Method for generating spatiotemporal coherency vortices and spatiotemporal dislocation curves.

A simple method for designing spatiotemporal coherency vortices (STCVs) and spatiotemporal dislocation curves (STDCs) is introduced by means of coherent-mode representation and Fourier transforms. A partially coherent pulsed beam is represented by an incoherent superposition of a Gaussian and a Hermite-Gaussian pulsed beam with different waist positions. It well demonstrates that there exist STCVs and STDCs in the space-time plane. The detailed numerical calculations are performed to address the dependence of waist distance of two modes, reference position, beam order, distribution of original spectrum, topological charge and mode weights ratio on the STCVs and STDCs. The physical interpretation behind numerical results is shown. A possible scheme for experimental synthesis of the STCVs is proposed. The obtained results may have potential applications in the fields of light-matter interaction, spatiotemporal spin-orbit angular momentum coupling and STCV-based optical trapping and optical manipulation.

Genome Resource of Streptomyces atratus PY-1, a Broad-Spectrum Antimicrobial Strain in Particular Antagonistic Against Plasmopara viticola.

Streptomyces atratus PY-1 exhibited promising antimicrobial properties; in particular, it is highly inhibitory to Plasmopara viticola, which causes downy mildew of grape. It is very necessary to carry out systematic and in-depth research on the PY-1 strain for the improvement, application, and promotion of biocontrol agents. The PY-1 genome was fully sequenced and assembled. We present the draft genome sequence of PY-1, with a size of 9, 254, and 781 bp. Preliminary analysis on the PY-1 genome sequence shows that at least 35 gene clusters are involved in the biosynthesis of polyketides, terpenes, and nonribosomally synthesized peptides.

Overexpression of the First Peanut-Susceptible Gene, AhS5H1 or AhS5H2, Enhanced Susceptibility to Pst DC3000 in Arabidopsis.

Salicylic acid (SA) serves as a pivotal plant hormone involved in regulating plant defense mechanisms against biotic stresses, but the extent of its biological significance in relation to peanut resistance is currently lacking. This study elucidated the involvement of salicylic acid (SA) in conferring broad-spectrum disease resistance in peanuts through the experimental approach of inoculating SA-treated leaves. In several other plants, the salicylate hydroxylase genes are the typical susceptible genes (S genes). Here, we characterized two SA hydroxylase genes (AhS5H1 and AhS5H2) as the first S genes in peanut. Recombinant AhS5H proteins catalyzed SA in vitro, and showed SA 5-ydroxylase (S5H) activity. Overexpression of AhS5H1 or AhS5H2 decreased SA content and increased 2,5-DHBA levels in Arabidopsis, suggesting that both enzymes had a similar role in planta. Moreover, overexpression of each AhS5H gene increased susceptibility to Pst DC3000. Analysis of the transcript levels of defense-related genes indicated that the expression of AhS5H genes, AhNPR1 and AhPR10 was simultaneously induced by chitin. Overexpression of each AhS5H in Arabidopsis abolished the induction of AtPR1 or AtPR2 upon chitin treatment. Eventually, AhS5H2 expression levels were highly correlated with SA content in different tissues of peanut. Hence, the expression of AhS5H1 and AhS5H2 was tissue-specific.

Complex and phase screen methods for studying arbitrary genuine Schell-model partially coherent pulses in nonlinear media.

Partially coherent pulses, especially those with non-Gaussian correlated functions, have rarely been explored in nonlinear media because of the demanding procedure of the widely used coherent-mode representation method. This study develops temporal analogues of the complex screen and phase screen methods, which were recently introduced for the spatial counterpart of a partially coherent beam. These methods were employed to study the beam propagation properties of partially coherent pulses, and the obtained results show that they both are highly precise, convenient, and powerful. We believe that these protocols can effectively provide useful insight into the behavior of many coherence-related phenomena in nonlinear media.

Universal orbital angular momentum detection scheme for any vortex beam.

Existing methods for probing the orbital angular momentum carried by vortex beams have many limitations and are generally only applicable to specific types of vortex beam. In this work, we present a concise and efficient universal method for probing the orbital angular momentum that is applicable for any type of vortex beam. The vortex beam could range from being fully to partially coherent, with different spatial modes including Gaussian vortex beam, Bessel-Gaussian beam, Laguerre-Gaussian beam, etc., of any wavelength including x rays, matter waves such as electron vortices, and with high topological charge. This protocol only requires a (commercial) angular gradient filter, making it very easy to implement. The feasibility of the proposed scheme is demonstrated both theoretically and experimentally.

Structurally stable beams in the turbulent atmosphere: dark and antidark beams on incoherent background [Invited].

We demonstrate analytically and verify numerically that recently discovered, and experimentally realized, partially coherent dark and antidark beams are structurally stable on propagation in a statistically homogeneous, isotropic random medium, such as the turbulent atmosphere. The dark/antidark beams defy diffraction in free space, and they manifest themselves as dark/bright notches/bumps against an incoherent background. The structure of a bump/notch remains invariant on propagation of the beam through the random medium, while the peak amplitude of the bump/notch decays with the propagation distance in the medium at a rate dependent on the strength of the medium turbulence. We also evaluate numerically the scintillation index of such beams and show that it is significantly lower than that of generic, low-coherence Gaussian Schell-model beams. The combination of structural stability and low scintillations makes partially coherent dark/antidark beams very promising candidates for information transfer and optical communications through atmospheric turbulence.

Flexible autofocusing properties of ring Pearcey beams by means of a cross phase.

In this Letter, we introduce a new class of angular dependent autofocusing ring Pearcey beams by imposing a cross-phase structure. Due to this structure, the beam exhibits a non-uniform abrupt autofocusing behavior. Unlike the properties of the ring Pearcey beam without a cross phase [Opt. Lett.43, 3626 (2018)OPLEDP0146-959210.1364/OL.43.003626], we can flexibly adjust the focal length of the beam and its focusing ability, as well as the direction of the ring Pearcey beams, with the help of only the cross-phase structure. Furthermore, the Poynting vectors are employed to demonstrate convincingly the beam-focusing mechanism. Such beams with these fascinating characteristics are anticipated to find potential applications in optical tweezing, three-dimensional printing, material processing, and so on.

Temporal Boundary Solitons and Extreme Superthermal Light Statistics.

We discover the formation of a temporal boundary soliton (TBS) in close proximity of a temporal boundary, moving in a nonlinear optical medium, upon high-intensity pulse collision with the boundary. We show that the emergent TBS is unstable to perturbations caused by the cross-phase modulation between the TBS and the other soliton products of the collision and that such instability triggers colossal intensity fluctuations of the reflected pulse ensemble with unprecedented magnitudes of the normalized autocorrelation function for an even weakly fluctuating input pulse.

Partially coherent radially polarized fractional vortex beam.

A new kind of partially coherent vector beam, named a partially coherent radially polarized fractional vortex (PCRPFV) beam, is introduced as a natural extension of the recently introduced scalar partially coherent fractional vortex beams [Zeng et al., Opt. Express26, 26830 (2018)10.1364/OE.26.026830]. Realizability conditions and propagation formulas for a PCRPFV beam are derived. Statistical properties of a focused PCRPFV beam, such as average intensity, degree of polarization, state of polarization and cross-spectral density matrix, are illustrated in detail and compared with that of a partially coherent radially polarized integer vortex beam and a scalar partially coherent fractional vortex beam. It is found that the statistical properties of a PCRPFV beam are qualitatively different from these simpler beam classes and are strongly determined by the vortex phase (i.e., fractional topological charge) and initial coherence width. We demonstrate experimental generation of PCRPFV beams and confirm their behavior. Our results will be useful for the rotating and trapping of particles, the detection of phase objects, and polarization lidar systems.

Vortex preserving statistical optical beams.

We establish a general form of the cross-spectral density of statistical sources that generate vortex preserving partially coherent beams on propagation through any linear ABCD optical system. We illustrate our results by introducing a class of partially coherent vortex beams with a closed form cross-spectral density at the source and demonstrating the beam vortex structure preservation on free space propagation and imaging by a thin lens. We also show the capacity of such vortex preserving beams of any state of spatial coherence to trap nanoparticles with the refractive index smaller than that of a surrounding medium.

Generation of novel partially coherent truncated Airy beams via Fourier phase processing.

We propose theoretically and numerically, for the first time, the generation of novel partially coherent truncated Airy beams (NPCTABs) with Airy-like distributions for both intensity and degree of coherence via Fourier phase processing. We demonstrate a clear link between the magnitude and frequency of intensity and degree of coherence distributions oscillations of generated beams, and the source coherence and the phase screen parameter. Thus, the source coherence and phase can serve as convenient parameters to control the intensity and degree of the coherence of NPCTABs. Furthermore, we discover that NPCTABs are more stable than the fully coherent truncated Airy beams (FCTABs) during their propagation in free space and can maintain their Airy-like profile for an extended propagation distance. The interesting and tunable characteristics of these novel beams may find applications in particle trapping, phase retrieval, and optical imaging.

Self-healing properties of Hermite-Gaussian correlated Schell-model beams.

We study theoretically and experimentally the influence of the obstacle position separation from the source on the self-healing capacity of partially coherent beams using Hermite-Gaussian correlated Schell-model beams as a case in point. We establish that the shorter the distance between the obstacle and the source plane and the longer the distance between the obstacle and the observation (receiver) plane, the better the self-healing capacity of the beams. In addition, a similarity degree between the reconstructed and original beams is introduced to quantify the self-healing capacity of partially coherent beams. The derived interesting results may find applications in optical information processing, image transmission, and recovery.

Universal self-similar asymptotic behavior of optical bump spreading in random medium atop incoherent background: reply.

In his comment [Opt. Lett.45, 3510 (2020)OPLEDP10.1364/OL.385246], Charnotskii claims that the cross-spectral densities recently studied in Opt. Lett.45, 698 (2020)OPLEDP10.1364/OL.385246 of partially coherent beams atop a statistical background do not satisfy the non-negative definiteness requirement. We argue that Charnotskii's claim stems from his misunderstanding of the non-negative definiteness concept as applied to the model of Opt. Lett.45, 698 (2020)OPLEDP10.1364/OL.385246.

Universal self-similar asymptotic behavior of optical bump spreading in random medium atop incoherent background.

We demonstrate theoretically that the average spatial intensity profile of any partially coherent optical beam, composed of a finite-power bright intensity bump atop a fluctuating background, evolves into a universal self-similar Gaussian shape upon long-term propagation in a statistically homogeneous, isotropic linear random medium. The result depends neither on the degree of the background spatial coherence nor on the strength of the medium turbulence. To our knowledge, this is the first demonstration of universal self-similar asymptotics in linear random media.

Self-steering partially coherent vector beams.

We introduce a class of self-steering partially coherent vector optical beams with the aid of a generalized complex Gaussian representation. We show that such partially coherent vector beams have mobile guiding centers of their intensity and polarization state distributions on the beam free space propagation that could be employed to generate far-field polarization arrays. Further, we introduce theoretically and realize experimentally a class of vector beams with inhomogeneous statistical and nontrivial far-field angular distributions, which we term cylindrically correlated partially coherent (CCPC) vector beams. We find that such novel beams possess, in general, cylindrically polarized, far-field patterns of an adjustable degree of polarization. The steering control of the intensity and polarization of the self-steering CCPC vector beam is also demonstrated in experiment. Our findings can find important applications, such as trapping of neutral microparticles and excitation of novel surface waves.

High-quality partially coherent Bessel beam array generation: erratum.

In this erratum, we correct mistakes in Eqs. (6), (8), and (9), typo in Eq. (11), as well as lattice period magnitudes and units in Fig. 1. We also update the funding information in Opt. Lett.43, 3188 (2018)OPLEDP0146-959210.1364/ol.43.003188.

High-quality partially coherent Bessel beam array generation.

We propose a protocol for generating high-quality, partially coherent (quasi-)Bessel beam arrays with controllable beam order and spatial distributions. Our protocol involves, apart from beam intensity shaping, coherence engineering of recently introduced optical coherence lattices. Our theoretical results are validated with the experimental realization of partially coherent Bessel beam arrays. The novel beam arrays are anticipated to be useful for multi-particle trapping and micromanipulation, optical metrology and microscopy, as well as for 3D imaging.

Vector optical coherence lattices generating controllable far-field beam profiles.

We introduce partially coherent vector sources with periodic spatial coherence properties, which we term vector optical coherence lattices (VOCLs), as an extension of recently introduced scalar OCLs. We derive the realizability conditions and propagation formulae for radially polarized VOCLs (i.e., a typical kind of VOCLs). We show that radially polarized VOCLs display nontrivial propagation properties and generate controllable intensity lattices in the far zone of the source (or in the focal plane of a lens). By adjusting source coherence, one can obtain intensity lattices with bright or dark nodes. The latter can be employed to simultaneously trap multiple particles or atoms as well as in free-space optical communications. We also report the experimental generation of radially polarized VOCLs and we characterize VOCLs propagation properties.

Experimental verification of significant reduction of turbulence-induced scintillation in a full Poincaré beam.

It is theoretically predicted in [Opt. Lett.37, 1553 (2012)] that a full Poincaré (FP) beam can significantly reduce turbulence-induced scintillation. In this paper, we propose a method for synthesizing a FP beam for different beam orders and report experimental generation of the first-, second- and third-order FP beams. Furthermore, we carry out experimental measurement of the scintillation index of a FP beam passing through thermally induced turbulence. It is demonstrated that the FP beam indeed can significantly reduce the scintillation index compared to a Gaussian beam under certain conditions. Our results will be useful in long-distance free-space optical communications.

Statistical properties of a partially coherent cylindrical vector beam in oceanic turbulence.

Propagation of a partially coherent cylindrical vector Laguerre-Gaussian (PCCVLG) beam passing through oceanic turbulence is studied with the help of the extended Huygens-Fresnel integral formula and unified theory of coherence and polarization of light. Analytical formula for the cross-spectral density matrix of a PCCVLG beam propagating in oceanic turbulence is derived, and the statistical properties, such as intensity distribution and degree of polarization, of a PCCVLG beam on propagation in oceanic turbulence are illustrated in detail. It is found that the statistical properties of a PCCVLG beam in oceanic turbulence vary as the sea-related parameters, initial coherence length, and mode orders vary, and such beam is depolarized on propagation. Our results will be useful in optical underwater communications, imaging, and sensing.