Spatial quantum coherent modulation with perfect hybrid vector vortex beam based on atomic medium

The perfect hybrid vector vortex beam(PHVVB)with helical phase wavefront structure has aroused significant concern in recent years,as its beam waist does not expand with the topological charge(TC).In this work,we investigate the spatial quantum coherent modulation effect with PHVVB based on the atomic medium,and we observe the absorption characteristic of the PHVVB with different TCs under variant magnetic fields.We find that the transmission spectrum linewidth of PHVVB can be effectively maintained regardless of the TC.Still,the width of transmission peaks increases slightly as the beam size expands in hot atomic vapor.This distinctive quantum coherence phenomenon,demonstrated by the interaction of an atomic medium with a hybrid vector-structured beam,might be anticipated to open up new opportunities for quantum coherence modulation and accurate magnetic field measurement.

Tightly focused properties of a partially coherent radially polarized power-exponent-phase vortex beam

A partially coherent beam called a radially polarized multi-Gaussian Schell-model power-exponent-phase vortex beam is introduced. Both the analytical formula of the beam propagating through the high-numerical-aperture objective lens based on the vectorial diffraction theory, and the cross-spectral density matrix of the beam in the focal region are derived. Then,the tight focusing characteristics of the partially coherent radially polarized power-exponent-phase vortex beam are studied numerically, and the intensity distribution, degree of polarization and coherence of the beams in the focusing region with different topological charge, power order, beam index and coherence width are analyzed in detail. The results show that the contour of the spot becomes clearer and smoother with the increase in the beam index, and the focal fields of different structures that include the flattened beam can be obtained by changing the coherence width. In addition, by changing the topological charge and power order, the intensity can gather to a point along the ring. These unique properties will have potential applications in particle capture and manipulation, especially in the manipulation of irregular particles.

Coherence vortices of partially coherent beams in the far field

Based on the propagation law of cross-spectral density function, studied in this paper are the coherence vortices of partially coherent, quasi-monochromatic singular beams with Gaussian envelope and Schell-model correlator in the far field, where our main attention is paid to the evolution of far-field coherence vortices into intensity vortices of fully coherent beams. The results show that, although there are usually no zeros of intensity in partially coherent beams with Gaussian envelope and Schell-model correlator~ zeros of spectral degree of coherence exist. The coherence vortices of spectral degree of coherence depend on the relative coherence length, mode index and positions of pairs of points. If a point and mode index are kept fixed, the position of coherence vortices changes with the increase of the relative coherence length. For the low coherent case there is a circular phase dislocation. In the coherent limit coherence vortices become intensity vortices of fully coherent Laguerre-Gaussian beams.

Propagation properties of stochastic electromagnetic double-vortex beams in a turbulent atmosphere

Based on the extended Huygens-Fresnel principle, we study the propagation properties of stochastic electromagnetic double-vortex beams in a turbulent atmosphere. The result shows that the spreading of partially coherent double-vortex beams can be smaller than that of fully coherent ones. The degree of polarization of this kind of beam will experience change, which is dependent on the degree of polarization of the source plane, the atmospheric turbulence, topological charge, and the spatial coherence. The results may have applications in space optical communication.

Partially coherent vortex beams:Fundamentals and applications

It has been over 30 years since the concept of optical vortices was first proposed by Coullet et al.in 1989,and the field of structured beams has grown extremely.In the last two decades,partially coherent vortex beams(PCVBs)have received increasing interest in the fields of optical manipulation,optical communication,optical imaging,etc.,and great progress has been made in the area of the coherence singularities,generation methods,topological charge measurements,and promising applications of PCVBs.In this review,we firstly outline the basic concepts of PCVBs.We explicate the relationship between the coherence vortices and optical vortices,and the evolution behavior of optical vortices to coherence vortices is summarized in detail.We discuss a special form of coherence singularity,ring dislocation,mathematically and physically.The ring dislocation in the correlation functions under low coherence is dependent on the mode indices,which provide a feasible approach to measure mode indices of PCVBs.Subsequently,we summarize the various methods for measuring the topological charge of PCVBs,highlight the measurement method based on the cross-correlation function,and a physical explanation on the relation between ring dislocation and topological charge is given.After that,we review the recent advances on experimental generation of several kinds of PCVBs.Lastly,we give an overview on the potential applications of PCVBs.

Review on partially coherent vortex beams

Ever since vortex beams were proposed, they are known for owning phase singularity and carrying orbital angular momentum (OAM). In the past decades, coherent optics developed rapidly. Vortex beams have been extended from fully coherent light to partially coherent light, from scalar light to vector light, from integral topological charge (TC) to fractional TC. Partially coherent vortex beams have attracted tremendous interest due to their hidden correlation singularity and unique propagation properties (e.g., beam shaping, beam rotation and self-reconstruction). Based on the sufficient condition for devising a genuine correlation function of partially coherent beam, partially coherent vortex beams with nonconventional correlation functions (i.e., non-Gaussian correlated Schell-model functions) were introduced recently. This timely review summarizes basic concepts, theoretical models, generation and propagation of partially coherent vortex beams.

Characterization of tightly focused partially coherent radially polarized vortex beams

Tight focusing properties of partially coherent radially polarized vortex beams are studied based on vectorial Debye theory.We focus on the focal properties including the intensity and the partially coherent and polarized properties of such partially coherent vortex beams through a high numerical aperture objective. It is found that the source coherence length and the maximal numerical aperture angle have direct influence on the focal intensity,as well as coherence and polarization properties.This research is important in optical micromanipulation and beam shaping.

Generation and propagation of partially coherent vortex beams

The generation and propagation of partially coherent vortex beams have been investigated experimentally.It is found that a vortex beam with more uniform intensity distribution can be obtained by decreasing the coherence of the beam.We find that the beam shape of a completely coherent beam will keep hollow profile invariant during its propagation in free space.However,the center of the beam turns to be blurred for a partially coherent vortex beam on propagation.It is also found that the beam spreads more rapidly for the vortex beam with lower coherence,and this influence can be decreased by increasing the topological charge of the vortex beam.

部分相干多离轴涡旋矢量光束的传输特性

基于相干与偏振的统一理论,采用傅里叶变换和卷积定理的方法,研究了携带多个离轴涡旋相位的径向偏振矩形对称余弦-高斯关联结构光束的传输特性.结果表明,该光束因其独特的空间相干结构而具有自分裂特性,可以分裂成4束完全相同的子波瓣.更重要的是,多离轴涡旋相位的调制可以作用在每个子波瓣上.当相干度较大时,通过调制光束的离轴涡旋数量N_(0)和光束阶数可以在焦平面处产生具有三角形或正方形等多边形空心光强分布的光斑阵列,并且每个子波瓣上对应的偏振态呈现倒三角形或斜正方形的椭圆分布.当相干度较小时,部分相干光束的空间相干性调控占主导作用,多离轴涡旋相位的调制效果消失,每个子波瓣的光强退化成高斯形式分布,但其偏振态分布仍保持不变,与光束阶数和相干长度无关.此外,当利用障碍物遮挡住其中一个离轴涡旋相位时,光束仍具有一定的自修复能力.然而,若将其中一个离轴涡旋相位完全遮挡住,此时每个子波瓣的强度分布和偏振态分布都遭到破坏,会出现不同程度的“缺口”.

部分相干径向偏振环形艾里涡旋光束在大气湍流中的传输特性研究

为了探究部分相干径向偏振环形艾里涡旋光束在大气湍流中传输时的光强闪烁特性,利用分步相位屏法研究了其在各项异性湍流中的传输特性。结果显示:随着传输距离的增大,闪烁指数首先逐渐增大,当达到最大值后再逐渐减小。当传输距离一定时,闪烁指数随着相干长度的增大而增大。随着截断因子的减小,拓扑荷数的增大,闪烁指数减小。随着相干长度、拓扑荷数的增大,部分相干径向偏振环形艾里涡旋光束保持偏振特性的能力增强。

High-power mode-programmable orbital angular momentum beam emitter with an internally sensed optical phased array

The high-power mode-programmable orbital angular momentum(OAM)beam has attracted significant attention in a wide range of applications,such as long-distance optical communication,nonlinear frequency conversion,and beam shaping.Coherent beam combining(CBC)of an optical phased array(OPA)can offer a promising solution for both generating the high-power OAM beam and rapidly switching the OAM modes.However,achieving real-time phase noise locking and formation of desired phase structures in a high-power CBC system faces significant challenges.Here,an internal phase-sensing technique was utilized to generate the high-power OAM beam,which effectively mitigated thermal effects and eliminated the need for large optical devices.An OPA with six elements was employed for experimental demonstration.The first effective generation of over 1.5 kW mode-programmable OAM beam in a continuous-wave domain was presented.Moreover,the results demonstrated that the generated OAM beam could be modulated with multiple dimensions.The topological charge can be switched in real time from-1 to-2.Notably,this OAM beam emitter could function as an OAM beam copier by easily transforming a single OAM beam into an OAM beam array.More importantly,a comprehensive analysis was conducted on power scaling,mode switching speed,and expansion of OAM modes.Additionally,the system’s compact design enabled it to function as a packageable OAM beam emitter.Owing to the advantages of having high power and programmable modes with multiple dimension modulation in phase structures and intensity distribution,this work can pave the way for producing high-power structured light beams and advancing their applications.

衍射效应诱导涡旋光束的偏振度变化

基于惠更斯-菲涅耳衍射原理以及部分相干光的相干与偏振的统一理论,研究了衍射效应诱导部分相干涡旋光束的偏振度变化.通过理论分析与数值计算表明,部分相干涡旋光束经圆孔衍射后偏振度将发生变化,在衍射场中光束的偏振度分布情况与入射光束的相干度、入射光束的拓扑电荷数、衍射孔径的大小等因素有关.

聚焦部分相干涡旋光束作用于不同折射率瑞利粒子上的辐射力

使用聚焦部分相干高斯谢尔涡旋光束,对不同折射率的瑞利粒子的辐射力做了分析,着重研究了相关长度和束腰宽度对辐射力和俘获稳定性的影响。结果表明:相关长度和束腰宽度分别存在临界值,相干长度小于等于其临界值或束腰宽度大于等于其临界值时,可利用其俘获相对折射率大于1的微粒;而在相关长度大于其临界值或束腰宽度小于其临界值时,可利用其俘获相对折射率小于1的微粒。对俘获稳定性的分析表明,需选择适当的相关长度和束腰宽度才能稳定俘获瑞利粒子。

部分相干圆偏振涡旋光束的深聚焦

基于德拜理论,研究部分相干圆偏振涡旋光束的深聚焦特性,比较左旋和右旋部分相干圆偏振涡旋光束的不同深聚焦特性,并给出相应的物理解释.分析入射光束相干性和聚焦透镜数值孔径大小对深聚焦特性的影响.研究表明,入射光束的相干度和聚焦透镜的数值孔径大小,都会影响深聚焦焦平面的光强和相干度.通过控制各相关参数的取值,可以在聚焦场中获得有广泛实际应用的平顶光束.

部分相干双涡旋光束在湍流介质中的传输

基于广义惠更斯—菲涅耳原理,推导了部分相干双涡旋光束在湍流介质中传输时光强分布变化规律的理论公式;并在实验上用螺旋相位板和随机相位板产生了此类光束,其内外双环可各自携带不同拓扑荷数;分析比较了此光束在传输中的光强分布,讨论了不同参数对其光斑大小的影响。结果表明部分相干双涡旋光束的双环在湍流大气中是相互独立传输的,其传输特性会受到光束的拓扑荷数、空间相干度、湍流扰动强弱和传输距离的影响。

部分相干涡旋光束在湍流大气中的相干性

根据广义的惠更斯-菲涅耳原理,得到了部分相干涡旋光束在湍流大气中传输时光谱相干性的理论表达式,然后详细研究了光束在湍流介质中传输时相干性的变化规律。研究表明,部分相干涡旋光束通过湍流介质后,光束的相干性主要受到湍流扰动强弱和光束所带的拓扑电荷数多少的影响,而与光源本身的相干性无关。光源所带的拓扑电荷数越多,光束的相干性越差;湍流扰动越强,光束的相干性越好。

部分相干涡旋光束的传输特性

研究了部分相干高斯-谢尔模型光束经过整数阶螺旋形位相板之后形成的部分相干涡旋光束,着重研究这种部分相干涡旋光束的传输特性。研究结果表明,这种光束在传输中呈现出环状结构的特点;整数阶螺旋形位相板的阶数越高,环状结构的半径越大;当入射的部分相干高斯-谢尔模型光束的空间相干度降低到一定程度时,环状结构消失了。此外,还研究了入射光束的空间相干度对衍射场中的光谱相干度的影响。

贝塞尔-高斯涡旋光束相干合成研究

基于相干合成技术,提出了对特定离散空间分布的高斯光束阵列加载离散涡旋相位生成二阶贝塞尔-高斯(Bessel-Gaussian,BG)涡旋光束的方案.利用干涉法、桶中功率和相关系数对合成BG涡旋光束的拓扑荷、光束质量进行了定量评价及参数优化.结果表明:基于相干合成技术能够产生特定的目标BG涡旋光束,阵列子光束紧密排布时合成BG光束的光束质量更高.该方法的提出对于其他涡旋光束的产生或者涡旋光束功率的提高具有一定的参考意义.

相干合成涡旋光束的螺旋谱分析及应用研究

应用螺旋谱分析理论,推导了相干合成涡旋光束螺旋谱分量的位置和大小,数值分析验证了理论推导的正确性.基于上述谱分析理论,可将螺旋谱分析结果作为相干合成涡旋光束质量评价函数并指导相干合成参数优化.结果表明:随着子光束数量和束腰半径的增加、组束环半径的减少可提高目标合成拓扑荷的模式纯度,同时获得高质量涡旋光束.这与采用桶中功率等传统评价函数得到的结论具有一致性.

圆环衍射效应下涡旋光束的光强变化

为了分析拓扑电荷数以及相干性对部分相干涡旋光束的影响,利用部分相干光的统一理论和惠更斯-菲涅耳衍射原理,推导出随机电磁涡旋光束在自由空间中传播时,尤其是部分相干涡旋光束经圆环衍射后光强的计算公式,研究了部分相干涡旋光束通过圆环后的夫琅和费衍射特性。通过理论分析与数值计算表明,部分相干涡旋光束经圆环衍射后的光强分布情况与入射光的相干度、入射光束的拓扑电荷数、衍射孔径的大小等因素有关。当入射光束的拓扑电荷数越大,相干长度越长,衍射孔径越小时,衍射光束的光强分布会更加清晰,衍射效果也更加明显。