Generation Of Bessel Beams Research Articles

Efficient generation of an arbitrary nondiffracting Bessel beam employing its phase modulation

We report a highly efficient method for generation of any high-order nondiffracting Bessel beam employing a phase hologram whose transmittance coincides with the phase modulation of such a beam. It is remarkable that the Bessel beam generated by this hologram, at the plane of this device, has peak amplitude higher than the amplitude of the beam employed to illuminate it.

Discrete diffraction and shape-invariant beams in optical waveguide arrays

General properties of linear propagation of discretized light in homogeneous and curved waveguide arrays are comprehensively investigated and compared to those of paraxial diffraction in continuous media. In particular, general laws describing beam spreading, beam decay, and discrete far-field patterns in homogeneous arrays are derived using the method of moments and the steepest-descent method. In curved arrays, the method of moments is extended to describe evolution of global beam parameters. A family of beams which propagate in curved arrays maintaining their functional shape---referred to as discrete Bessel beams---is also introduced. Propagation of discrete Bessel beams in waveguide arrays is simply described by the evolution of a complex-$q$ parameter similar to the complex-$q$ parameter used for Gaussian beams in continuous lensguide media. A few applications of the $q$ parameter formalism are discussed, including beam collimation and polygonal optical Bloch oscillations.

Generation of Bessel beams using a terahertz quantum cascade laser

We report the generation of Bessel beams using polytetrafluoroethene conical lenses and a quantum cascade laser emitting at 2.8 THz. The formation of a central beam spot that retains its size over distances exceeding the characteristic Rayleigh range is demonstrated, and the power transport properties of these beams are compared with those obtained using parabolic reflectors. These lenses could provide an attractive alternative to parabolic reflectors for terahertz imaging applications where a large depth of focus and/or efficient and controllable coupling of radiation onto a small target are desirable.

Realization of an evanescent Bessel beam via surface plasmon interference excited by a radially polarized beam

We report the experimental confirmation of the evanescent Bessel beam generation via surface plamson resonance excitation with a radially polarized beam. The interference of surface plasmon waves excited by a radially polarized beam creates an evanescent Bessel beam with enhanced localized field and spot size beyond the diffraction limit. The excitation of the surface plasmon is confirmed by the observation of a narrow dark ring at the back focal plane. Two-dimensional intensity distributions at different distances from the sample surface are mapped by a collection-mode near-field scanning optical microscope to verify the nondiffracting and decaying natures of the evanescent Bessel beam.

Generation and amplification of pulsed Bessel beams by seeding an optical parametric amplifier

By using two very different seed pulses we demonstrate that the spatiotemporal gain properties of a chi(2) optical parametric amplifier can be exploited as an efficient conical reshaping mechanism leading to the generation and amplification of a pulsed Bessel beam.

Generation of multiple Bessel beams for a biophotonics workstation

We present a simple method using an axicon and spatial light modulator to create multiple parallel Bessel beams and precisely control their individual positions in three dimensions. This technique is tested as an alternative to classical holographic beam shaping commonly used now in optical tweezers. Various applications of precise control of multiple Bessel beams are demonstrated within a single microscope giving rise to new methods for three-dimensional positional control of trapped particles or active sorting of micro-objects as well as "focus-free" photoporation of living cells. Overall this concept is termed a 'biophotonics workstation' where users may readily trap, sort and porate material using Bessel light modes in a microscope.

Intensity transformation of vector Bessel beams using a multilayer system

We theoretically investigate the generation of vector Bessel beams of the order m using a phase shifted superposition of TE and TM electromagnetic Bessel beams. Such Bessel beams are characterized by the intensity profile described by the superposition of squared Bessel functions of the orders (m-1) and (m+1). We derive the conditions for creating the special distributions of the intensity, which are determined by only one Bessel function, Jm-12 or Jm+12. We offer the approach of intensity transformation based on the Bessel beam transmission through a multilayer system. Finally, we reveal the perfect intensity transformation transferring the whole energy from Jm-12- to Jm+12-profile of intensity distribution.

Generation of Second-Harmonic Bessel Beams by Transverse Phase-Matching in Annular Periodically Poled Structures

We demonstrate experimentally the generation of second-harmonic conical waves via parametric frequency doubling in a two-dimensional annular periodically poled nonlinear photonic structure fabricated in a stoichiometric lithium tantalate crystal. We apply the concept of nonlinear Bragg diffraction for explaining this effect, and show theoretically that in low-symmetry crystals this process results in generated second-harmonic waves being a superposition of the Bessel beams.

Tunable generation of Bessel beams with a fluidic axicon

This paper describes a tunable fluidic conical lens, or axicon, for the generation and dynamic reconfiguration of Bessel beams. When illuminated with a Gaussian laser beam, our fluidic axicon generates a diverging beam with an annular cross section. By varying the refractive index of the solution that fills our device, we can vary easily the spatial properties of the resulting Bessel beam.

Generation of Bessel Beams at mm- and Sub mm-wavelengths by Binary Optical Elements

In this paper, binary optical elements (BOE’s) are designed for generating Bessel beams at mm- and sub mm- wavelengths. The design tool is to combine a genetic algorithm (GA) for global optimization with a two-dimension finite-difference time-domain (2-D FDTD) method for rigorous electromagnetic computation. The design process for converting a normally incident Gaussian beam into a Bessel beam is described in detail. Numerical results demonstrate that the designed BOE’s can not only successfully produce arbitrary order Bessel beams, but also have higher diffraction efficiencies when compared with amplitude holograms.

Solid immersion axicon: maximizing nondiffracting or Bessel beam resolution

A new type of optical configuration--a solid immersion axicon (SIAX)--is proposed. Similar to a solid immersion lens for Gaussian beams, a SIAX increases the diffraction-limited resolution for propagating Bessel beams by a factor of the refractive index of the media. For incident radial polarization, the scheme generates the smallest focal spot available for nondiffracting beams. The configuration can be implemented with either refractive or diffractive axicons. The scheme may find use in microscopy, imaging, lithography and data storage, and other applications requiring nondiffracting beam characteristic features such as very large focal depth.

Generation of Bessel beams by parametric frequency doubling in annular nonlinear periodic structures

We analyze the second-harmonic generation in two-dimensional photonic structures with radially periodic domains created by poling of a nonlinear quadratic crystal. We demonstrate that the parametric conversion of the Gaussian fundamental beam propagating along the axis of the annular structure leads to the axial emission of the second-harmonic field in the form of the radially polarized first-order Bessel beam.

Negative propagation of vector Bessel beams

Energy characteristics of the superposition of TE- and TM-polarized electromagnetic Bessel beams are studied. For some phase differences between TE and TM waves the components of the Poynting vector vary in sign. We call this situation "negative propagation," because locally the beam may behave like a wave propagating in the direction opposite to the conventional one. We predict the following phenomena, which should confirm negative beam propagation: reflection of the beam from a circular aperture and unusual movement of microparticles in the beam.

Generation of achromatic Bessel beams using a compensated spatial light modulator

We report the creation of white-light, achromatic Bessel beams using a spatial light modulator and a prism to compensate for the dispersion. Unlike the Bessel beam created by a refractive axicon, this achromatic beam has a radial wavevector and hence an intensity cross-section which is independent of wavelength. The technique also lends itself to the generation of higher order Bessel beams with an on-axis optical vortex and associated orbital angular momentum.

Evanescent Bessel beam generation via surface plasmon resonance excitation by a radially polarized beam

A simple setup for generating evanescent Bessel beams is proposed. When a radially polarized beam is strongly focused onto a dielectric-metal interface, the entire beam is p-polarized with respect to the dielectric-metal interface, enabling excitation of surface plasmons from all directions. The angular selectivity of surface plasmon excitation mimics the function of an axicon, leading to an evanescent nondiffracting Bessel beam. The created evanescent Bessel beam may be used as a virtual probe for near-field optical imaging and sensing applications.

Wavelength dependent propagation and reconstruction of white light Bessel beams

Bessel beams are propagation invariant light fields. It has very recently been shown that they may be created with temporally incoherent (white) light. Such fields may have applications in low coherence interferometric imaging for biomedicine and optical micromanipulation. White light Bessel beams may be deemed at first glance to generate a white focal line of light at the beam centre due to the absence of chromatic aberration. We investigate the spectral characteristics of the reformation or self-healing of this light field in the presence of a circular obstruction and reveal that the spectral characteristics of the beam generation and reformation results in a dispersive focal line at the beam centre which is 'white' only over a certain region.

Generation of an elliptic Bessel beam

In an elliptic coordinate system the solution for a diffraction-free beam is given by a Mathieu beam, which is mathematically complicated and therefore takes considerable computational time and a large memory space. A technique is reported for the generation of elliptic hollow beams, which are actually scaled versions of higher-order Bessel beams. The analysis is based on the fact that stretching coordinates in the space domain results in a contraction of the coordinates in the frequency domain, along with a change in the overall amplitude of the spectrum. The beam, produced holographically, is structurally stable and retains its shape up to approximately 1 m.

Demonstration experiments on nondiffracting beams generated by thermal light

Nondiffracting (Bessel) beams are normally generated using fully coherent light (a laser). Yet their distinctive properties (nondiffraction and self-reconstruction) can be obtained using a common halogen lamp as the primary source. Other experiments, for example, the creation of periodic intensity modulations along the optical axis, require a source with a much narrower spectrum. We present demonstrations that show that thermal light is useful for explaining several properties of a Bessel-beam generator and may help students to understand some issues of modern coherence theory.

Fabrication of efficient microaxicon by direct electron-beam lithography for long nondiffracting distance of Bessel beams for optical manipulation

We demonstrate a fabrication technique in the realization of microaxicon by single-step processing via electron-beam lithography. Microaxicon is used for the generation of propagation-invariant Bessel beams which find tremendous applications in optical trapping. The proposed technique is a simple, reliable, and reproducible method for the production of high-quality Bessel beams with long propagation-invariant distances, in our configuration, in excess of 20cm. Such Bessel beams with long nondiffracting distances are essential for optical tweezers systems in many cases.

Generating Bessel beams by use of localized modes

We propose a novel method for generating both propagating and evanescent Bessel beams. To generate propagating Bessel beams we propose using a pair of distributed Bragg reflectors (DBRs) with a resonant point source on one side of the system. Those modes that couple with the localized modes supported by the DBR system will be selectively transmitted. This is used to produce a single narrow band of transmission in kappa space that, combined with the circular symmetry of the system, yields a propagating Bessel beam. We present numerical simulations showing that a propagating Bessel beam with central spot size of approximately 0.5lambda0 can be maintained for a distance in excess of 3000lambda0. To generate evanescent Bessel beams we propose using transmission of a resonant point source through a thin film. A transmission resonance is produced as a result of the multiple scattering occurring between the interfaces. This narrow resonance combined with the circular symmetry of the system corresponds to an evanescent Bessel beam. Because propagating modes are also transmitted, although the evanescent transmission resonance is many orders of magnitude greater than the transmission for the propagating modes, within a certain distance the propagating modes swamp the exponentially decaying evanescent ones. Thus there is only a certain regime in which evanescent Bessel beams dominate. However, within this regime the central spot size of the beam can be made significantly smaller than the wavelength of light used. Thus evanescent Bessel beams may have technical application, in high-density recording for example. We present numerical simulations showing that with a simple glass thin film an evanescent Bessel beam with central spot size of approximately 0.34lambda0 can be maintained for a distance of 0.14lambda0. By choice of different material parameters, the central spot size can be made smaller still.