隧穿量子点分子模型与光场相互作用系统中光场的相位特性

应用Pegg-Barnett相位理论,研究了隧穿量子点分子模型与光场相互作用系统中光场的相位特性,着重分析了光场的相位概率分布及相位涨落,并讨论了平均光子数和失谐量以及时间对相位概率分布的影响．结果发现：光场相位概率分布在零附近的概率分布最大,且涨落最小,而其它范围内概率分布小且容易振荡,适当调节平均光子数和时间,能使相位概率分布由单峰结构向对称的三峰高斯分布转化,且能调节峰值的大小．     

声子对隧穿量子点分子辐射场系统量子相位的影响

用全量子理论导出隧穿量子点分子-辐射场相互作用系统状态满足的微分方程组, 在相干态辐射场和量子点分子处于隧穿激发态及基态的初始条件下, 应用Pegg-Barnett相位理论计算和分析了辐射场的相位概率分布及相位涨落, 研究了声子-量子点分子作用对辐射场相位的影响, 并与Husimi相位分布做了比较. 结果表明, 温度显著影响光场相位概率分布的时间演化规律, 声子既可以抑制也可以增强辐射场相位扩散和涨落, 取决于量子点分子的初态. Husimi相位分布和Pegg-Barnett相位分布符合度相当高. 关键词： 量子点分子 声子 量子相位 Q函数')" href="#">Q函数     

Light Scattering Simulation and Measurement of Monodisperse Spheroids using a Phase Doppler Anemometer

Mathematical tools are provided for the computation of the scattered field produced by non-spherical particles moving through the measurement volume of a phase Doppler anemometer. The phase distribution of a spheroid with random orientation is computed by using the rigorous extended boundary condition method and the ray theory. In a phase Doppler experiment the spheroid parameters are obtained by fitting the measured phase distribution with the simulated phase distribution. The numerical simulations are supported by experimental results on monodisperse spheroids.     

Object plane detection and phase-amplitude imaging based on transport of intensity equation

By using transport of intensity equation (TIE), phase distribution of an object is retrieved from through-focus intensity images. This technique allows simple and robust phase imaging compared with an interferometric approach. However, it is hard to measure phase distribution when a dynamic object moves in the direction of an optical axis. To clear this problem, autofocusing TIE which is based on local statistics is proposed. The proposed technique achieves the detection of the object plane and the retrieval of a focused object phase distribution simultaneously. In this approach, an object plane is determined by the focusing techniques based on local statistics such as variance, gradient, and Laplacian of amplitude distribution, after phase distribution in an image sensor plane is retrieved by the TIE. The performance of these three statistics is evaluated in numerical and optical experiments, and a suitable focus value is determined for precise phase imaging.     

A new analysis for extending the measurement range of the retardation-modulated differential interference contrast (RM-DIC) microscope

While considering measurements of grating-type samples with the retardation-modulated differential interference contrast (RM-DIC) microscope, we found a problem of phase objects. The problem is that smaller measured values than the actual phase distribution are obtained when phase objects are beyond the weak phase approximation range. We analyze the image characteristics of phase objects and show that the problem is caused by the effect of an image component which is proportional to the square of the phase distribution.To overcome this disadvantage, we propose a new analysis method named self phase-correction (SPC). The SPC method corrects the phase distribution of the first order approximation under the weak phase condition and obtains the actual phase distribution of an object’s phase beyond the weak phase approximation range. We propose a two-image SPC method and a three-image SPC method for the RM-DIC microscope, and examine the suitability of these methods.We confirm that the three-image SPC method effectively overcomes the problem, and that the measurement range of the RM-DIC microscope can thus be extended to a half-wavelength phase difference.     

相位修正的耦合模理论用于计算光纤Bragg光栅法布里-珀罗腔透射谱

基于光纤Bragg光栅(FBG)反射复振幅相移对FBG法布里-珀罗腔透射谱的影响,分析了传统耦合模理论计算均匀FBG反射复振幅相移产生误差的原因.引入折射率分布初始相位参数描述FBG折射率分布纵向的微小偏移,用真实的反透射系数代替简明形式的反透射系数,对传统耦合模理论进行了修正,增加了与折射率分布初始相位参数有关而与波长无关的相位因子.在此基础上进一步对计算非均匀FBG的传输矩阵法的相位进行了修正.修正后的快速计算结果用于FBG法布里-珀罗腔透射谱的计算,可反映折射率分布初始相位参数对透射峰波长位置的影响,与Rouard 算法及实验值均有较好的一致性. 关键词： 光纤Bragg 光栅 法布里-珀罗腔 耦合模理论     

Focus evolution of Gaussian beam induced by phase plate

In this article, vector diffraction theory is employed to investigate the focusing properties of the Gaussian beam through a phase plate. The phase plate may alter the wavefront phase of an incoming beam by topological charge. Both the circular phase distribution and the annular phase distribution plates are investigated. Numerical simulations show that the focal intensity distribution depends on topological charge. With changing topological charge, focal intensity distribution may evolve into ring shape, and some novel focal spots may occur. Focal intensity distribution evolving process with integer topological charge differs considerably from that with fraction topological charge. When the concentric annular phase plate is placed in the laser path, the focal intensity distribution depends on both the inner radius and topological charge. For small inner radius of the phase plate, doughnut-shape focal pattern occurs. With increasing inner radius, the diameter of the doughnut focal pattern decreases, and doughnut shape disappears slowly in some cases.     

Optical phase distribution evaluation by using an S-transform

An experimental study of the use of an S-transform to evaluate the phase distribution from a two-dimensional fringe pattern by introducing the carrier frequencies in two spatial directions, x and y, is presented. The phase distribution is extracted from the optical fringe pattern by using an S-transform gradient and S-transform phase methods. The experimental result for the Fourier transform profilometry algorithm is compared with the results of the S-transform analysis.     

基于希尔伯特变换的干涉条纹相位解调新算法

提出了一种新的应用希尔伯特变换解调干涉条纹相位的算法,可以从单幅干涉条纹图中解调出全场相位分布.在实际应用中,常借助傅里叶变换实现希尔伯特变换算法,但是会忽略负频率成分,造成相位信息的丢失.对于相位分布非单调变化的干涉条纹,提出了一种判断函数,用来计算相位信息零频率点的分布.利用相位的零频率点分布构造了一个二元模板,使用该模板对本文提出的两次希尔伯特变换法产生的包裹相位图进行修正.对修正后的包裹相位图进行解包裹处理,可以得到连续的全场相位分布.对该方法用计算机模拟进行了验证.     

Single-shot measurement of a carrier-envelope phase by use of a time-dependent polarization pulse

We propose a method for single-shot measurement of the carrier-envelope phase of high-intensity laser pulses. The method is based on observation of the electrons' spatial distribution ionized by a time-dependent polarization pulse generated by a combination of replicas of the measuring pulse. The dependence of the electrons' angular distribution on carrier-envelope phase, pulse width, delay between two combining components, and a peak intensity is calculated. Important experimental issues such as broadening of the angular distribution, Gouy phase, difference between the two replicas, and asymmetric pulse shape are also discussed.     

弱散射体产生的菲涅耳极深区散斑场相位涡旋演化的实验研究

实验提取了弱散射体产生的菲涅耳极深区的散斑场.发现当散射距离一定时,弱散射体光场的相位分布特征随散射体的粗糙度的变化而变化;对于某一弱散射体,相位分布特征随散射距离的变化而变化;当弱散射体的粗糙度大到一定程度时,才产生相位涡旋现象;散射体表面上存在相位涡旋;弱散射体产生的相位涡旋的密度随散射屏粗糙度的增大而增大,还随散射距离的增大而增大.研究结果对于认识弱散射体的相位及相位涡旋分布特征随粗糙度和散射距离的演化具有重要意义,而且对于认识散斑场随散射距离的演化有一定的帮助.     

基于随机相位调制的数字全息相移量提取方法

提出了一种在相移数字全息中提取相移角的方法.该方法通过在相移数字全息中引入随机相位板对物光波的相位进行调制,使得物光波在全息面上的相位分布成为近似理想的随机分布,进而根据这种随机分布的统计性质对相移角进行提取.计算机模拟结果表明,该方法提取出的相移角与设定的相移角之间的相对误差小于千分之一.同时,经过对比采用随机相位板和不采用随机相位板的计算结果发现,物体衍射光波在全息面上的相位分布具有一定的相关性.     

随机高斯型相位板的束匀滑特性

 针对激光系统对光束匀滑的需求,设计了高斯型连续相位板,并对其远场特性进行了研究。分别计算了相干长度为39,30,10和3 mm的高斯相位板远场光斑分布,结果显示相位板自身相关长度是决定远场能量分布的重要因素,当相干长度大于10 mm时,由于不满足各态历经条件,远场光斑分布能量分散。当相干长度小于10 mm后,由于满足各态历经条件,远场光斑能量将接近理想的高斯分布特性。通过数值计算模拟了相干长度为3 mm的连续相位板对畸变光束进行匀滑处理的过程,演示了束匀滑处理结果。通过比较匀滑前后远场光斑的能量分布,显示了畸变光束通过连续相位板后远场光斑能量分布变化情况,通过相位板后,光斑形状明显接近理想高斯分布情况。     

耗散腔中简并Raman耦合系统中光场的相位特性

利用Pegg-Barnett相位理论,研究了耗散腔中两个A型原子与相干态光场在Raman相互作用下光场的相位特性,并讨论了光场平均光子数和腔场耗散系数对光场相位特性的影响.结果表明:当腔不存在损耗时,光场相位分布概率以π/λ作周期性振荡;且在t=nπ/λ时刻,光场和原子是退纠缠的,相位分布概率曲线在极坐标图中呈单叶型结构;但在演化周期内,由于光场与原子的相互作用相位分布概率曲线会劈裂为多叶型结构.当腔场存在损耗时,相位分布概率的叶型结构会向中心扩散最终变为一个圆,即表明在考虑腔场耗散时光场的相位最终会变为随机分布;而且腔的耗散系数越大,光场相位越快趋于随机分布.另外,随光场的平均光子数增大,光场相位分布趋于集中.光场相位涨落受到腔场耗散的影响呈现出衰减周期振荡最终达到稳定值,而且达稳定值所需时间随耗散系数的增大而缩短.     

双半透镜干涉场的研究

基于波前分析和基尔霍夫衍射积分式,导出了在会聚球面波照射下圆孔或半圆孔菲涅耳衍射场沿轴的复振幅分布,特别关注其相位分布,给出了像点两侧对称点之间的相位差公式,结果表明过像点的相位变化是连续的.进而将这些结果应用于双半透镜装置,即梅斯林干涉实验,分别两种情况(即焦距相等而物距不等和物距相等而焦距不等)给出了分别由单个半透镜产生的两个衍射场之间的相位差公式和相应的干涉强度公式.结果表明,这两个衍射场沿轴的有效相位差未必是0,亦未必是π,还可能出现锯齿型的反复变化.本研究为正确地分析双半透镜产生的两个衍射场之间的干涉场提供了一个可靠的理论途径.     

基于涡流脉冲相位热成像的金属材料裂纹检测

涡流热成像可以对金属材料表面、近表面缺陷进行快速准确的检测。采用涡流热成像与脉冲相位分析相结合的方法,针对裂纹附近相位谱的分布规律及温度场对相位谱的影响关系问题,分别对带有上表面裂纹和下表面裂纹的45#钢料进行感应加热仿真和实验分析。结果表明,相位谱分布与温度大小无关,只与温度变化趋势有关,相位谱图对不均匀加热有很好的抑制作用,可以扩大裂纹的检测范围,当频率低于12.5 Hz时能够清晰地识别裂纹。结合实验验证了仿真结论的正确性,为下一步利用相位信息实现缺陷的定量检测提供参考。     

Determination of interferometer phase distributions by use of wavelets

A new technique for directly extracting phase gradients from two-dimensional (2-D) interferometer fringe data is presented. One finds the gradients by tracking the maximum modulus of the continuous wavelet transform of the fringe data and the phase distribution that is obtained, with a small error, by integration. Problems associated with phase unwrapping are thereby avoided. The technique is compared with standard methods, and excellent agreement is found. In common with Fourier-transform methods, the technique is capable of extracting the full 2-D phase distribution from a single image.     

Helicity of adjacent phase trajectories in chaotic systems

The helicity of adjacent phase trajectories in chaotic dynamic systems may be characterized by the distribution of local angular-rotation velocities of the infinitesimal displacement vector whose evolution is determined by linearized equations of motion. This distribution is close to the distribution of local Lyapunov exponents. The simplest models show that the whirl velocity of adjacent trajectories affects the rate of mixing of dynamical variables and sensitivity of the phase trajectories to perturbations.     

基于PMD的反射镜面检测实验分析

将相位测量偏折术应用于非球面反射镜面形检测,并对实验检测结果的中高频误差进行了分析研究。计算机产生正弦性条纹图,并且显示在薄膜场效应晶体管显示屏上。摄像机通过被测反射镜观察并拍摄显示屏上的条纹图。利用相移技术和相位展开技术计算得到相位分布。以相位信息为载体对光线进行追迹,并根据反射定律得到面形梯度分布,由数值积分重建面形分布。最后使用泽尼克多项式拟合分析了其中高频误差。     

径向洛伦兹阵列光束在自由空间的传输特性

推导出有初始相位分布的径向洛伦兹阵列光束在自由空间传输的解析公式,用以研究相干合成光束在自由空间的传输特性。结果表明:在远场,具有不同相位分布的光束光强剖面成为空心形状,具有相同相位分布的光束光强剖面中心为亮斑。合成光束束宽和桶中功率与子光束束腰宽度、径向阵列的初始相位分布和半径有关。对所得结果用数值计算例做了说明。当阵列半径较大和束腰宽度较小时,具有不同相位分布和相同相位的光束束宽随传输距离的变化曲线和桶中功率都趋于一致。