Hermite-Gaussian beams with sinusoidal vortex phase modulation

In this Letter,vortex phase and sinusoidal phase modulations of Hermite-Gaussian beams are studied theoretically and experimentally.The coding method of the experiment is introduced in detail,and the evolution law of focus under different beam order(m,n) and topological charge(l) is given.In order to verify the accuracy of the generation experiment,the optical field distribution under sinusoidal vortex modulation is analyzed deeply.The relevant analysis and methods provided in this Letter have certain practical significance for the development of laser mode analysis,optical communication,and other fields.     

Compression of digital holograms via adaptive-sparse representation

Efficient storage and transmission of digital holograms (DHs) requires the development of appropriate compression techniques for such a special class of images. In this Letter, we investigate a method to compress DHs using a sparse matrix representation. Using digital holography to numerically manage complex wave fields, we are able to apply an adaptive mask, based on a threshold filter, to the object wave field. From there, we store the result of this filtering by sparse representation. In this Letter, we demonstrate that using sparse representation allows for a high compression factor with minimal loss in the quality of the reconstructed image. This technique is efficient for storage and transmission of DHs.     

Laser-printer computer-generated holograms exhibiting suppressed higher orders in the replay field

Conventional computer-generated holograms (CGHs) consist of regularly spaced square pixels, which, when replayed, exhibit many repeated higher orders. Furthermore, such pixellated CGHs are not well suited to printing using a conventional laser printer. In this Letter a novel method is presented that exploits the characteristics of a conventional laser-printing process to generate holograms with replay fields that exhibit markedly suppressed higher orders.     

Do evanescent waves contribute to the far field?

Evanescent waves have become of considerable interest in recent years because of developments in near-field optics. Claims have been made that such waves contribute to the radiation fields of sources and to the far fields of scatterers. We show, by considering a spherical scalar wave and a linear electric dipole field, that these claims are misleading and that such contributions are without physical consequences. Our conclusions apply to a much broader class of fields than those considered in this Letter.     

On the origin of discontinuity of the hyperfine fields at Fe nuclei in bulk iron and aerosol Fe nanoparticles

Advancing the early work in which a discontinuity of hyperfine fields at ⁵⁷Fe nuclei in bulk iron and in aerosol Fe nanoparticles has been revealed by analyzing their Mössbauer spectra the present Letter evidences that the existence of several peaks in the hyperfine distribution (HFD) for bulk Fe is caused with the internal magnetic fields owing to its multidomain structure whereas aerosol Fe nanoparticles are single-domain and show only a unique peak in HFD. This argument has been corroborated by transformation of the HFD pattern for Fe foil after applying the external magnetic field of 0.03 T.     

Construction of homogeneous propagators for massive half-integer spin fields in 3+2 De Sitter space,with implications for the massless limit

In this Letter we obtain explicit expressions of homogeneous propagators for half-integer spin fields and their flat-space limits, showing that propagation is confined inside the light cone. Also, for lower values of spin, flat-space limits are given.     

High-order FDTD methods for transverse electromagnetic systems in dispersive inhomogeneous media

This Letter introduces a novel finite-difference time-domain (FDTD) formulation for solving transverse electromagnetic systems in dispersive media. Based on the auxiliary differential equation approach, the Debye dispersion model is coupled with Maxwell's equations to derive a supplementary ordinary differential equation for describing the regularity changes in electromagnetic fields at the dispersive interface. The resulting time-dependent jump conditions are rigorously enforced in the FDTD discretization by means of the matched interface and boundary scheme. High-order convergences are numerically achieved for the first time in the literature in the FDTD simulations of dispersive inhomogeneous media.     

Simpler methods do it better: Success of Recurrence Quantification Analysis as a general purpose data analysis tool

Over the last decade, Recurrence Quantification Analysis (RQA) has become a new standard tool in the toolbox of nonlinear methodologies. In this Letter we trace the history and utility of this powerful tool and cite some common applications. RQA continues to wend its way into numerous and diverse fields of study.     

Axion-like particles,cosmic magnetic fields and gamma-ray astrophysics

Axion-like particles (ALPs) are predicted by many extensions of the Standard Model and give rise to characteristic dimming and polarization effects in a light beam travelling in a magnetic field. In this Letter, we demonstrate that photon-ALP mixing in cosmic magnetic fields produces an observable distortion in the energy spectra of distant gamma-ray sources (like AGN) for ranges of the ALP parameters allowed by all available constraints. The resulting effect is expected to show up in the energy band 100 MeV–100 GeV, and so it can be searched with the upcoming GLAST mission.     

Particle-transport analysis in reversed field pinch helical states

This Letter reports the result of a numerical study of particle transport in self-organized single helicity (SH) and quasi-SH reversed field pinch plasmas. Our code, benchmarked against experimental data, predicts a large improvement in particle transport for SH compared to the standard multiple helicity states. The contribution of neoclassical effects is noted. An estimate of the ambipolar electric field in helical states and in fully stochastic magnetic fields is given.     

Observation of second-order hyper-Raman generation in LiNbO3 whispering-gallery mode disk resonators

In this Letter we report experimental demonstration of nonlinear frequency conversion at several optical frequencies in a whispering-gallery mode resonator (WGMR). Because of the enhancement of nonlinear interactions inside a WGMR, interaction of a 1064 nm pump field with a LiNbO(3) disk produced a weak but measurable non-phase-matched 532 nm second-harmonic field at room temperature (>100 °C below the phase-matching temperature) for pump powers of a few tens of milliwatts. For higher pump powers, we observed the generation of four additional fields at 545, 559, 573, and 587 nm. The relative spectral shift between two consecutive fields corresponds to a 455 cm(-1) vibrational mode in LiNbO(3) crystal. Our preliminary analysis indicates that these fields are the result of a multiphonon hyper-Raman scattering in which two photons of the pump field are converted into one photon of a higher-frequency field and one or several optical phonons.     

Can an electric field induce an antiferroelectric phase out of a ferroelectric phase?

It has been widely accepted that electric fields favor the ferroelectric phase with parallel electric dipoles over the antiferroelectric phase. With detailed measurements in polycrystalline ceramics of Pb(0.99)Nb(0.02[(Zr(0.57)Sn(0.43)(1-y)Ti(y)](0.98)O(3), we demonstrate in this Letter that electric fields can induce an antiferroelectric phase out of a ferroelectric phase, i.e., trigger an apparently unlikely ferroelectric-to-antiferroelectric phase transition. We suggest that it is caused by the volume contraction from the converse piezoelectric effect at the coercive field with a reversed polarity.     

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.     

Expectations of Fermionic Fields with N Components

In this Letter, we show with a concrete example that the behaviour in N independent components (flavours) of the expectation of fermionic fields can be different from that suggested by its expansion in terms of Feynman graphs. To prove this result, we study the asymptotic behaviour of a nonautonomous discrete time map.     

Comment on "Resolving the wave vector and the refractive index from the coefficient of reflectance"

In a recent Letter, the reflectance coefficient was used to resolve the sign choice of the wave vector and refractive index in active media. We argue that such a coefficient loses its physical meaning for active media (at real frequencies) when the field amplification is limited only by gain saturation. In this case, the amplitude reflectance coefficient leads to fictitious noncausal reflected fields when the backward Fourier transform is used.     

Permutability property for self-dual Yang-Mills fields

A permutability property for Bäcklund transformations of the self-dual SU(2) Yang-Mills fields is shown to exist. We give a superposition-type formula, whose iteration permits the simple algebraic construction of solutions of the self-dual Yang-Mills equations.This Letter has been authored under contract DE-AC02-76H00016 with the U.S. Department of Energy.     

Bose fluids above T(c): incompressible vortex fluids and "supersolidity"

This Letter emphasizes that nonlinear rotational or diamagnetic susceptibility is characteristic of Bose fluids above their superfluid T(C)'s. For sufficiently slow rotation or, for superconductors, weak B fields, this amounts to an incompressible response to vorticity. The cause is that there are terms missing in the conventionally accepted model Hamiltonian for quantized vortices in the Bose fluid. The resulting susceptibility can account for recent observations of Chan et al. [Nature (London) 427, 225 (2004); Science 305, 1941 (2004)] on solid He and Ong et al. [Europhys. Lett. 72, 451 (2005) on cuprate superconductors.     

Probing decoherence with electromagnetically induced transparency in superconductive quantum circuits

Superconductive quantum circuits comprise quantized energy levels that may be coupled via microwave electromagnetic fields. Described in this way, one may draw a close analogy to atoms with internal (electronic) levels coupled by laser light fields. In this Letter, we present a superconductive analog to electromagnetically induced transparency that utilizes superconductive quantum circuit designs of present day experimental consideration. We discuss how a superconductive analog to electromagnetically induced transparency can be used to establish macroscopic coherence in such systems and, thereby, be utilized as a sensitive probe of decoherence.     

Piezoresponse force microscopy studies of switching behavior of ferroelectric capacitors on a 100-ns time scale

Piezoresponse force microscopy is a powerful technique for nm-scale studies but is usually limited by response time. In this Letter, we report the first direct studies of ferroelectric capacitor switching on a submicrosecond time scale. Simultaneous domain imaging and sub-mus transient current measurements establish a direct relationship between polarization P(t) and domain kinetics. Switching times scale with capacitor size over an order of magnitude. Small capacitors, where polarization reversal is dominated by domain wall motion, switch faster at high fields but more slowly at low fields while larger capacitors do the reverse.     

Amplification without population inversion in a three-level Λ-type system with an external coherent magnetic field

In this Letter, we investigate the amplification without inversion (AWI) in a new scheme, a three-level Λ-type system which the two lower states are coupled by an external magnetic field. We find that, owing to the presence of the external magnetic field, the absorption of the probing field is very sensitive to the relative phase of the probing and the pumping fields. By appropriately choosing the Rabi frequency of the pumping field, the Lamor frequency of the external magnetic field and the relative phase, AWI can be realized.