光谱开关与多色光场的奇点光学效应

推导出多色高斯光束和高斯-谢尔模型光束通过杨氏实验双缝传输的谱强度公式.对完全空间相干光和部分空间相干光照明杨氏实验装置出现的光谱开关作了详细研究,并判断其是否属于奇点光学效应. 结果表明：多色场奇点光学效应的判据应当是光谱开关出现时的谱强度极小值S_min=0,而不是总光强极小值I_min=0. 当用多色高斯-谢尔模型光束照明杨氏实验装置时,在近场和远场产生的光谱开关都不属于奇点光学效应. 当用多色高斯光束照明杨氏实验装置时,只有远场产 关键词： 光谱开关 奇点光学效应 完全相干和部分相干 多色光场     

部分相干厄米-高斯光束杨氏实验中的光强分布

将杨氏干涉实验作为双缝衍射现象处理,以部分相干厄米-高斯(H-G)光束为例,研究分析了多模部分相干光的杨氏双缝干涉光强和干涉条纹可见度的空间分布。数值计算说明,多模部分相干光束的空间相干参数、模阶数和缝遮拦比对衍射场中光强的空间分布(干涉花样)都有影响。当多模部分相干光的阶数为奇数时,轴上光强与光束的相干性会出现相消干涉;当多模部分相干光的阶数为偶数时,轴上光强与光束的相干性会出现相长干涉等。     

多模干涉耦合器中重叠像相干相消现象分析

根据多模干涉耦合器的自映像原理和重叠成像的规律, 首次提出多模干涉耦合器中存在重叠像相干相消现象, 推导了重叠像相干相消现象出现的条件. 在此基础上, 对对称干涉和成对干涉两种特殊重叠成像做出解释, 得出对称干涉和成对干涉成像个数及成像位置的表达式. 用实例证明了重叠像相干相消现象并不只存在于成对干涉和对称干涉两种特殊情况, 并总结了重叠像相干相消随位置数变化的规律. 用导模传输分析法验证了所得表达式和成像规律的正确性. 关键词： 集成光学 多模干涉耦合器 相干相消 导模传输分析法     

干涉型复合腔激光束相干合成中分束器的相移特性研究

分析了采用分束器构建干涉型复合腔进行激光束相干合成的过程与原理.利用分束器的特征矩阵研究了分束时产生的反射与透射相移,得到了两束相干光经过分束器分束后进行相干叠加时相移满足的普适关系,从相移的角度解释了分束器一侧发生相长干涉时另一侧必然发生相消干涉这一现象.比较了分束器与光纤耦合器在激光束相干合成应用中的一些特性,并验证了所得相移关系式的正确性.     

部分偏振部分相干光光栅衍射场的偏振特性和角相关研究

为了研究部分偏振部分相干光光栅衍射场的衍射特性.利用部分偏振部分相干光的光束相干-偏振(BCP)矩阵,推导出了部分偏振部分相干光通过任意偏振光栅后,衍射场的偏振度及场中衍射级次角相关的一般解析表达式.以部分偏振的高斯-谢尔模型光束(PGSM)为例,数值分析了偏振光栅TE和TM波的复振幅透过率、入射光束的光学参量对衍射场偏振度和场中各衍射级次的角相关的影响.计算结果表明,部分相干光透过偏振光栅后的其衍射光场是一非均匀、周期变化的部分偏振相干光场;场中对称级次的角相干值对应相等,且随衍射级次序数的增大而缓慢递减至零.     

拉盖尔-高斯模叠加而成的部分相干光的相干涡旋

对Bogatyryova等人近来提出的一种可分离位相的部分相干光的相干涡旋作了详细研究.这类新的光束由相同角向指数的拉盖尔-高斯(LG)模非相干叠加而成.研究表明，叠加LG模式的模指数，权重因子和参考点位置的选择都会影响圆刃型位错出现的位置，使得涡旋消失或出现多个相干涡旋.而且，LG模叠加而成的位相不可分离的部分相干光也存在相干涡旋. 关键词： 奇点光学 一类新的部分相干光束 相干涡旋 圆刃型位错     

部分相干涡旋光束叠加场中的合成相干涡旋及其动态传输

对由两束平行、离轴部分相干平顶涡旋光束叠加形成的合成相干涡旋做了详细研究.结果表明:合成相干涡旋的数目和位置与光束阶数、相对离轴距离、相干参数以及相对传输距离有关.在部分相干范畴内“隐藏”的合成相干涡旋对应于完全相干范畴中的合成光涡旋.并且证明在相干极限下合成相干涡旋就演化为合成光涡旋. 关键词： 相关奇点光学 合成相干涡旋 部分相干平顶光束 离轴合成     

大功率单色LED的空间相干特性

基于van Cittert-Zernike定理,从理论上计算出大功率单色发光二极管(LED)辐出光,在空间中传输后的空间相干性分布。计算结果表明,自发辐射的LED光源其辐射光在空间中传输后,由非相干光变为部分相干光,且其空间相干性与LED芯片的结构有关。实验上采用双缝干涉对LED辐射光的空间相干性进行测量,由干涉条纹的可见度与两点间的相干度之间的关系得出,非相干LED光源的辐射光在传输后为部分相干光。而采用间隔可调的双缝干涉测量两点间的相干度后发现,LED的芯片发光区域决定了其辐射光在传输中的空间相干性分布。理论计算的空间相干性分布与实验测量结果基本吻合。     

相长干涉：电磁诱导吸收

揭示修饰态原子相干对吸收的相长干涉产生电磁诱导吸收，这与修饰态原子相干对吸收的相消干涉导致电磁诱导透明的情形形成鲜明的对照. 以三个电偶极跃迁构成N型链的四能级系统为例，中间跃迁作为探测跃迁，在修饰态表象中分裂成四个相互耦合的跃迁. 这些耦合源于介质的自发辐射和介质激发态相干到基态相干的自发转移. 前者对所有四个探测跃迁产生相同符号的耦合，表现为对吸收的抑制. 而后者对其中两个跃迁产生正号的耦合，对另两个跃迁产生负号的耦合. 正是这些正负参半的耦合显著改变修饰态相干对吸收的贡献，使之由抑制吸收改变为增强吸 关键词： 电磁诱导吸收 相消干涉 相长干涉 原子相干的自发转移     

部分相干光的相干性参数简易测量方法

本文基于旋转的有机薄膜制作的相干衰减器产生部分相干光源,对杨氏双缝干涉实验进行拓展,采集部分相干光的光斑图样和干涉条纹图样,利用计算机程序处理图像,实现了对部分相干光的相干度和相干长度的快速测量。     

Phase and coherence singularities generated by the interference of partially coherent fields

A condition for the complete destructive interference of partially coherent fields emerging from pinholes in an opaque screen is derived, with the assumption of symmetry in both their geometric positions and coherence properties. We use this condition to theoretically investigate the simultaneous production of phase singularities of the optical field and of the spectral degree of coherence. We find that in cases where the number of point sources is even, a new type of mixed field/correlation singularity is observed.     

Ghost interference with partially coherent radiation

Ghost interference with partially coherent radiation sources is studied using optical coherence theory. The visibility of the ghost interference fringes is strongly influenced by the transverse size and transverse coherence width of the source. An increase of the transverse source size leads to a decrease of the fringes' visibility. An increase of the transverse coherence results in an increase of the visibility. The difference between ghost interference formed with entangled photon pairs and with partially coherent light is discussed.     

Temporally Correlated Narrowband Biphoton Interference Based on Mach–Zehnder Interferometer

Since early 1990s, Mach–Zehnder interferometer has been used to investigate the interference of biphoton wave packets. Due to subpicosecond time coherence of biphoton generated by spontaneous parametric downconversion process, some physical processes are ignored in the interferometer, most likely the biphoton time‐domain interference. Here, the two‐photon interference phenomenon based on the Mach–Zehnder interferometer is theoretically studied, where the correlated photon pairs are produced by the four‐wave mixing in atomic system. In particular, the quantum interference effect to effectively control the coherent time of two‐photon by adjusting the input delay is used. In the damped Rabi oscillation regime, two‐photon bunching and antibunching effects are observed. In addition, in the group‐delay regime, the interference between biphoton precursor, slow‐light wave packets and also in between the precursor and the slow‐light wave packets is observed, which had never been reported before. These results may have potential applications in the fields of biphoton shaping and quantum information processing.     

基于光束的相干特性拓展双缝实验教学实验内容

对部分相干光束的双缝实验干涉条纹进行了研究。利用转动的毛玻璃以及两个透镜构成了一个简单的产生部分相干光束的光学系统,通过调整毛玻璃与两个透镜的共焦点之间的距离,可以定量地控制光束的相干性。对不同相干性的光束经过双缝干涉之后的光强进行了实验观测,发现光束的相干性会对双缝干涉条纹的衬比度产生影响,光束的相干性越低,条纹衬比度也越小。并对实验结果进行了理论模拟,理论数值模拟的结果与实验观测结果基本一致。     

New effects in Young's interference experiment with partially coherent light

We analyze the coherence properties of a partially coherent optical field emerging from two pinholes in a plane opaque screen. We show that at certain pairs of points in the region of superposition the light is fully coherent, regardless of the state of coherence of the light at the pinholes. In particular, this result also holds if each pinhole is illuminated by a different laser.     

扩展光源的时间和空间相干性效应分析

在干涉仪不同支路臂中分别加入透明光学层,将扩展光源入射到迈克尔逊干涉仪,观察光场的时间和空间相干现象,发现2种情况下出射光的时间和空间相干包络极值位置发生错位现象。论证了不同支路臂中的光学层可破坏干涉场中的光波相干特性,从而导致时间和空间相干性出现超前或滞后的空间位置互易效应。利用该效应,在2个入射光源条件下,可以得到一种测量光学样品的几何厚度和折射率的实验途径,并给出了相关的计算公式。     

Measurements of the complex degree of spectral coherence by use of a wave-front-folded interferometer

A wave-front-folded interferometer composed of a K?sters prism and an image-forming lens provides a good way of measuring the complex degree of spectral coherence. Demonstrative experiments are implemented by incorporation of uncorrelated two-point spectral sources in the primary-source plane; these sources establish a spatially partially coherent wave field over the secondary source plane just in front of the interferometer. The complex degree of spectral coherence of the secondary source is successfully measured after an a priori calibration is made for the interferometer that was constructed.     

Partially coherent multiple-beam interference

The general formula for multiple-beam interference due to regular slit arrays illuminated with partially coherent quasi-monochromatic light is derived. The correlation functions chosen for partially coherent light assume Gaussian, sinc and besinc forms of correlation. The intensity distribution in the interference patterns is presented and discussed as a function of the spatial coherence condition. It is shown that spatial coherence of the illumination largely affects the features of multiple-beam interference patterns.     

Reduction of parasitic interferences in digital holographic microscopy by numerically decreased coherence length

Due to the large coherence length of laser light, optical path length (OPL) resolution in laser based digital holographic microscopy suffers from parasitic interferences caused by multiple reflections within the experimental setup. Use of partially coherent light reduces this drawback but requires precise and stable matching of object and reference arm’s OPLs and limits the spatial frequency of the interference pattern in off-axis holography. Here, we investigate if the noise properties of spectrally broadened light sources can be generated numerically. Therefore, holograms are coherently captured at different laser wavelengths and the corresponding reconstructed wave fields are numerically superimposed utilizing variable weightings. Gaussian and rectangular spectral shapes of the so synthesized field are analyzed with respect to the resulting noise level, which is quantified in OPL distributions of a reflective test target. Utilizing a Gaussian weighting, the noise level is found to be similar to the one obtained with the partially coherent light of a superluminescent diode. With a rectangular shaped synthesized spectrum, noise is reduced more efficient than with a Gaussian one. The applicability of the method in label-free cell analysis is demonstrated by quantitative phase contrast images obtained from living cancer cells.     

Complete destructive interference of partially coherent sources of acoustic waves

Theoretical analysis has recently shown that the optical fields from several point sources may exhibit complete destructive interference even if the sources are not fully coherent with respect to each other. The experimental verification of this statement in the optical domain is not easy. In this Letter we demonstrate the effect using acoustical waves instead of light waves.