MILO进行优化设计。在输入功率不变的条件下,原C-MILO效率为10.8%,经优化后效率为15.4%;原L-MILO效率为12.6%,经优化后效率为17.7%。由此得出,两类MILO模型经优化后在输入功率基本不变的情况下输出功率和效率都有很大程度的提高,且模型几何参数合理,物理图像正确。     

Ku波段磁绝缘线振荡器的数值模拟

根据现有的慢波结构色散特性的理论分析,提出了一种Ku波段的磁绝缘线振荡器（MILO）。与常见MILO的慢波结构不同,该MILO的慢波结构通过增大扼流腔的外半径来实现扼流作用,以防止阴阳极击穿。利用3维电磁场模拟软件对Ku波段MILO的开放腔模型进行了分析,得到其谐振频率为13.536 GHz以及有载品质因数为43。同时利用2.5维全电磁粒子模拟软件对其进行数值模拟,进一步优化了MILO结构,研究了输出微波的功率效率与输入电压的关系,得到的最优工作电压为600 kV。在外加电压600 kV、束流47.4 kA的情况下,模拟得到的平均功率为3.69 GW,中心频率为13.62 GHz,功率转换效率为12.6%。     

长磁绝缘传输线动态特性

基于粒子模拟研究了长磁绝缘传输线的电压电流关系、自限制流状态和损失前沿传播速度的变化规律,验证了稳态流假设下建立的不同磁绝缘传输线模型在描述长磁绝缘传输线工作状态时的精确程度。结果表明:Mendel模型在描述长磁绝缘传输线电压电流关系时较精确;Rescaled模型计算长磁绝缘传输线自限制流状态下的阳极电流较精确;损失前沿在长磁绝缘传输线中的传播速度沿着能量传输方向是动态变化的,其速度的大小与输入电压上升速率相关。     

磁绝缘线振荡器的自动优化设计

为克服全电磁粒子模拟(PIC)程序不利于优化设计的弱点, 提高高功率微波器件的优化设计水平, 将遗传算法与全电磁粒子模拟算法有机融合, 研制出二维全电磁粒子模拟并行优化程序。据此对高功率微波源器件两个波段的磁绝缘线振荡器（MILO）：C-MILO和L-MILO进行优化设计。在输入功率不变的条件下, 原C-MILO效率为10.8%, 经优化后效率为15.4%; 原L-MILO效率为12.6%, 经优化后效率为17.7%。由此得出, 两类MILO模型经优化后在输入功率基本不变的情况下输出功率和效率都有很大程度的提高, 且模型几何参数合理, 物理图像正确。