基于磁流体的一维光子晶体磁场传感器的研究

基于磁流体的折射率对外加变化磁场的敏感特性,提出将磁流体作为缺陷层引入到一维光子晶体中实现磁场传感。由于缺陷的存在,使得光子晶体的透射谱中产生缺陷峰。该传感器可通过测量磁场变化时光子晶体缺陷模波长的移动对相应的磁场进行测量。利用传输矩阵法对不同结构参数下,缺陷模波长随在外加磁场的变化进行了模拟计算,为实际磁场传感器的设计提供了理论参考。     

含双负介质一维光子晶体量子阱的透射谱研究

用传输矩阵法研究一维光子晶体(AB)m(BACAB)n(BA)m的透射谱,研究发现：在双正介质和含双负介质情况下,归一化频率1.0ω0/ω处光子晶体(BACAB)n的能带皆处于光子晶体(AB)m(BA)m的禁带中,均构成以1.0ω0/ω处为对称中心的光量子阱结构。光量子阱透射谱出现对称分布的共振透射峰,呈现明显的量子化效应,透射峰数目和位置可由n调节控制,且双正和含双负光量子阱结构的透射谱结构相同,但后者的透射峰带宽、间距比前者大。该特性可用于设计微波范围内的可调性多通道滤波器和光开关等。     

1维镜像磁光光子晶体中的缺陷模分裂

为了研究镜像磁光光子晶体在外磁场中透射谱的变化,采用44传输矩阵法进行了理论分析和模拟计算。模拟结果显示,当外磁场存在的情况下,镜像光子晶体中存在的缺陷模会受到外磁场和光子晶体层数的影响,分裂成两个模式,这两个模式分别对应于原线性偏振光中的左旋光和右旋光,且左旋光和右旋光之间的频率差会随着外加磁场的增强而增大;只有当光子晶体结构多于7层时,缺陷模才会具有较高的Q值,这时模式的分裂现象才能被清晰地观察到。结果表明,磁光光子晶体的这种可调谐性可以应用到新型的滤波器设计当中。     

Research on optical fiber magnetic field sensors based on multi-mode fiber and spherical structure

A magnetic field sensor with a magnetic fluid (MF)-coated intermodal interferometer is proposed and experimentally demonstrated. The interferometer is formed by sandwiching a segment of single mode fiber (SMF) between a segment of multi-mode fiber (MMF) and a spherical structure. It can be considered as a cascade of the traditional SMF-MMF-SMF structure and MMF-SMF-sphere structure. The transmission spectral characteristics change with the variation of applied magnetic field. The experimental results exhibit that the magnetic field sensitivities for wavelength and transmission loss are 0.047 nm/mT and 0.215 dB/mT for the interference dip around 1 535.36 nm. For the interference dip around 1548.41nm, the sensitivities are 0.077 nm/mT and 0.243 dB/mT. Simultaneous measurement can be realized according to the different spectral responses.     

具有奇数通道滤波功能的光子晶体量子阱结构研究

选择适当的结构参数,用传输矩阵法计算模拟光子晶体(AB)m(CD)n(BA)m模型的透射谱,在归一化中心频率1.0（ωa/2πc）处,当光子晶体(CD)n的导带处于光子晶体(AB)m(BA)m的禁带中,且两者均以中心频率处为对称中心时,构成镜像对称的光子晶体量子阱结构。在光量子阱透射谱的中心频率处及对称的两侧,分布着具有规律的奇数局域共振峰,出现明显的量子化效应,透过峰数目和位置都可以通过光子晶体(CD)n的重复周期数n来调节,这一现象可用于设计可调性奇数通道滤波器。     

掺杂缺陷层的异质双周期光子晶体的磁光效应

通过在掺杂缺陷层的异质双周期光子晶体的表面添加一层具有Voigt效应的磁光半导体层,使该光子晶体结构的缺陷模透过率对外磁场产生响应。首先研究磁光半导体层的介电常数（折射率）随外磁场的变化规律,进而利用传输矩阵法研究该结构缺陷模的透射率随外磁场的变化规律。研究结果表明:在选取合适的材料参数和结构参数条件下,可实现缺陷模透射率与磁场的相关性,获得受磁场调控的缺陷模透射率,从而该结构可以应用于窄带滤波器的磁控开关。     

用转移矩阵法研究无序对二维光子晶体透射谱的影响

将转移矩阵法(Transfer Matrix Method)用于数值模拟无序情况下的二维光子晶体传输特性.充分利用Fortran语言中的RAND函数分别研究了晶格结构无序、圆柱半径无序、柱体形状无序、介电常数无序对光子晶体传输特性的影响.计算了多种因素无序情况下的二维正方晶格光子晶体的传输函数随频率的变化关系.计算结果表明弱无序时柱体形状影响最大,最小是圆柱半径无序.这说明在一定的无序范围里,可以认为光子晶体的传输特性能够被很好地保持.在强无序时存在共同的现象就是在低频即长波段出现光子局域化现象,无序会影响二维光子晶体的带隙宽度、位置,在强无序时会出现多个共振模.     

液晶红外磁控双折射效应的研究

利用JG-3型连续可调谐磁场仪搭建实验装置，红外1350nm激光器做光源，测量了偏振光通过磁场作用下BL-009型向列相液晶的透射光强度和旋转角度，详细分析了磁场对液晶透射比和液晶旋光性能的影响，对实验结果进行了理论分析，得出了液晶透射比和旋光角随磁场方向变化的结论。同时，通过实验测试。对液晶的阈值磁场强度进行了讨论。     

基于二维有序分立胶体晶体模板制备的金属薄膜透射谱的研究

We studied the infrared transmission properties of gold films on ordered two-dimensional nonclose- packed polystyrene （PS） colloidal crystal. The gold films consist of gold half-shells on the PS spheres and gold film with 2D arrays of holes on the glass substrate. An extraordinary optical transmission phenomenon could be found in such a structure. Simulations with the finite-difference time-domain method were also employed to get the transmission spectra and electric field distribution. The transmission response of the samples can be adjusted by controlling the thickness of the gold films. Angle-resolved measurements were performed using polarized light to obtain more information about the surface plasmon polariton resonances of the gold films. As the angle changes, the transmission spectra change a lot. The transmission spectra of p-polarized light have quite different properties compared to those of s-polarized light.     

Phase mismatching slope optimization for magneto-optic pulse compression

The collinear diffraction effects of linearly chirped Gaussian optical pulses with continuous magneto-static surface waves (MSSWs) excited in magneto-optic (MO) film waveguides under a horizontal bias magnetic field are theoretically studied. MO pulse coupling equations and the analytic solution are presented. It is shown that optical pulse compression based on MO Bragg diffraction is dependent on phase mismatching slope, which can be greatly increased by using different mode-number of incident and diffracted guided optical waves (GOWs) and appropriately choosing normalized thickness of MO film (ratio of the film thickness to the light wavelength). In TE₀ → TM₈ diffraction full-width-at-half-maximum (FWHM) ratio of the diffracted and incident optical pulses comes up to 38%.     

Analysis on characteristics of 1-D apodized and chirped photonic crystals containing negative refractive materials

Using transfer matrix method, the optical transmission properties of 1-D photonic crystals composed partially of negative refraction media are analyzed. The transmission spectra of periodic photonic crystal, chirped photonic crystal and apodized photonic crystal are numerically simulated respectively. By contrast with optical transmission properties of ordinary photo- nic crystals made of positive refraction media, the transmission spectra of apodized photonic crystal become unregular, the Bragg flat-headed area recurs but the peak of transmission does not change significantly. Futhermore, the band gap range of chirped photonic crystal diminishes gradually.     

Magnetically Controlled Millimeter Waveband Filter Based on Disk Resonator Chain

Numerical calculation of transmission spectra of the chain of disk resonators has been executed by FDTD method. Two dielectric and the semiconductor disk resonators form the chain of disk resonators. The tensor constitutive parameters of semiconductor resonator can be varied with magnetic field. The optimal range of magnetic field, providing the most effective tuning the resonance frequency of the resonators chain, is defined. The numerical values of the tuning the frequency-selective parameters of structure under study are obtained.     

含正负介质光子晶体在角度入射情况下的带隙结构变化

采用传输矩阵法研究了在角度入射情况下由PIM/NIM组成的一维光子晶体的透射谱,得到其带隙结构的变化规律:光子晶体的带隙结构会随着入射角的改变而改变,尤其对于色散的NIM与PIM组成的一维光子晶体,在nN≈0附近会产生一个新的带隙,新带隙的中心位置保持不变,但宽度会随着入射角的增大而变宽;第一级Bragg隙的中心位置和隙宽也随着入射角的变化而变化,这为二次谐波效应实现完全相位匹配创造了条件.     

空芯光子晶体光纤光子带隙的测量

首先介绍了全矢量平面波法(FVPWM),重点分析和计算了二维三角排布的光子晶体平面内传播的带隙结构图,运用数值模拟出了对应的被测空芯光子晶体光纤(HC-PCF)平面内的带隙结构图.通过实验测量了HC-PCF以及石英棒的透射谱,根据数值计算得出了HC-PCF的相对透射谱.将实验计算得到的结果与理论模拟的结果进行了对比,发现两者在相近的归一化频率处有带隙,存在一致性.     

Optimal two-vector combination-based model predictive current control with compensation for PMSM drives

The duty-ratio-based model predictive control (D-MPC) is rapidly researched for permanent-magnet synchronous machine (PMSM) drives. Existing D-MPC methods produce large current ripple and distortion. To solve this issue and promote the system performance, an optimal two-vector combination MPC (OTC-MPC) is proposed for current control in this paper. The collection of the combination is firstly produced for the proposed OTC-MPC by combining the two vectors and corresponding duty-ratio, and then the optimal combination is selected among all feasible two-vector combinations, thus, the output vectors and duty-ratio are simultaneously optimised. The optimising process is simplified so that the proposed OTC-MPC can be easily implemented. Moreover, a simplified repetitive control with feed-forward compensation method is added to eliminate the predictive current errors of MPC, and also to improve the system robustness against external disturbances. Theoretical analysis, simulation and experimental results demonstrate that the proposed OTC-MPC effectively reduces current ripple and distortion while retaining fast dynamic response compared with the conventional D-MPC.     

一维光子晶体的应变测量

采用ZnSe和Na3AlF6两种经典介质材料构造一维光子晶体,缺陷层介质为Na3AlF6。利用传输矩阵法对带有缺陷的一维光子晶体的传光特性进行了理论分析,并得到其带隙特性。分别数值研究了参考光子晶体以及应变前后测量光子晶体的透射谱,分析结果表明光子晶体所受的纵向应变与其缺陷峰波长之间呈线性关系,根据这种对应关系提出了一种新的测量应变的方法。由于粘贴光子晶体的基底与光子晶体的线膨胀系数不同,且温度变化也会引起构成光子晶体材料折射率的变化,导致光子晶体透射谱缺陷峰波长的漂移。为了消除温度误差,在测量光路中设置了与测量光子晶体结构相同的参考光子晶体,对温度的影响进行了补偿。实验表明,测量系统的灵敏度为6×10-4nm/με,测量范围为0～2000με。     

椭圆偏振光在各向异性1维光子晶体中的传输

为了解决利用传统传输矩阵法计算在各向异性材料结构中任意极化态电磁波传播遇到的困难,设计含磁光材料缺陷层的1维光子晶体。通过把入射电磁波按左旋圆偏振和右旋圆偏振进行正交分解的方法,推导出适合各向异性材料和任意极化态入射电磁波的传输矩阵算法。结果表明,该算法可以确定1维层状结构透射波和反射波偏振态的变化。     

Influence of two-dimensional magnetic photonic quantum wells on resonant tunneling spectral character

The non-magnetic material closed photonic quantum well (PQW) and magnetic material PQW structures based on the non-magnetic material open PQW are proposed. The transmission spectra and the field distributions of these three PQW structures are calculated by finite-difference time-domain method, the quantized energy states are researched, and the feasibility of enhancing spectral intensity significantly by selfstructure is disclosed. It is found that the optical transmittance of the magnetic PQW is close to 1, and the energy loss is less compared to non-magnetic PQW.Compared with the closed PQW structures, the device's volume can be reduced, the degree of free regulation of the energy band project can be increased, and more photon bound states can be obtained. The results show that the open PQW is the traveling wave well, and its capability of capturing photons is weak. However, the closed PQW and the magnetic PQW are standing wavewells. Their capabilities for capturing photons are strong,while the light field gradient of the material PQW is bigger.     

磁回旋材料柱结构光子晶体平板的单向边界模式

研究了在外加恒定磁场下,旋磁材料柱按蜂窝状晶格排列的光子晶体平板的边界所支持的电磁表面波模式。研究首先表明,在光子晶体平板的光子能带结构中,最低二条能量曲线原有的简并点,可以用外加磁场来解除,从而在这二个能带之间形成一个禁带。进一步的研究表明,基于这个光子禁带,光子晶体板平板边界所支持的表面波模式只能单方向传播,归因于系统的时间反演对称性被外磁场所破坏。这个三维系统中的单向边界模式,在平板的法向方向上,是依赖于等效全反射效应而被约束的。     

用一维矩形受限光子晶体实现单模传输

利用传输矩阵法研究了一维矩形受限光子晶体的反射谱。详细分析了TE和TM波各模式的光子禁带随矩形尺寸的变化规律。提出可以用矩形受限光子晶体实现电磁波最高模式的单模传输,尺寸越小越容易实现单模传输,其中X=1,Y=1的尺寸是最佳的结构。