光纤出射光强分布研究

对多模光纤出射光束的光强分布用横向位移法进行了理论分析和实验研究,并用数值计算的方法分析实验测量数据.结果表明,高斯光束可以很好地描述光纤出射光强的分布,光纤出射光束光强分布参数主要与光纤芯径和出纤光功率等有关,为强度调制型光纤传感器的优化研制提供了必要的实验依据.     

反射式横向位移光纤传感器特性

在实验测量的基础上形成了一种在高斯光束几何反射模型下的一维数值计算方法,可以在计算机上对反射式横向位移光纤传感器的特性进行计算分析,为该传感器的优化设计提供了一个必要工具.对用62.5/125多模光纤组成的并列反射式横向位移光纤传感器的计算分析结果表明:接收光纤端面处的反射光斑半径在180 μm附近时有最大的接收光强和最佳信噪比;反射光斑半径在180 μm～600 μm时接收光强对反射条边缘的横向位移或横向振动的动态范围、线性关系和信噪比都较佳;接收光强对反射条横向位移的分布宽度主要取决于反射条的宽度和接收光纤的芯径.     

基于无源耦合技术的高速并行光接收模块的设计与实现

提出了一种实现高速并行光接收模块中光电探测器(PD)列阵与光纤列阵精密无源耦合对准的方法,设计并制作了用于这种光学精密对准的所有组件,并用此耦合对准方法完成了PD阵列与光纤阵列之间的光耦合,制作出了12信道并行光接收模块.耦合完成的PD列阵与光纤列阵的对准误差小于1μm,从光纤列阵耦合进入PD列阵的光功率耦合效率大于8...     

高斯光束到光纤的单透镜耦合

分析了基模高斯激光束到单模和多模光纤的单透镜耦合过程中的各种损耗,把多模光纤的光场用高斯分布近似,采用模场耦合理论计算了基模高斯光束到单模和多模光纤的单透镜耦合效率.模拟计算了当激光-光纤耦合系统的工程参数(光束束宽、光纤数值孔径和光纤的纤芯芯径)一定时,单透镜耦合效率与所选用透镜的焦距之间的关系.并利用532mn激光(M2≤1.05)在几种不同焦距的透镜下对纤芯直径为3.μm的单模光纤和25μm的多模光纤进行了耦合效率的测定实验,得到了与理论计算基本吻合的实验结果.     

一种实现空间光-单模光纤的自动耦合方法

精确定位耦合光斑在光纤端面上的位置是空间光与单模光纤耦合技术的关键.提出由压电陶瓷、控制器、驱动器、光电探测器、耦合透镜及反射镜组成闭环控制系统,使用光栅式扫描初步确定最佳耦合位置后再用五点跟踪法结合一维平动精确定位实现自动耦合.推导出扫描所需步长和时间,详细阐述了光栅式扫描和五点跟踪法原理.实验结果表明,该方法可以在较短时间内根据耦合入光纤的光功率大小自动搜寻到最佳位置,获得59.2%的最大耦合效率,能校正由地表震动、气流扰动等低频干扰造成的数值偏差保持较高的耦合效率.     

60瓦半导体激光器光纤耦合器件

应用光纤列阵耦合方式，对大功率半导体激光器线列阵输出光束的快轴方向用一根柱透镜准直，准直后的光束耦合到光纤列阵中，实现出纤功率为60瓦的大功率半导体激光二极管线列阵光纤耦合器件，耦合效率大于80％，光纤的数值孔径NA为0．11。     

用于光纤多普勒测振的远距离光纤准直系统

为了解决光纤多普勒测振仪远距离非接触测量物体振动时,信号偏弱、过零点波形凌乱、难于解调的问题,本文提出了一种新型光纤准直系统。本系统主要采用在小型C-lens光纤准直器后端增加整形系统并借助ZEMAX软件对高斯光束进行准直并优化,通过对光纤准直系统成品进行耦合测试实验,使用C-lens准直器与光纤准直系统进行信号耦合效率的测试对比。实验结果表明：改进后的准直系统能够满足2 m的工作距离,空间返回光耦合效率最大能达到6.3%,极大地提升了多普勒信号的对比度,提高了远距离光纤多普勒测振仪对振动的测量精度。

     

LDA光纤耦合高效率高亮度激光输出研究

为了获得LDA(激光二级管阵列)光纤耦合高效率高亮度激光输出,光纤的芯径要尽可能小,并且耦合光束的光参数积必须小于耦合光纤的光参数积,因此必须对耦合光束进行整形。通过比较,选用反射整形法将慢轴的光参数积压缩到了原来的1/4。将LDA光束与芯径400靘,数值孔径0.37的光纤进行耦合试验,得到的耦合效率约为48%,亮度达到108量级。     

平面镜半导体光束整形的设计优化与光纤耦合

本文在光纤耦合理论分析的基础上,采用平面镜反射整形方法对半导体准直光束进行重排,提出了应用于半导体光束整形的整形器结构表达式.针对慢轴发散角较大引起整形次数增加和多次反射易损耗的特点,分析并优化平面镜的结构参数,设计了整形次数为13次的平面整形器,使得半导体激光器快、慢轴方向的光束实现光参数积均衡.通过对整个光学系统的模拟和实验,表明采用该方法能够实现条阵半导体激光耦合进入芯径200μm、数值孔径为0.22的光纤中,耦合效率接近50%.     

掺杂分布对多模光纤放大器输出特性的影响

针对高功率多模光纤放大器中稀土离子掺杂分布和形状对系统输出特性的影响,本文进行了数学模拟和理论分析.根据多模掺杂光纤速率方程考虑了种子光端面激励特性,并对纤芯模式耦合系数矩阵进行了修正,建立了多模光纤放大器理论模型.通过对功率传输方程组的求解,数值模拟了不同激励条件下6种均匀和抛物线形掺杂的双包层掺Yb3+光纤接入放大器的输出特性.计算结果证明:不同激励条件下,掺杂离子分布对输出特性的影响存在差异;通过设计光纤内掺杂离子分布规律和形状能有效抑制放大器中的高阶模式,提高输出光的光束质量.     

一种新型全光纤弹速测量系统的研制

研制了一种新型的利用激光光束反射原理的全光纤弹速测量系统。该系统采用了全光纤结构和光纤耦合器等无源器件,以输出光功率1mW, 工作波长1300nm的半导体激光器作为测试系统的光源,用光纤耦合器进行分光,实现了在一根光纤中同时传输光源和接受目标反射的信号光,避免了复杂的调节和准直过程。该系统结构简单、可靠性高,利用它,成功地测量了霍普金森杆发射的子弹速度,结果表明其速度测量相对不确定度小于1%。     

Optical trap detector for calibration of optical fiber powermeters: coupling efficiency

The optical trap detector is based on two, 1 cm x 1 cm silicon photodiodes and a spherical mirror contained in a package that is highly efficient for measuring light diverging from the end of an optical fiber. The mathematical derivation of the coupling efficiency relies on the integral directional response weighted by the angular intensity distribution of an idealized parabolic optical beam. Results of directional-uniformity measurements, acquired with the aid of a six-axis industrial robotic arm, indicate that the trap has a collection efficiency greater than 99.9% for a fiber numerical aperture of 0.24. Spatial uniformity measurements indicate that the variation of detector response as a function of position is less than 0.1%. The detector's absolute responsivity at 672.3, 851.7, and 986.1 nm is also documented by comparison with other optical detectors and various input conditions and indicates that the design is well suited for laser and optical fiber power measurements.     

扩束光纤与宽波导光栅的光耦合特性

为了研究光纤与宽波导光栅的有效耦合,基于高斯光束与波导光栅的光耦合理论,以30μm宽波导光栅为研究对象,利用矩阵光学和高斯光束理论分析和设计了一种扩束光纤,并通过分析其耦合损耗,建立了扩束光纤与波导光栅耦合模型.优化所设计扩束光纤的结构参数后,得到束腰半径为10.8μm的输出光束.最后分析了扩束光纤的结构容差,并讨论了所设计扩束光纤的输出光束、单模光纤的输出光束以及束腰半径为16 μm的自由空间高斯光束各自在光栅表面的位置变化对光栅耦合效率的影响.可知扩束光纤输出的光束与单模光纤输出的光束相比具有较大的位置容差,与束腰半径为16 μm的自由空间高斯光束相比,光耦合效率基本相同.     

Intrinsic properties of the optical coupling between axisymmetric Gaussian beams

On the basis of the overlap integral method, an approximate analytical model is derived to estimate the coupled optical power between axisymmetric Gaussian beams when transverse, axial, and angular misalignments simultaneously exist in three dimensions. Seven optical properties are derived from a detailed analysis of the model. Because the model is an approximate analytical solution to the overlap integral method, the existence of each property is also investigated by a numerical solution. Results show that all seven properties are intrinsic to the optical coupling phenomenon between Gaussian beams. Because numerous single-mode device-to-fiber coupling systems can be well described by use of Gaussian beams, the seven properties provide a solid basis to develop model-based algorithms for single-mode device-to-fiber alignment automation.     

Double Wigner distribution function of a first-order optical system with a hard-edge aperture

The effect of an apertured optical system on Wigner distribution can be expressed as a superposition integral of the input Wigner distribution function and the double Wigner distribution function of the apertured optical system. By introducing a hard aperture function into a finite sum of complex Gaussian functions, the double Wigner distribution functions of a first-order optical system with a hard aperture outside and inside it are derived. As an example of application, the analytical expressions of the Wigner distribution for a Gaussian beam passing through a spatial filtering optical system with an internal hard aperture are obtained. The analytical results are also compared with the numerical integral results, and they show that the analytical results are proper and ascendant.     

Vector wave analysis for nonnormal incident rays in epimicroscopic refractive index profile measurements

We have investigated the effects of nonnormal incident rays in calculating the refractive index profile of a dielectric sample using the reflectance measurement data obtained with a scanning confocal epimicroscope and also by solving three-dimensional vector wave equations for linearly polarized light. The numerically calculated reflection data of tightly focused Gaussian beams with different numerical apertures (NAs) on planar surfaces with various refractive indices confirm that the reflectance increases with an increase in the NA of a focusing objective lens. This is due to the nonnormal incident ray components of a Gaussian beam. We have found that the refractive index obtained with the assumption of a normal incident beam is far from the real value when the NA of a focusing lens becomes larger than 0.5, and thus the variation in the reflectance for different angular components in a Gaussian beam must be taken into consideration while using a larger NA lens. Errors in practical refractive index calculation for an optical fiber based on a normal incident beam in reflectance measurements can be as large as 1% in comparison to real values calculated by our three-dimensional vector wave equations.     

Experimental investigation of the intrinsic properties of the optical coupling between axisymmetric Gaussian beams

Continuing a previous analytical and numerical work, an experimental investigation of seven intrinsic properties of the optical coupling between axisymmetric Gaussian beams is presented. In this study, two single-mode fibers are used as the receiver and the emitter and a five-axis nanopositioning system is used to investigate optical coupling properties by moving one fiber relative to the other. Experiments demonstrate the existence of sufficiently accurate hyperbolic, parabolic, and linear trends for the optical coupling phenomenon, which can be useful for developing model-based alignment algorithms.