Coherent Vortices Properties of Partially Coherent Elegant Laguerre-Gaussian Beams in the Free Space

The analytical expression of the cross-spectral density of partially coherent elegant Laguerre-Gaussian beams propagating in free space has been derived. The coherence vortex properties of such beams have been investigated. The effect of the beam parameters, including the topological charge, radial mode index and coherence length on the coherent vortex, is analyzed. The results show that the higher order (lth) of coherent vortices split to lth first order of coherent vortex. New coherent vortices of opposite sign appear, and then pairs of coherent vortices form. The propagation distance and coherence length affect the generation of coherent vortices, while the radial mode index doesn’t affect the coherent vortices. These results might be helpful for potential application of such beams in optical communication.

Changes in Bacterial Populations in Aquatic Environment of Carassius auratus gibelio during an Outbreak of Diseases

During an outbreak of diseases caused by co-infection with both parasites and bacteria in silver crucian carp （ Carassius auratus gibelio）, aerobic anoxy- genic phototrophic （AAP） bacteria in the aquatic environment were identified by PCR using the universal primers of bacterial 16S rDNA. The bacterial populations in the ponds infected and non-infected by the diseases were measured with acridine orange direct count （AODC） method, and the data were analyzed using SPSS software. The results showed that nine dominant cuhurable bacterial species： Shewanella putrefaciens, Acinetobacter sp. , Aeromonas sp. , Proteus vulgaris, Xan- thomonas sp. , Citrobacterfieundii, Morganella morganii, Vagococcus lutrae and Providencia sp. were identified, some of which were common pathogens. The bac- terial population in infected ponds was 7. 462 x 10^6 ind./ml in July, and 1. 007 4 x 10^7 ind./ml in August, and that in non-infected ponds was 1. 460 x 10x6ind./ml in July, and 1. 911 x10^6 ind./ml in August, with significant differences between the infected and non-infected ponds. The results suggested that the outbreak of diseases in silver crucian carp was to some extent related to the bacterial population in water environment.

Economical generation of high-quality optical vortices with gradual-width Fermat spiral slit mask

A general model for creating an optical vortex using a variable-width Fermat spiral slit(FSS)mask was developed.The generated optical vortex demonstrates much better quality than those produced by slits with a uniform width.The depth of focus was nearly doubled,which can be explained by discretizing the gradual-width FSS.To demonstrate the generation robustness,the slits were printed on a transparent slide,and an output vortex beam with greater than 98%intensity purity was obtained.With the high quality and simplicity of this vortex generation method,its analysis and generation scheme are expected to be extended to generation of plasmonic vortices and short-wavelength light sources such as X-rays and electron beams.Generation of highquality optical vortex beams at an almost negligible cost will make investigation much more accessible.

Optical trapping with structured light: a review

Optical trapping describes the interaction between light and matter to manipulate micro-objects through momentum transfer.In the case of 3D trapping with a single beam,this is termed optical tweezers.Optical tweezers are a powerful and noninvasive tool for manipulating small objects,and have become indispensable in many fields,including physics,biology,soft condensed matter,among others.In the early days,optical trapping was typically accomplished with a single Gaussian beam.In recent years,we have witnessed rapid progress in the use of structured light beams with customized phase,amplitude,and polarization in optical trapping.Unusual beam properties,such as phase singularities on-axis and propagation invariant nature,have opened up novel capabilities to the study of micromanipulation in liquid,air,and vacuum.We summarize the recent advances in the field of optical trapping using structured light beams.

Measuring high orbital angular momentum of vortex beams with an improved multipoint interferometer

A multipoint interferometer(MI),uniformly distributed point-like pinholes in a circle,was proposed to measure the orbital angular momentum(OAM)of vortex beams[Phys.Rev.Lett.101,100801(2008)],which can be used for measuring OAM of light from astronomical sources.This is a simple and robust method;however,it is noted that this method is only available for low topological charge because the diffracted intensity patterns for vortex beams with higher OAM will repeat periodically.Here,we propose an improved multipoint interferometer(IMI)for measuring the OAM of an optical vortex with high topological charge.The structure of our IMI is almost the same as the MI,but the size of each pinhole is larger than a point in the MI.Such a small change enables each pinhole to get more phase information from the incident beams;accordingly,the IMI can distinguish any vortex beams with different OAM.We demonstrate its viability both theoretically and experimentally.

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.

Phyllotaxis-inspired nanosieves with multiplexed orbital angular momentum

Nanophotonic platforms such as metasurfaces,achieving arbitrary phase profiles within ultrathin thickness,emerge as miniaturized,ultracompact and kaleidoscopic optical vortex generators.However,it is often required to segment or interleave independent sub-array metasurfaces to multiplex optical vortices in a single nano-device,which in turn affects the device’s compactness and channel capacity.Here,inspired by phyllotaxis patterns in pine cones and sunflowers,we theoretically prove and experimentally report that multiple optical vortices can be produced in a single compact phyllotaxis nanosieve,both in free space and on a chip,where one meta-atom may contribute to many vortices simultaneously.The time-resolved dynamics of on-chip interference wavefronts between multiple plasmonic vortices was revealed by ultrafast time-resolved photoemission electron microscopy.Our nature-inspired optical vortex generator would facilitate various vortex-related optical applications,including structured wavefront shaping,free-space and plasmonic vortices,and high-capacity information metaphotonics.

An Eight-Step Total Synthesis of Pyrroloquinolone-Type LycopodiumAlkaloid via a Tandem Annulation Approach

Summary of main observation and conclusion A total synthesis of 6,7,9,10,12,12o-hexahydro-2-methyl-(2R/4αS,12α5)-2H,5H-benzo[e]pyrrolo-[3,2;l-ij]quinolone-4;ll(1H,3H)-dione(1),a unique pyrroloquinolone-type Lycopodium alkaloid containing a complex 6/6/6/5 tetracyclic core,has been disclosed in eight steps and 38%overall yield.The reported synthesis features a short,efficient synthesis of the crucial multi-substituted cyclohexanone intermediate with three stereogenic centers,and one-pot generation of the complex 6/6/6/5 tetracyclic core in a single tandem step.