Showing papers on "Bessel beam published in 2002"
TL;DR: Bessel beams do not diverge and, furthermore, if part of the beam is obstructed or distorted the beam reconstructs itself after a characteristic propagation distance, which may be utilized within optical tweezers to trap particles in multiple, spatially separated sample cells with a single beam.
Abstract: Optical tweezers1 are commonly used for manipulating microscopic particles, with applications in cell manipulation2, colloid research3,4,5, manipulation of micromachines6 and studies of the properties of light beams7. Such tweezers work by the transfer of momentum from a tightly focused laser to the particle, which refracts and scatters the light and distorts the profile of the beam. The forces produced by this process cause the particle to be trapped near the beam focus. Conventional tweezers use gaussian light beams, which cannot trap particles in multiple locations more than a few micrometres apart in the axial direction, because of beam distortion by the particle and subsequent strong divergence from the focal plane. Bessel beams8,9, however, do not diverge and, furthermore, if part of the beam is obstructed or distorted the beam reconstructs itself after a characteristic propagation distance10. Here we show how this reconstructive property may be utilized within optical tweezers to trap particles in multiple, spatially separated sample cells with a single beam. Owing to the diffractionless nature of the Bessel beam, secondary trapped particles can reside in a second sample cell far removed (∼3 mm) from the first cell. Such tweezers could be used for the simultaneous study of identically prepared ensembles of colloids and biological matter, and potentially offer enhanced control of ‘lab-on-a-chip’ and optically driven microstructures.
914 citations
TL;DR: In this paper, the orbital angular momentum density of Bessel beams is calculated explicitly within a rigorous vectorial treatment, which allows us to investigate some aspects that have not been analysed previously, such as the angular momentum content of azimuthally and radially polarized beams.
Abstract: The orbital angular momentum density of Bessel beams is calculated explicitly within a rigorous vectorial treatment. This allows us to investigate some aspects that have not been analysed previously, such as the angular momentum content of azimuthally and radially polarized beams. Furthermore, we demonstrate experimentally the mechanical transfer of orbital angular momentum to trapped particles in optical tweezers using a high-order Bessel beam. We set transparent particles of known dimensions into rotation, where the sense of rotation can be reversed by changing the sign of the singularity. Quantitative results are obtained for rotation rates. This paper's animations are available from the Multimedia Enhancements page.
364 citations
TL;DR: In this paper, the superluminal group velocity of an ultrashort optical Bessel beam pulse is measured over its entire depth of field, corresponding to the cost of computing the traveling ionization front induced by the pulse.
Abstract: The superluminal group velocity of an ultrashort optical Bessel beam pulse is measured over its entire depth of field, corresponding to $\ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}{10}^{4}$ optical wavelengths. The method used is to measure the traveling ionization front induced by the pulse.
103 citations
24 May 2002
TL;DR: In this paper, the authors demonstrate transfer of orbital angular momentum from a high order Bessel beam to trapped transparent particles in optical tweezers by using a transfer mechanism due to scattering.
Abstract: Summary form only given. We demonstrate experimentally for the first time, that a high order Bessel beam possesses orbital angular momentum (OAM). We demonstrate transfer of OAM from such a beam to trapped transparent particles in optical tweezers. Additionally, we examine theoretically, within a rigorous vectorial treatment, the local angular momentum density for a high order Bessel beam (HOBB) and find local variations in this density when compared to Laguerre-Gaussian beams. For transparent particles the orbital angular momentum is transferred by scattering/reflection of the incident light beam as in the case of metallic particles. Importantly we obtained quantitative results for the rotation rate which has a linear dependence on the orbital angular momentum content of the light beam. The measured rotation rates correspond to a transfer of about 1% of the Bessel beam's orbital angular momentum which is consistent with calculations based on a transfer mechanism due to scattering.
71 citations
TL;DR: In this paper, a generalization of type 3 ultrashort pulses (also known as pulse beams or isodiffracting pulses) is introduced, and a model spectral distribution that is zero outside a finite range is investigated.
Abstract: A generalization of type 3 ultrashort pulses (also known as pulse beams or isodiffracting pulses) is introduced. The Bessel beam form of this generalized beam consists of pulses that propagate in free space, without spreading, with a velocity that can be less than that of light. A model spectral distribution that is zero outside a finite range is investigated.
38 citations
TL;DR: In this paper, the authors present an overview of the methods applied and results obtained with quasi-optical hologram techniques using both amplitude and phase holograms, as well as several beam shapes: plane waves, radio wave vortices and Bessel beams.
Abstract: Holograms—diffractive elements—are designed and fabricated for shaping millimetre-wave radio fields. Methods for the synthesis of hologram elements are discussed and several beam shapes are tested: plane waves, radio-wave vortices and Bessel beams. Here we present an overview of the methods applied and results obtained with quasi-optical hologram techniques using both amplitude and phase holograms.
34 citations
TL;DR: Two implementations are identified to create a Bessel beam directly, i.e. without the spatial filtering of an initially Gaussian beam, and numerical simulation to corroborate the geometrical optical arguments leads to the conclusion that anti-Stokes radiation generated in a nonlinear material will leave the substrate under the form of a B vessel.
Abstract: Two implementations are identified to create a Bessel beam directly, i.e. without the spatial filtering of an initially Gaussian beam. The first implementation is based on a resonator configuration whose lowest-loss transverse mode is a Bessel beam. Numerical simulation to corroborate the geometrical optical arguments is presented. The second implementation is based on the theorem that the angular-plane wave spectrum of a Bessel beam is composed of a cone of wave vectors. This cone is also generated through a phase-matching condition in a four-wave mixing process. This leads to the conclusion that anti-Stokes radiation generated in a nonlinear material will leave the substrate under the form of a Bessel beam.
27 citations
19 May 2002
TL;DR: The superluminal group velocity of an ultrashort optical Bessel beam pulse is measured over its entire depth of field, corresponding to approximately 2x10(4) optical wavelengths.
Abstract: Summary form only given We measured the group velocity of an ultrashort optical Bessel beam pulse over its entire depth of field using two diagnostics that are sensitive to the extremely rapid generation of plasma through field ionization of argon The almost stationary plasma that remains after field ionization ensures saturation
25 citations
TL;DR: In this article, it was shown that the velocity of fringes on the axis of propagation is superluminal and this velocity is directly measured with a slightly modified Young set-up.
22 citations
TL;DR: In this paper, the internal conical refraction of a Bessel beam of arbitrary order in biaxial and non-gyrotropic crystal plates was studied theoretically and conditions for complete conversion of the m th order beam to the beam of order m −1 or m + 1 were determined.
20 citations
TL;DR: A method for characterizing the linear field of any flat, continuous-wave annular array in terms of a set of known limited-diffraction Bessel beams using Fourier-Bessel series to model the surface pressure of the transducer surface.
Abstract: Presents a method for characterizing the linear field of any flat, continuous-wave annular array in terms of a set of known limited-diffraction Bessel beams. The technique uses Fourier-Bessel series to model the surface pressure of the transducer surface, with each term in the series giving rise to a Bessel beam with known propagation parameters. The analysis is applied numerically to two different transducers discussed previously in the literature. In both cases, a deeper understanding of the field emitted than was previously available is gained. Brief outlines for extending the technique to pulsed wave and non-annular arrays are also given.
TL;DR: In this paper, it is demonstrated that by blocking of the part of Bessel light beam azimuthal aperture, a far field ring is completely reconstructed in Azimuth and partially in intensity after the beam passes through a benzene cell.
TL;DR: This work has shown that if the light in the tweezers is a 'Bessel beam', this problem can be overcome, creating some interesting experimental possibilities.
Abstract: Optical tweezers use light to manipulate tiny particles — but only one at a time. If the light in the tweezers is a 'Bessel beam', this problem can be overcome, creating some interesting experimental possibilities.
TL;DR: In this paper, a Bessel beam that impinges at oblique incidence onto a layer in such a way that each plane-wave component impinges with an angle larger than the critical angle was examined.
TL;DR: In this paper, a modal theory of propagation-invariant optical fields was proposed, and the existence of light string and light capillary beams was predicted within the framework of this theory.
TL;DR: In this paper, theoretical studies and computer simulations of the resonant excitation of Langmuir waves during the ionization of a homogeneous gas by high-intensity laser radiation are presented.
Abstract: Results are presented from theoretical studies and computer simulations of the resonant excitation of Langmuir waves during the ionization of a homogeneous gas by high-intensity laser radiation. Two mechanisms for the formation of nonuniform resonant structures in the discharge are examined: plasma-resonance ionization instability, resulting in the density modulation along the electric field vector, and gas breakdown in the field of a transversely inhomogeneous laser beam (a Bessel beam produced by an axicon lens). In both cases, the transition of the plasma density through the critical value is accompanied by the generation of intense Langmuir waves, the formation of fast ionization fronts, and the appearance of long-lived quasi-turbulent states.
TL;DR: In this paper, the authors proved that the axis of the non-diffracting beam produced by an axicon is very stable and can be adopted as the datum line to measure the spatial straightness error in continuous working distance, which may be short, medium or long.
Abstract: Because of the large beam diameter and special characteristics of the non-diffracting beam produced by an axicon, the non-diffracting beam can tolerate the eccentricity of the incident laser beam's axis to the axicon. The non-diffracting beam obtains the additional tolerance property to the incident light beam's deflection when adopting a kind of incident divergent sphere Gauss wave, and this is proved in this paper through theoretical analysis and practical tests. The obtained conclusion is that the axis of the non-diffracting beam produced by an axicon is very stable and can be adopted as the datum line to measure the spatial straightness error in continuous working distance, which may be short, medium or long.
TL;DR: In this paper, the cooperative effects on optical forces in a system of N two level atoms confined to a volume of dimension less than λ3, where λ is radiation wavelength and driven by a coherent radiation field with a spatial profile like Laguerre-Gaussian or ideal Bessel beam were investigated.
Abstract: We investigate the cooperative effects on optical forces in a system of N two level atoms confined to a volume of dimension less than λ3, where λ is radiation wavelength and driven by a coherent radiation field with a spatial profile like Laguerre–Gaussian or ideal Bessel beam. We show a dramatic enhancement on optical forces as well as on the angular momentum imparted to the atom by a factor of N2.
TL;DR: Propagation-invariant electromagnetic beams, propagating along the optical axis of a uniaxially anisotropic crystal, are investigated in this paper, where an analytical expression of the Poynting vector reveals an azimuthal transverse energy flow that becomes pure longitudinal if the complex amplitudes of the ordinary and extraordinary fields are either in phase or in phase opposition.
Abstract: Propagation-invariant electromagnetic beams, propagating along the optical axis of a uniaxially anisotropic crystal, are investigated. The beams are a superposition of propagation-invariant ordinary and extraordinary fields, with different polarizations states and Bessel profiles. The analytical expression of the Poynting vector reveals an azimuthal transverse energy flow that becomes pure longitudinal, if the complex amplitudes of the ordinary and extraordinary fields are either in phase or in phase opposition.
TL;DR: In this paper, a new concept and a method are presented to obtain a laser beam output with high luminance and quality, instead of using the conventional concept of obtaining a single transverse mode through compressing the oscillating mode volume using a small aperture diaphragm, the large multimode volume and the high output power are obtained by studying the physical mechanism of the expansion and coupling between a Bessel beam and a Gaussian beam.
Abstract: A new concept and the method are presented to obtain a laser beam output with high luminance and quality. Instead of using the conventional concept of “obtaining a single transverse mode through compressing the oscillating mode volume using a small aperture diaphragm”, the large multimode volume and the high output power are obtained by studying the physical mechanism of the expansion and coupling between a Bessel beam and a Gaussian beam. A high quality light beam (close to the diffraction limit) with high luminance and large intensity difference between the center and the edge is achieved simultaneously.
TL;DR: In this paper, the internal conical refraction of a Bessel beam of arbitrary order was studied theoretically and conditions for complete conversion of a beam of the order m to Bessel beams of order m−1 or m+1 with orthogonal circular polarizations were determined.
Abstract: The internal conical refraction of a Bessel beam of arbitrary order is studied theoretically. It is shown that a beam of the order m of arbitrary polarization in the general case is partially converted to Bessel beams of the order m ± 1 with orthogonal circular polarizations. Conditions for complete conversion of a beam of the order m to a Bessel beam of the order m−1 or m+1 are determined.
01 Jan 2002
01 Oct 2002
TL;DR: Propagation-invariant fields of the third kind are defined on the base of a modal theory proposed recently by authors as mentioned in this paper, and the physical nature of these fields is discussed and their examples are illustrated by numerical simulation.
Abstract: Propagation-invariant fields of the third kind are defined on the base of a modal theory proposed recently by authors. The physical nature of these fields is discussed and their examples are illustrated by numerical simulation.
01 Jan 2002
TL;DR: In this article, a finite element simulator for ultrasonic fields using the numerical programming library Diffpack is presented. But the main content of this paper is on the linear model, but also include some recent developments on propagation in nonlinear medium.
Abstract: This article reports some preliminary results in the development of a finite element simulator for ultrasonic fields using the numerical programming library Diffpack. In our present work, we are combining the study of linearly–based limited diffraction beams (Bessel beams and X–Waves) with the development of a finite element package for analysis of linear and nonlinear media in order to compare how such waves behave in the two cases. The medium may be either homogeneous or inhomogeneous. The main content of this paper is on the linear model, but we also include some recent developments on propagation in nonlinear medium.
30 Aug 2002
TL;DR: In this paper, a computer generated hologram (CGH) was used to generate a Bessel beam from a Gaussian laser beam and the axial intensity was measured for the beam propagation distances.
Abstract: Bessel beams are a special class of diffraction-free solutions of the wave equation which are of practical interest, for example, in precision alignment, laser machining and laser surgery. Therefore efficient methods for the transformation of a Gaussian laser beam into a Bessel beam are needed. We design and fabricate computer generated holograms(CGH) to generate this Bessel beam. Designed CGH is recorded onto the photopolymer which is used as a volume hologram material making CGHOE(computer generated holographic optical element). The principle of the CGH and the propagation characteristics of the Bessel beam are explained. The binary mask designed for generating Bessel beam is copied on photopolymer by the contact copy method. The axial intensity is measured for the beam propagation distances. The propagation property and the intensity profile of the Bessel beam are analyzed.
08 Oct 2002
TL;DR: In this article, a procedure for decomposing the linear field of flat pulsed wave annular arrays into an equivalent set of known limited diffraction Bessel beams is presented, enabling good insight into the propagation of annular fields to be obtained.
Abstract: A procedure is provided for decomposing the linear field of flat pulsed wave annular arrays into an equivalent set of known limited diffraction Bessel beams. Each Bessel beam propagates with known characteristics, enabling good insight into the propagation of annular fields to be obtained. Numerical examples are given in the context of a 10-ring annular array operating at a central frequency of 2.5 MHz in water.
22 Jul 2002
TL;DR: In this article, the experimental results of an investigation of the self-action of Bessel beam propagating in benzene are presented, and the typical modifications of the far-field intensity distribution of the beam caused by its self action are revealed.
Abstract: The experimental results of an investigation of the self- action of Bessel beam propagating in the benzene are presented. The typical modifications of the far-field intensity distribution of Bessel beam caused by its self- action are revealed. A good agreement with computer simulation results is obtained.
10 Nov 2002
TL;DR: In this paper, the authors describe the apparent superluminal behavior of the interference pattern in front of an axicon lens using terahertz spectroscopy, and they report direct observations of superlumininal phase and group velocities, both of which are only weak functions of frequency.
Abstract: Summary form only given. We describe the apparent superluminal behavior of the interference pattern in front of an axicon lens using terahertz spectroscopy. The ability to coherently detect the electric field permits a more complete characterization of this Bessel beam than has been previously reported. We report direct observations of superluminal phase and group velocities, both of which are only weak functions of frequency. As a result, it is possible to discount pulse reshaping effects in the consideration of experiments of this type. We also expect that the extended Rayleigh range of these Bessel beams should be useful for enhanced depth-of-field terahertz imaging.
30 Apr 2002
TL;DR: In this article, a pseudo-nondiffracting Bessel light beam with phase singularities of different topological charge has been developed and proved experimentally, and the possibility of realization of arithmetic operations using this principle is proved.
Abstract: New methods for production of pseudo-nondiffracting Bessel light beams with phase singularities of different topological charge have been developed and proved experimentally. It is found out that nonlinear-optical processes of frequency doubling and sum-frequency generation allow to control formation and annihilation of dislocations. The possibility of realization of arithmetic operations using this principle is proved. When Gaussian beam interferes with M-order Bessel beam having M-order dislocation, the dislocation disintegrates on M parallel quasi-nondiffracting beams packed compactly. Rotating of optical beams aggregate on required angle takes place when phase difference between interfering fields is modulated. New principle of optical inter-connections is proposed on this base.