单模光纤中光束偏振态的自调节

本文从等效波片的观点出发,详细介绍了等效波于片的弯曲单模光纤圈,以及由几个这样的光纤圈的组合,通过简单的扭转装置来控制单模光纤中传输光偏振态的自调节原理与技术。实验证明,采用本文设计的调节系统完全可以取代经典波片,从而实现单模光纤中传输光束偏振态的自调效果。     

基于偏振干涉滤光片的宽波带偏振方向旋转器的设计

首次提出了基于偏振干涉滤光片设计方法的宽波带偏振方向旋转器。该旋转器实现了 380 nm～ 780 nm全波长范围内的偏振方向旋转。与普通的只针对某一特定波长的半波片相比 ,该偏振旋转器特性大大超越了普通 1 /2波片 ,并且入射角在± 2 0°范围仍实现偏振方向旋转 90°的要求。将该偏振方向旋转器用作 LCD或 LCOS投影仪中的偏振转换器 ,将大大提高系统的光能利用率以及投影系统的对比度。     

无端偏振控制器实验研究

在相干光通信、半导体激光放大器及某些偏振态调制光纤传感器中要求输入光偏振态稳定。本文分析了单模光纤受外应力作用所产生的应力双折射效应，并研究了采用四个光纤挤压器组成的无端偏振控制系统。     

基于圆锥偏振装置的非相干柱对称偏振光束产生方法

偏振光束由于其应用广泛并且具有某些特殊的性质,被引起广泛的关注.因此,如何通过实验的方法产生偏振光束在实际应用中是非常必要的.现提出了一种产生非相干柱对称偏振光束的方法,用偏振膜做成的圆锥偏振装置是产生非相干柱对称偏振光束的关键部件,装置能够将入射的一束自然光经透射后直接转变为非相干柱对称偏振光束.实验结果表明,该方法...     

光纤迈克尔逊干涉仪的理论与应用分析

介绍了光纤传感器,特别是干涉式光纤传感技术的优点。给出了光纤Michelson干涉仪系统的结构。重点给出了光纤Michelson干涉仪系统中信号光与参考光干涉原理以及影响干涉光强因素的理论分析。详细阐述了单模光纤偏振控制器结构、工作原理以及其对光纤Michelson干涉仪系统传感臂偏振态的控制。最后,给出了光纤Michelson干涉仪系统的应用分析。     

基于液晶的激光偏振测量系统研究

主要研究基于液晶的激光偏振测量系统,利用液晶可变相位延迟器(LCVR)代替传统测量技术中的旋转波片,改变所加的电压值控制液晶双折射系数,对入射光的偏振状态进行精确控制.通过偏振光调制法测量斯托克斯(Stokes)参量,从而实时、准确地测量激光的偏振特性.同时,利用虚拟仪器LabVIEW软件平台实现系统的数据分析、处理、界面显示和打印输出功能的一体化.研究表明:该方法能够准确地测量光束的偏振特性,能够服务于从科研实验室到工业生产过程的各类应用领域,具有广阔的应用前景.     

POTDR分布式光纤传感器

利用偏振光时域反射技术,设计了POTDR分布式光纤传感系统.实验表明:光纤未受力时,光纤中传输光偏振态的两正交模式的强度大小相反;受力时,在施力点两正交模式产生模式耦合.实验中为了将偏振信息的两模式完全分开探测,设计了高消光比偏振分束器,消光比接近50 dB;实验中采用多次测量取平均法,提高了信噪比.     

干涉型分布式光纤传感系统抗偏振衰落性能研究

为了解决分布式光纤传感系统中常出现的偏振衰落现象,提高系统的稳定性,在分析了系统检测原理基础之上,基于单模光纤的双折射等效琼斯矩阵,建立了分布式光纤传感系统模型,明确了采用不同反射器件条件下,探测光强I与入射光偏振角度i的关系。通过试验证明系统采用旋转角为π/2的法拉第旋转镜(FRM)具有较好的抗偏振衰落特性。     

激光制导中偏振态动态检测技术研究

研究了激光制导中弹体旋转或光场时变与光速偏振态间的关系,在对偏振光信号特征参数分析的基础上,介绍了一种动态检测光偏振状态的方法,采用特定的相位延迟器及差和比的数据处理方式,可以消除测量装置与偏振光相对旋转的影响,并利用琼斯矩阵法分析了这一工作原理.研制的测量装置能实时给出偏振光的旋向和椭圆度.实验结果表明,相对旋转对偏振态测量的影响确实可以消除.     

利用光纤偏振分束器和保偏光纤的传感解调系统

提出了一种利用光纤偏振分束器(PBS)和保偏光纤(PMF)中偏振模间干涉原理实现光纤布拉格光栅波长解调的方案,以提高光纤光栅传感解调系统的解调精度和稳定性。运用矩阵光学原理建立了数学分析模型,由此给出了系统输出信号与光纤光栅布拉格波长之间的关系。通过仿真分析,研究了保偏光纤长度、输入光相对于保偏光纤主轴的偏振角度和光纤偏振分束器主轴方位对系统输出信号的影响,明确提出了提高系统灵敏度的方法。根据设计方案搭建了实验系统,并进行了实验验证。结果表明:该设计方案可行,系统的波长分辨率1pm,测量精度1pm,温度可测量范围为90℃。该系统测量精度高,其稳定性优于利用M-Z型干涉仪的解调装置。     

偏振控制器的完全扰偏算法研究

从一种偏振度测试系统的系统结构出发建立光路传输模型,在分析光纤挤压型偏振控制器的工作原理后,给出整个光路传输模型的穆勒矩阵。在此基础上,文中重点研究了偏振控制器的完全扰偏算法,并用MatLab对算法进行了仿真。仿真结果表明该算法能够实现完全扰偏并有效提高偏振度测试精度。     

A 1.8-µm multiwavelength thulium-doped fiber laser based on a hybrid interference filter

A 1.8-µm tunable multiwavelength thulium-doped fiber laser based on a hybrid filter is proposed. In the designed ring-cavity fiber laser, the filter consists of one Sagnac loop and one dual-pass Mach–Zehnder filter. In the experiment, the lasing threshold is 155?mW, and a continuously tunable and stable single-wavelength laser could be realized with a minimum tuning interval of 2.1?nm within a scope of 22.5?nm. When an 1858-nm laser is obtained, the peak power fluctuation is less than 0.83?dB within 20 minutes at room temperature. By adjusting the polarization controller, stable dual-wavelength lasers are simultaneously achieved, and the peak power shift is less than 1.24?dB within a scan time of 20 minutes at room temperature. By changing the polarization state, stable triple-wavelength lasing is obtained, and the power fluctuation is less than 1.95?nm. In the experiment, the 3-dB linewidth of the laser is less than 0.4?nm.     

Properties of Dielectric Ring Resonator and Application to Moisture Measurement

This paper presents properties of a dielectric ring resonator and its application to measurement of material moisture. Theoretical analysis has been done to select better resonant modes in the resonator with higher sensitivity and wider moisture content measurable range than the formerly often used TE₀₁₁ mode by some researchers. Experiments have also been done to verify the theoretical results. The HE₂₁₂ mode in the resonator has the highest sensitivity of 1.0 MHz frequency shift corresponding to change of 1.0% moisture content. The measurable range of moisture content is up to 12% at dry basis. The mode of HE₂₁₁ has a wide measurable range approximately between 3% and 75% and its corresponding frequency shift is 12 MHz.     

Parallel confocal microscopy using high‐order axially symmetric polarized beams

A novel scheme of parallel confocal microscopy using high‐order axially symmetric polarized beams (ASPBs) is proposed. The basic concept of ASPBs is introduced first, then the principle of the scheme is presented, finally some numerical results are shown to verify the feasibility of the scheme. Seen from the results, multiple imaging spots are obtained and the size of spots is about 70% of the spot size in the single lens microscopy, and a kind of high temporal and spatial resolution parallel confocal microscopy is achieved, which may find wide applications in the fields of 3D profile measurement and biomedical imaging. Microsc. Res. Tech. 78:302–308, 2015. © 2015 Wiley Periodicals, Inc.     

高偏振消光比铌酸锂波导调制器光路设计

设计了一种新的光路结构,用于提高LiNbO_3波导相位调制器的偏振消光比。光路特点是,在质子交换波导3dB功分器的输入端同基构造了Ti-LiNbO_3波导模式分离定向耦合的结构以实现TE导模与TM模分离,Y分支波导位置下沉以避免前向TM辐射模的窜扰。效果表现为,与保偏光纤端耦合寄生的TM辐射模得到了有效抑制,寄生的TM导模被定向疏散。1 550nm波长的BPM仿真运行表明,设计光路的偏振消光比达到87dB以上。     

基于LCP径向偏振光输出的掺镱MOPA脉冲光纤激光器

为实现光纤激光器径向偏振光的高效输出,提出并搭建了基于液晶聚合物(LCP)的纳秒脉冲掺镱(Yb)主振荡器功率放大(MOPA)系统。该系统采用空间相位转换法,利用LCP涡旋半波片将全光纤MOPA激光器输出的高峰值功率、窄线宽、线偏振、高斯形分布的纳秒脉冲信号转换为横向强度呈空心环状分布的拉盖尔-高斯光。MOPA激光器系统由窄线宽连续种子源、电光强度调制器和后续的5级YDF放大器组成,通过实验获得了20.1 W的稳定LP01模输出。而后的LCP涡旋波片用作空间模式转换器,最终获得的平均输出功率为19.5 W,脉宽为10 ns,重复频率为10 kHz,横向剖面呈规则空心环形的径向偏振光输出,模式转换效率可达97%。另外,通过PBS测量法测得径向偏振光的模式纯度约为88.5%,兼具高功率与高纯度的优势。     

A method for controlling the spins of atoms using optical near-fields

On the basis of the procedure for controlling the spins of atoms using circularly polarized evanescent light proposed by Hori et al.[(1996 ) Abstracts of the 1st Asia‐Pacific Workshop on Near‐field Optics] we discuss the influence of boundary conditions on the probability of spontaneous emission and thus on the spin polarization efficiency, which was not considered in the Hori et al. study. Using the Carniglia–Mandel mode expansion of electromagnetic fields, we derive the spontaneous emission and spin polarization probabilities of atoms near a dielectric surface, and show the atom–surface distance dependence and refractive index dependence. Numerical evaluation for the 6P_1/2–6S_1/2 transition of a Cs atom indicates an increase in the efficiency of spin polarization by 30%.     

A wideband converter of the main mode of the coaxial line into the lowest symmetric mode of a circular waveguide

Band-pass (in a 0.5- to 10.0-GHz range) characteristics of a converter based on a coaxial conical line with a cylindrical inner conductor, which excites the TM₀₁ mode of a circular waveguide, are theoretically and experimentally studied. It is shown that the upper frequency of the operating band of this converter is limited by the resonance excitation of the TM ₀₁ ^c mode in the coaxial conical line. Another version of the converter based on the coaxial conical line with a conical inner conductor, in which the conversion bandwidth of 95% TEM mode power into the TM₀₁ mode power is increased to 60%, is designed.     

Selective coupling of HE11 and TM01 modes into microfabricated fully metal-coated quartz probes

We report computational and experimental investigations on injection and transmission of light in microfabricated fully Aluminum-coated quartz probes. In particular, we show that a selective coupling of either the HE(11) or the TM(01) mode can be carried out by injecting focused linearly or radially polarized beams into the probe. Optical fields, emitted by the probe after a controlled injection, are characterized in intensity and phase with the help of an interferometric technique. With the help of near-field measurement, we finally demonstrate that a longitudinally polarized spot localized at the tip apex is actually produced when the TM(01) mode is coupled into the probe.     

Bessel beams as virtual tips for near-field optics

In the previous NFO meeting, we proposed the use of confined evanescent light beams as ‘virtual’ or ‘immaterial’ tips. Unfortunately, this technique was hindered by the need for perfectly radially polarized light beams. In this communication, we propose a simple, stable and cheap method allowing the generation of beams of any polarization and more especially of purely radially polarized light beams. We also demonstrate both theoretically and experimentally that for near‐field imaging systems polarization is a limiting factor of resolution and light confinement. Finally, we present the very first experimental results dealing with virtual tips.