Accelerating light beams along arbitrary convex trajectories

We demonstrate, theoretically and experimentally, nonbroadening optical beams propagating along any arbitrarily chosen convex trajectory in space. We present a general method to construct such beams, and demonstrate it by generating beams following polynomial and exponential trajectories. We find that all such beams, accelerating along any convex trajectory, display the same universal intensity cross section, irrespective of their acceleration. The universal features of these beams are explored using catastrophe theory.     

Interfering Bessel beams for optical micromanipulation

We examine the properties of interfering high-order Bessel beams. We implement an experimental setup that allows us to realize these interferograms, using interfering Laguerre-Gaussian beams and an axicon. We demonstrate the use of such beams for controlled rotation of microscopic particles in optical tweezers and rotators. The self-healing properties of interfering Bessel beams allow the simultaneous manipulation and rotation of particles in spatially separated sample cells.     

Generation of helical Ince-Gaussian beams with a liquid-crystal display

We generate helical Ince-Gaussian (HIG) beams by using complex amplitude and phase masks encoded onto a liquid-crystal display (LCD). These beams display an intensity pattern consisting of elliptic rings, whose number and ellipticity can be controlled, and a phase exhibiting a number of in-line vortices, each with a unitary topological charge. We show experimental results that display the properties of these elliptic dark hollow beams. We introduce a novel interference technique for generating the object and reference beams by using a single LCD and show the vortex interference patterns. We expect that these HIG beams will be useful in optical trapping applications.     

Dark and antidark diffraction-free beams

We present dark and antidark diffraction-free beams and discuss their properties. We show that all such beams must be partially spatially coherent. The new beams can be used for optical trapping of atoms.     

Quadrant detector calibration for vortex beams

This Letter reports an experimental and theoretical study of the response of a quadrant detector (QD) to an incident vortex beam, specifically a Laguerre-Gaussian (LG) beam. We have found that the LG beam response depends on the vorticity index ?. We compare LG beams with hard-ringed beams and find that at higher ? values, the QD response to LG beams can be approximated by its response to hard-ringed beams. Our findings are important in view of the increasing interest in optical vortex beams.     

Interference of traveling nondiffracting beams

We study numerically the interference resulting from the superposition of two Bessel beams propagating in free space. We discuss how to obtain such beams and show the existence of the self-imaging effect during propagation. The evolution of the superimposed Bessel beams is analyzed on the basis of the evolution of the individual beams. Our exact numerical predictions contradict previous approximated analytical treatments, showing that they can lead to quantitatively wrong results and misleading conclusions.     

Evolution of self-healing characteristic on optical Airy beam

We investigate and analyze the evolution of self-healing characteristic on diffraction-free Airy beams. We also show that different internal structure of Airy beams contribute to self-healing by breaking the integrity of Airy beams. A numerical simulation is performed and demonstrate that each independent structure undertakes different roles. It is believed that the intriguing characteristic of Airy beams can be applied in many fields such as optical tweezers, atom trapping and manipulating.     

History of accelerator neutrino beams

Neutrino beams obtained from proton accelerators were first operated in 1962. Since then, neutrino beams have been intensively used in particle physics and evolved in many different ways. We describe the characteristics of various neutrino beams, relating them to the historical development of the physics studies and discoveries. We also discuss some of the ideas still under consideration for future neutrino beams.

     

Vector Helmholtz-Gauss and vector Laplace-Gauss beams

We demonstrate the existence of vector Helmholtz-Gauss (vHzG) and vector Laplace-Gauss beams that constitute two general families of localized vector beam solutions of the Maxwell equations in the paraxial approximation. The electromagnetic components are determined starting from the scalar solutions of the two-dimensional Helmholtz and Laplace equations, respectively. Special cases of the vHzG beams are TE and TM Gaussian vector beams, nondiffracting vector Bessel beams, polarized Bessel-Gauss beams, modes in cylindrical waveguides and cavities, and scalar Helmholtz-Gauss beams. The general expression of the vHzG beams can be used straightforwardly to obtain vector Mathieu-Gauss and vector parabolic-Gauss beams, which to our knowledge have not yet been reported.     

无衍射光束的特性和生成方法

介绍了无衍射光束的概念和传输性质，描述了应用常规的光学元件和计算机产生的全息图生成无衍射光束的方法及其潜在的应用价值。     

Automatic Fourier transform and self-Fourier beams due to parabolic potential

We investigate the propagation of light beams including Hermite–Gauss, Bessel–Gauss and finite energy Airy beams in a linear medium with parabolic potential. Expectedly, the beams undergo oscillation during propagation, but quite unexpectedly they also perform automatic Fourier transform, that is, periodic change from the beam to its Fourier transform and back. In addition to oscillation, the finite-energy Airy beams exhibit periodic inversion during propagation. The oscillating period of parity-asymmetric beams is twice that of the parity-symmetric beams. Based on the propagation in parabolic potential, we introduce a class of optically-interesting beams that are self-Fourier beams—that is, the beams whose Fourier transforms are the beams themselves.     

Accelerating parabolic beams

We demonstrate the existence of accelerating parabolic beams that constitute, together with the Airy beams, the only orthogonal and complete families of solutions of the two-dimensional paraxial wave equation that exhibit the unusual ability to remain diffraction-free and freely accelerate during propagation. Since the accelerating parabolic beams, like the Airy beams, carry infinite energy, we present exact finite-energy accelerating parabolic beams that still retain their unusual features over several diffraction lengths.     

Flexible generation of optical beams with quasicrystalline structures via astigmatism induced by a tilted lens

We theoretically show that a family of optical beams with vortex-lattice structures can be reliably generated by tilting the focal lens to introduce the relative phases between the interfering beams. We also experimentally generate the quasicrystal beams to confirm the theoretical analysis. With the analytical wave functions and experimental patterns, a variety of vortex-lattice structures are manifested.     

Circular beams

A very general beam solution of the paraxial wave equation in circular cylindrical coordinates is presented. We call such a field a circular beam (CiB). The complex amplitude of the CiB is described by either the Whittaker functions or the confluent hypergeometric functions and is characterized by three parameters that are complex in the most general situation. The propagation through complex ABCD optical systems and the conditions for square integrability are studied in detail. Special cases of the CiB are the standard, elegant, and generalized Laguerre-Gauss beams; Bessel-Gauss beams; hypergeometric beams; hypergeometric-Gaussian beams; fractional-order elegant Laguerre-Gauss beams; quadratic Bessel-Gauss beams; and optical vortex beams.     

Experimental investigation of criteria for continuous variable entanglement

We generate a pair of entangled beams from the interference of two amplitude squeezed beams. The entanglement is quantified in terms of EPR paradox and inseparability criteria, with both results clearly beating the standard quantum limit. We experimentally analyze the effect of decoherence on each criterion and demonstrate qualitative differences. We also characterize the number of required and excess photons present in the entangled beams and provide contour plots of the efficacy of quantum information protocols in terms of these variables.     

平板波导中正交极化的双光束的“互陷”传输

利用变分法和数值模拟的方法研究了克尔型自聚焦介质平板波导中正交极化、中心重合的双光束的传输规律，得到了两光束做类孤子的“互陷”传输的条件，分析了在平板波导的线性双折射为零以及不能忽略的两种情况下“互陷”传输的特点.结果发现“互陷”传输的光束与严格意义的矢量空间孤子之间存在本质的不同. 关键词： 空间光孤子 矢量空间孤子 互陷传输 临界功率     

基于零级贝塞尔光束干涉产生的局域空心光束

通过对由两个零级贝塞尔光束相干叠加形成的三维衍射光场的理论分析和计算机模拟,发现当双零级贝塞尔光束的有关参量满足一定条件时,会在光轴上形成一系列高质量的局域空心光束。在此基础上,进一步分析了这种阵列局域空心光束的大小、阵列周期及局域空心光束的质量与双零级贝塞尔光束和光路参量的定量关系。推导出双零级贝塞尔光束叠加时在中心暗斑位置达到完全干涉相消的条件是通过两个环缝的能量要相同,以及产生最佳局域空心光束的内外环缝光源半径的比值为0.465。该研究为进一步设计制备基于双零级贝塞尔光束干涉实现阵列局域空心光束的新型衍射光学元件提供了理论依据和设计参量。     

EPR纠缠光束时域量子关联的实验验证

我们利用平衡零拍探测系统和数据采集系统直接测量了EPR纠缠光束信号光场与闲置光场正交分量之间的时域量子起伏,验证了其量子关联.通过对EPR纠缠光束中的一束光场进行延迟,验证了信号光与闲置光不同步时将导致量子关联减弱乃至消失.我们的实验结果为开展连续变量量子密钥分发、非高斯态的实验制备和纠缠纯化奠定了实验基础.     

Nondiffracting accelerating wave packets of Maxwell's equations

We present the nondiffracting spatially accelerating solutions of the Maxwell equations. Such beams accelerate in a circular trajectory, thus generalizing the concept of Airy beams to the full domain of the wave equation. For both TE and TM polarizations, the beams exhibit shape-preserving bending which can have subwavelength features, and the Poynting vector of the main lobe displays a turn of more than 90°. We show that these accelerating beams are self-healing, analyze their properties, and find the new class of accelerating breathers: self-bending beams of periodically oscillating shapes. Finally, we emphasize that in their scalar form, these beams are the exact solutions for nondispersive accelerating wave packets of the most common wave equation describing time-harmonic waves. As such, this work has profound implications to many linear wave systems in nature, ranging from acoustic and elastic waves to surface waves in fluids and membranes.