Bessel Beam Research Papers - Academia.edu (original) (raw)

Motivated by the recent discovery of electron vortex beams carrying orbital angular momentum (AM), we construct exact Bessel-beam solutions of the Dirac equation. They describe relativistic and nonparaxial corrections to the scalar... more

Motivated by the recent discovery of electron vortex beams carrying orbital angular momentum (AM), we construct exact Bessel-beam solutions of the Dirac equation. They describe relativistic and nonparaxial corrections to the scalar electron beams. We describe the spin and orbital AM of the electron with Berry-phase corrections and predict the intrinsic spin-orbit coupling in free space. This can be observed as a spin-dependent probability distribution of the focused electron vortex beams. Moreover, the magnetic moment is calculated, which shows different g factors for spin and orbital AM and also contains the Berry-phase correction.

In this work a dielectric planar lens is proposed to generate a Bessel beam. The lens works at Ka-band and produces a non-diffraction range within the Fresnel region of the antenna. The methodology to design the aperture antenna at... more

In this work a dielectric planar lens is proposed to generate a Bessel beam. The lens works at Ka-band and produces a non-diffraction range within the Fresnel region of the antenna. The methodology to design the aperture antenna at millimetre or microwave frequencies is presented. It is applied to a dielectric planar lens made up of cells that shapes the radiated near-field by adjusting the unit cell response. An approach based on a second order polynomial is proposed to consider the angular dependence of the phase-shift response of the cell in the designing process. In order to implement the lens physically, two novel cells, based on rectangular and hexagonal prisms, are proposed, and their performance is compared. The cells ensure the index dielectric media variation using airgaps to control the overall density of the material. After fully characterizing the cells, a design is carried out for the two proposed type of cells. The requirement for the Bessel beam is a depth-of-field of 650 mm at 28 GHz. After evaluating the design in a full-wave simulation, both prototypes were manufactured using a 3-D printing technique. Finally, the prototypes were measured in a planar acquisition range to evaluate the performances of the Bessel beam. Both lenses show a good agreement between simulations and measurements, obtaining promising results in the Bessel beam generation by index-graded dielectric lenses at Ka-band. INDEX TERMS Dielectric lenses, Bessel beams, near-field focusing.

We focused here on the real shape of the tip of the axicon - which is not sharp but rather oblate. We simulated numerically and verified experimentally that tiny deviations of the tip shape from the ideal sharp profile induce significant... more

We focused here on the real shape of the tip of the axicon - which is not sharp but rather oblate. We simulated numerically and verified experimentally that tiny deviations of the tip shape from the ideal sharp profile induce significant oscillations of the beam intensity along its propagation. Such unwanted intensity modulation disturbs the unique properties of the quasi-Bessel beam - constant shape of the lateral intensity profile and especially slow variation of the on-axis intensity along the beam propagation. We demonstrate how the spatial filtration of the beam in the Fourier plane removes such undesired modulation and restores the properties of the quasi-Bessel beam.

—The paper presents the analysis and design of Bessel beam launchers using a finite inward cylindrical traveling wave aperture field distribution. The launcher radiates an electric field whose normal or longitudinal component takes the... more

—The paper presents the analysis and design of Bessel beam launchers using a finite inward cylindrical traveling wave aperture field distribution. The launcher radiates an electric field whose normal or longitudinal component takes the form of a zeroth-order Bessel function. The nondiffractive behavior of the structure in a well-defined area close to the radiating aperture is analyzed by decomposing the radiated field in its geometrical optics (GO) and diffractive (D) contributions. A closed-form expression is provided for the GO contribution whereas an asymp-totic approximation is provided for the diffractive part. Such theoretical analysis allows a precise definition of the nondiffrac-tive region for the generated Bessel beam. At the same time, it also highlights and predicts the oscillating behavior of the longitudinal component of the electric field along the z-axis due to the diffraction from the edges of the aperture. The proposed analysis is validated by a prototype at 30 GHz made by a radial waveguide loaded with metallic gratings and centrally fed by a coaxial probe. Measurement results for the longitudinal component of the electric field are in excellent agreement with full-wave results. In addition , the nondiffractive behavior for the radiated beam is reported over a bandwidth larger than 6.5% around 30 GHz. This behavior is peculiar of the nonresonant first kind Hankel aperture field distribution used for the generation of the Bessel beam.

An approximation to a Bessel beam produced by tightly focusing linearly polarized light is known to produce a smaller central lobe than focusing plane polarized light. This is because the plane polarized wave gives a broad central lobe... more

An approximation to a Bessel beam produced by tightly focusing linearly polarized light is known to produce a smaller central lobe than focusing plane polarized light. This is because the plane polarized wave gives a broad central lobe caused mainly by a parasitic longitudinal field component. It is known that this problem can be overcome by focusing radially polarized light. Here we demonstrate that other polarization distributions based on a linear combination of transverse electric (TE1) and transverse magnetic (TM1) fields can give a beam even narrower than for the radially polarized case. Special cases of this combination are identified, corresponding to the smallest width (TE1), and the maximum peak intensity compared with the side lobes (electric dipole polarization). Axially-symmetric forms can be generated by illumination with elliptically polarized light. A particular case is azimuthal polarization with a phase singularity, which is equivalent to TE1. For a semi-angular aperture of 60°, the TE1 case gives a central lobe width 9% narrower than for radially polarized illumination, while for plane polarized illumination it is 12% wider than the radially polarized case.

The generation of spatiotemporal optical wave packets that are impervious to both dispersion and diffraction has been a fascinating challenge. Despite intense research activity, such localized waves, referred to as light bullets, have... more

The generation of spatiotemporal optical wave packets that are impervious to both dispersion and diffraction has been a fascinating challenge. Despite intense research activity, such localized waves, referred to as light bullets, have remained elusive. In nonlinear propagation, three-dimensional light bullets tend to disintegrate as a result of inherent instabilities. Three-dimensional wave packets that propagate linearly have been reported, but

In this paper the focusing capability of a radiating aperture implementing an inward cylindrical traveling wave tangential electric field distribution directed along a fixed polarization unit vector is investigated. In particular, it is... more

In this paper the focusing capability of a radiating aperture implementing an inward cylindrical traveling wave tangential electric field distribution directed along a fixed polarization unit vector is investigated. In particular, it is shown that such an aperture distribution generates a non-diffractive Bessel beam whose transverse component (with respect to the normal of the radiating aperture) of the electric field takes the form of a zero-th order Bessel function. As a practical implementation of the theoretical analysis, a circular-polarized Bessel beam launcher, made by a radial parallel plate waveguide loaded with several slot pairs, arranged on a spiral pattern, is designed and optimized. The proposed launcher performance agrees with the theoretical model and exhibits an excellent polarization purity.

Quantitative analysis of the damping of magnet oscillations by eddy currents in aluminum foil Am. J. Phys. 80, 804 (2012) Rolling magnets down a conductive hill: Revisiting a classic demonstration of the effects of eddy currents Am. J.... more

Quantitative analysis of the damping of magnet oscillations by eddy currents in aluminum foil Am. J. Phys. 80, 804 (2012) Rolling magnets down a conductive hill: Revisiting a classic demonstration of the effects of eddy currents Am. J. Phys. 80, 800 (2012) An undergraduate measurement of radiative broadening in atomic vapor Am. J. Phys. 80, 740 (2012) Vibrational spectra of N2: An advanced undergraduate laboratory in atomic and molecular spectroscopy Am. J. Phys. 80, 664 (2012) Analysis of light scattered by a capillary to measure a liquid's index of refraction Am. J. Phys. 80, 688 (2012) Additional information on Am. J. Phys. Journal Homepage: http://ajp.aapt.org/ Journal Information: http://ajp.aapt.org/about/about_the_journal Top downloads: http://ajp.aapt.org/most_downloaded Information for Authors: We demonstrate a simple and straightforward method of producing Bessel beams using a 4-f spatial filtering system that requires no specialized optical components. The experiment employs the established technique of diffraction from a thin ring source, but the ring source is produced by the high-pass filtering of a uniformly illuminated circular aperture, yielding Bessel beams with a central spot radius of less than 35 m which persist over a distance of 160 mm. The experiment unifies diffraction theory, Fourier optics, and the properties of Bessel beams in a manner appropriate for an advanced undergraduate laboratory.

Femtosecond photoporation is an optical method for the injection of membrane impermeable substances into cells. Typically this is a low-throughput method where each cell is individually targeted. Here, we present a novel microfluidic... more

Femtosecond photoporation is an optical method for the injection of membrane impermeable substances into cells. Typically this is a low-throughput method where each cell is individually targeted. Here, we present a novel microfluidic platform with passive optical injection improving previously reported throughputs by one order of magnitude. In this new geometry, two-dimensional hydrodynamic focusing is achieved using a three-dimensional nozzle which confines mammalian cells to the central region of the microfluidic channel. A reusable quartz chip is designed so that a propagation invariant, 'non-diffracting' Bessel beam can be directed along the centre of the channel, parallel to but counter-propagating with the flow of cells in contrast to previous orthogonal geometries. This allows for higher flow speeds to be used whilst maintaining the necessary dwell time for cells in the core of the Bessel beam. Using this method, we have achieved viable injection of HL60 cells with propidium iodide with an efficiency of 20.4 ¡ 4.2% and CHO-K1 cells (31.0 ¡ 9.5%) at a rate of up to 10 cells s 21 .

In this paper, we consider the propagation of an high-order Bessel -Gaussian beam through the free space, ABCD lens optical system and lens axicon system. Based on the generalized diffraction Integrals, a general propagating formula of... more

In this paper, we consider the propagation of an high-order Bessel -Gaussian beam through the free space, ABCD lens optical system and lens axicon system. Based on the generalized diffraction Integrals, a general propagating formula of high-order Bessel beams is derived. Based on the derived formula of high-order Bessel beams passed through the ABCD optical system are numerically illustrated. From the numerical results we can get that when high-order Bessel beams propagates through a optical system, the shape of the output changes as the propagation distance increases, and the center of the output beam is effected by the parameters and can be controlled by adjusting them. This method, provides a convenient tool for the studying the propagation properties of high-order Bessel Gaussian beams.

There exist two well established methods to trap charged particles: the Penning trap and the Paul trap. The subject of this article is to present a third mechanism for trapping charged particles - trapping by beams of electromagnetic... more

There exist two well established methods to trap charged particles: the Penning trap and the Paul trap. The subject of this article is to present a third mechanism for trapping charged particles - trapping by beams of electromagnetic radiation. The essential role is played by the electric field configuration in the plane perpendicular to the beam axis (for nonrelativistic electrons, the magnetic field is less important). Particles are confined to the vicinity of the minimum-energy points. In particular, for beams of electromagnetic radiation carrying orbital angular momentum such points lie on the beam axis.

A method to obtain spiral fringes and embedded vortices is presented. Both beam Bessel obstruction and interference with a reference wave are involved. Corresponding phase reconstruction is achieved with single shot phase-shifting... more

A method to obtain spiral fringes and embedded vortices is presented. Both beam Bessel obstruction and interference with a reference wave are involved. Corresponding phase reconstruction is achieved with single shot phase-shifting interferometry.