光学系统的时间衍射积分及其应用

对含色散光学元件和其它非线性光学元件的光学系统,引入了时间ABCD矩阵元表达的时间衍射积分,用以讨论高斯光脉冲在色散介质中的传输行为,验证了线性色散系统中光传输的时间自成像,光纤中的方波自成形.     

光束变换光学的进展 第二部分：矩阵光学方法与李代数理论

在本文的这部分中,将矩阵光学方法和李代数理论用于分析非轴对称光学系统和光学列阵等对光束的变换,以及色散高斯脉冲的传输等问题。引入了一些新方法和有用的工具,如广义ABCD定律、李方法等,并举典型例说明其应用。     

矩阵理论在半导体激光器耦合中的应用

傍轴近似下的光学矩阵理论,可以简化光束传输计算过程,使光学系统设计更为方便。将ABCD变换矩阵方法引入到耦合光学系统的设计中,运用高斯光束的ABCD法则,详尽地给出了某一耦合方式下的半导体激光器耦合入单模光纤系统的设计;另一方面,对系统的耦合损耗与耦合距离的关系进行了理论计算,并把计算结果与最近的实验报道做了比较,它们基本相吻合,说明此方法是可行的、合理的。从整个设计及理论计算来看,ABCD矩阵方法减少了复杂的计算,从而简化了设计过程,与通常的衍射计算相比,它不失为一种方便、有效的方法,同时它对生产半导体激光耦合器也有实际指导意义。     

旁轴高斯光束传输性质的矩阵表示及稳定光腔和非稳定光腔模式的统一处理

本文给出对旁轴高斯光束及其传输性质的矩阵表示,把轴高斯光束情况下的ABCD定律推广到旁轴情况.本文还统一处理稳定腔和非稳定腔的模式.     

棱镜对色散补偿系统的时域ABCD矩阵分析方法

讨论了棱镜对的负色散效应,利用时域ABCD矩阵方法分析了高斯型光脉冲经棱镜对色散补偿系统的脉宽和啁啾的变化,指出输出光脉冲的脉宽是展宽还是压缩,与棱镜啁啾、棱镜间距和光脉冲在棱镜中传输的距离的取值有关.讨论了棱镜对色散补偿系统对脉冲压缩的最佳条件,指出此时输出光脉冲脉宽随棱镜啁啾的增大而骤减,且骤减程度随啁啾增大而逐渐削弱,最后趋于一稳定值.     

双棒串接Nd3+∶YAG激光器

根据测量的单根 Nd3+∶ YAG棒的热焦距 ,利用 ABCD传输矩阵计算了双棒串接的几种腔型的稳定参量 ,给出了能够满足高功率、高稳定性激光输出的稳定腔型 ,实验结果与理论分析基本相符     

啁啾脉冲堆积宽带激光非线性传输时域调制特性

为避免时域调制增长形成的高强度时间尖峰对光学元件的损坏,数值研究了啁啾堆积脉冲宽带激光非线性传输的时域调制增长规律。结果表明:对于正常色散介质,子脉冲间干涉引入的时间调制与外加调制随着传输距离的增加,不断振荡减弱;相反,对于反常色散介质,无外加时间噪声时,堆积子脉冲间的相互干涉引入的时间调制有微弱增长,但当传输距离进一步增加时,子脉冲间干涉引入的调制可以获得快速增长;而当外加非线性最快增长时间调制时,时间调制发生迅速增长,具有破坏威胁的时间尖峰易于形成。     

脉冲激光在光纤中时间波形传输特性研究

给出了光纤传输激光脉冲波形特性测试的实验光路图，对比测量了经过空气传输和光纤传输两种方式的脉冲波形。实验测试了光束耦合到不同长度的单模和多模光纤与经空气传输后的时间脉冲波形，得到了激光脉冲波形的精细结构。实验结果表明，所选的多模和单模光纤经数百米传输后的脉冲展宽在容许误差范围之内，说明所选用的光纤可以作为纳秒激光时间脉冲波形测试的理想传输介质。     

色散补偿技术中超短光脉冲传输特性的研究

本文用变分法对色散补偿技术中超短脉冲的传输特性进行了理论和数值分析.首先给出了描述超短脉冲传输特性的耦合微分方程组,然后对其进行数值求解.计算中考虑了光纤非线性系数的差异,首次引入平均非线性系数参量.分析表明,要想达到最佳的传输性能,不同的色散补偿方案,对超短脉冲的入纤能量将有不同的要求.最后给出超短脉冲最佳的入纤能量与其脉宽、色散参量比、光纤长度,以及平均色散参量间的关系图.     

脉冲在时域二次折射率介质中的传播

从空域与时域的相似性出发，把克尔介质近似为时域二次折射率介质，从而得到了脉冲在该介质中的解析形式，并给出了相应的时域传输矩阵。     

克尔介质内飞秒光脉冲时空耦合特性的光束脉冲矩阵

完整地将光脉冲的时间分量和空间分量耦合到一起,使得时间矩阵元素内有空间变量,空间矩阵元素中也有时间变量,从而推导出描述克尔介质内飞秒光脉冲时空耦合特性的光束脉冲矩阵。     

A novel ray refraction matrix for curved interface

A problem in fundamental 2 × 2 ray matrix for refraction at curved interface proposed by A. E. Siegman was found out and a novel one was derived in this paper. An experiment is introduced in detail to verify the reasonability of the novel ray matrix. Using the novel 2 × 2 ray matrix, augmented 5 × 5 ray matrix of refraction at misaligned curved interface between media of different refractive indices was deduced. With the refraction matrix, it is easy to characterize the effect of an astigmatic thick lens. The augmented ray matrix approach was applied to model and estimate the performance of an optical alignment system. Utilizing these matrices, one can readily design and evaluate optical systems, where contain astigmatic elements such as tilted spherical or cylindrical lenses, mirrors and so on. These results are also useful for cavity design, alignment, ray tracing and beam position control in 3D optical systems.     

The language of Einstein spoken by optical instruments

The mathematics of Lorentz transformations, called the Lorentz group, continues to play an important role in optical sciences. It is the basic mathematical language for coherent and squeezed states. It is noted that the six-parameter Lorentz group can be represented by two-by-two matrices. Since the beam transfer matrices in ray optics are largely based on two-by-two matrices or ABCD matrices, the Lorentz group is bound to be the basic language for ray optics, including polarization optics, interferometers, lens optics, multilayer optics, and the Poincaré sphere. Because the group of Lorentz transformations and ray optics are based on the same two-by-two matrix formalism, ray optics can perform mathematical operations that correspond to transformations in special relativity. It is shown, in particular, that one-lens optics provides a mathematical basis for unifying the internal space-time symmetries of massive and massless particles in the Lorentz-covariant world.     

Optical ray paths in a quasi-periodic waveguide or a multipass cavity with smoothly varying properties

Ray paths in a quasi-periodic optical system (waveguide of cavity) with smoothly varying properties have been constructed along the ray path. The ray-transfer matrix is constructed for a large number of ray paths; it has been shown that the conventional stability condition (the modulus of the ray-transfer matrix trace for a ray path is smaller than two) does not ensure the boundedness of the beam path after a large number of paths.     

Simulation and verification of pulsed laser beam propagation underwater using Markov chains [Invited]

One fast simulation method using Markov chains was introduced to simulate angular, energy, and temporal characteristics of pulsed laser beam propagation underwater. Angular dispersion of photons with a different number of collisions was calculated based on scattering function and the state transition matrix of Markov chains. Temporal distribution and energy on the receiving plane were obtained, respectively, by use of a novel successive layering model and receiving ratio. The validity of this method was verified by comparing it with the Monte Carlo ray tracing(MCRT) method. The simulation results were close to those obtained by MCRT but were less time consuming and had smoother curves.     

Time‐resolved X‐ray PIV technique for diagnosing opaque biofluid flow with insufficient X‐ray fluxes

X‐ray imaging is used to visualize the biofluid flow phenomena in a nondestructive manner. A technique currently used for quantitative visualization is X‐ray particle image velocimetry (PIV). Although this technique provides a high spatial resolution (less than 10 µm), significant hemodynamic parameters are difficult to obtain under actual physiological conditions because of the limited temporal resolution of the technique, which in turn is due to the relatively long exposure time (～10 ms) involved in X‐ray imaging. This study combines an image intensifier with a high‐speed camera to reduce exposure time, thereby improving temporal resolution. The image intensifier amplifies light flux by emitting secondary electrons in the micro‐channel plate. The increased incident light flux greatly reduces the exposure time (below 200 µs). The proposed X‐ray PIV system was applied to high‐speed blood flows in a tube, and the velocity field information was successfully obtained. The time‐resolved X‐ray PIV system can be employed to investigate blood flows at beamlines with insufficient X‐ray fluxes under specific physiological conditions. This method facilitates understanding of the basic hemodynamic characteristics and pathological mechanism of cardiovascular diseases.     

X‐ray analog pixel array detector for single synchrotron bunch time‐resolved imaging

Dynamic X‐ray studies can reach temporal resolutions limited by only the X‐ray pulse duration if the detector is fast enough to segregate synchrotron pulses. An analog integrating pixel array detector with in‐pixel storage and temporal resolution of around 150 ns, sufficient to isolate pulses, is presented. Analog integration minimizes count‐rate limitations and in‐pixel storage captures successive pulses. Fundamental tests of noise and linearity as well as high‐speed laser measurements are shown. The detector resolved individual bunch trains at the Cornell High Energy Synchrotron Source at levels of up to 3.7 × 10³ X‐rays per pixel per train. When applied to turn‐by‐turn X‐ray beam characterization, single‐shot intensity measurements were made with a repeatability of 0.4% and horizontal oscillations of the positron cloud were detected.     

X‐ray dynamical diffraction Fraunhofer holography

An X‐ray dynamical diffraction Fraunhofer holographic scheme is proposed. Theoretically it is shown that the reconstruction of the object image by visible light is possible. The spatial and temporal coherence requirements of the incident X‐ray beam are considered. As an example, the hologram recording as well as the reconstruction by visible light of an absolutely absorbing wire are discussed.     

General method for determining the first order gradients of skew rays of optical systems with non-coplanar optical axes

Current commercial software for the analysis and design of optical systems uses finite difference (FD) approximation methodology to estimate the gradient matrix of a ray with respect to system variables. However, FD estimates are intrinsically inaccurate and are subject to gross error when the denominator is excessively small relative to the numerator. This paper avoids these problems and determines the gradient matrix of the exit ray traveling along an optical system with a non-coplanar axis. To achieve this, the gradient matrix of the rays reflected/refracted by flat or spherical boundary surfaces are first determined by directly differentiating the skew-ray tracing equations. By introducing a Jacobian matrix, which represents the partial derivatives specifying the rates of changes between boundary variables and element variables, one can obtain the gradient matrix of the exit ray of an element with respect to its independent variables. This methodology will be useful in the analysis of rays and in design of optical systems with non-coplanar axis. A right-angle prism is used as illustrative example to validate its applications.     

自聚焦平面微透镜的成像矩阵

利用普通光线方程对自聚焦平面微透镜的成像光线进行了分析;得出了微透镜的成像矩阵,给出了自聚焦平面微透镜高斯参量的计算公式;并与实验结果进行了比较,得到了满意的结果。