Spatial and temporal characterization of a Bessel beam produced using a conical mirror

Kuntz, Katanya B.; Braverman, Boris; Youn, Sung Won; Lobino, Mirko; Pessina, E. M.; Lvovsky, A. I.

doi:10.1103/physreva.79.043802

Cited by 50 publications

(21 citation statements)

References 39 publications

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“…This method is realized by using a 90°apex-angle concave conical mirror along with a radially polarized incident beam of a specific field distribution. The cross section of the created field indicates that it is a Bessel field, and before this, studies [37][38][39] using a shallow concave conical mirror along with a linearly polarized incident beam have already tried to form Bessel fields [40,41], but with a much wider focal spot. Our calculation results show that, with a 90°apex-angle concave conical mirror, an axial field with a length (FWHM) of 50; 000λ and a width (FWHM) of 0.36λ can be created, and it has uniform intensity distribution along the axis and high optical efficiency.…”

Section: Methodsmentioning

confidence: 99%

Creation of a 50,000λ long needle-like field with 036λ width

2014

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It is a great challenge to create a needle-like field with properties of long beam length, narrow lateral width, uniformity, and high optical efficiency. Here we show a method that can realize these properties all at once. The key element is a 90° apex-angle concave conical mirror. By using this condenser along with a radially polarized incident beam of a specific field distribution, we numerically created a super slim, uniform, pure needle-like axially polarized field. This axially polarized field has a length of 50,000λ along the optical axis, and its lateral width still maintains a minimum 0.36λ size.

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Section: Methodsmentioning

confidence: 99%

Creation of a 50,000λ long needle-like field with 036λ width

2014

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“…The resulting phase velocity and group velocity along z are This modification of the phase and group velocities of Bessel beams has been examined in the classical, many-photon regime. Subtle changes in velocity have been previously studied using Bessel beams in the microwave (12) and optical regimes (13)(14)(15).…”

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confidence: 99%

Spatially structured photons that travel in free space slower than the speed of light

Giovannini¹,

Romero²,

Potoček³

et al. 2015

Science

157

171

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Abstract:That the speed of light in free space is constant is a cornerstone of modern physics. However, light beams have finite transverse size, which leads to a modification of their wavevectors resulting in a change to their phase and group velocities. We study the group velocity of single photons by measuring a change in their arrival time that results from changing the beam's transverse spatial structure. Using time-correlated photon pairs we show a reduction of the group velocity of photons in both a Bessel beam and photons in a focused Gaussian beam. In both cases, the delay is several micrometers over a propagation distance of the order of 1 m. Our work highlights that, even in free space, the invariance of the speed of light only applies to plane waves. Main textThe speed of light is trivially given as / , where is the speed of light in free space and is the refractive index of the medium. In free space, where = 1, the speed of light is simply . We show that the introduction of transverse structure to the light beam reduces the group velocity by an amount depending upon the aperture of the optical system. The delay corresponding to this reduction in the group velocity can be greater than the optical wavelength and consequently should not be confused with the HÀ Gouy phase shift (1, 2). To emphasize that this effect is both a linear and intrinsic property of light, we measure the delay as a function of the transverse spatial structure of single photons.The slowing down of light that we observe in free space should also not be confused with slow, or indeed fast, light associated with propagation in highly nonlinear or structured materials (3,4). Even in the absence of a medium, the modification of the speed of light has previously been known. For example, within a hollow waveguide, the wavevector along the guide is reduced below the free-space value, leading to a phase velocity greater than . Within the hollow waveguide, the product of the phase and group velocities is given as , = 2 , thereby resulting in a group velocity , along the waveguide less than (5). 2Although this relation for group and phase velocities is derived for the case of a hollow waveguide, the waveguide material properties are irrelevant. It is the transverse spatial confinement of the field that leads to a modification of the axial component of the wavevector, . In general, for light of wavelength , the magnitude of the wavevector, 0 = 2 / , and its Cartesian components { , , } are related through (5)All optical modes of finite , spatial extent require non-zero and , which implies < 0 , giving a corresponding modification of both the phase and group velocities of the light. In this sense, light beams with non-zero k x and k y are naturally dispersive, even in free space. Extending upon the case of a mode within a hollow waveguide, an example of a structured beam is a Bessel beam (Fig. 1A), which is itself the description of a mode within a circular waveguide (1, 6). In free space, Bessel beams can be created using an axicon, or its dif...

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“…The angle at the vertex of the cone is π − γ mir , where γ mir is small. It follows from geometrical optics that the transfer function of the conical mirror is given by [9,10] …”

Section: 42mentioning

confidence: 99%

Formation of Bessel light pulses by means of a conical mirror

Ushakova

Курилкина

2011

J Appl Spectrosc

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535.42The feasibility of forming diffractionless Bessel light pulses by means of a conical mirror is demonstrated. The dependence of the spatial-temporal and energy characteristics of these pulses on the mirror parameters is examined.Introduction. Monochromatic Bessel light beams (BLB) [1] are currently in widespread use for controlling micro-and nanoparticles [2], precision materials processing [3], and probing of biological objects and the atmosphere [4]. This is because of their unique properties: they are diffractionless, i.e., the divergence of their central maximum is substantially smaller than for traditional beams within a certain region of space, and their transverse intensity profile can be recovered after encountering obstacles. At the same time, there have been few studies of pulsed Bessel light fields made up of a superposition of BLB whose frequencies lie within a certain interval. These fields can combine the advantages of monochromatic BLB and ultrashort pulses with a high local luminous energy, so they offer some promise for use in ranging systems, for controlling electrical discharges [5], and for forming cluster plasmas [6].Monochromatic BLB are most often produced by methods based on annular diaphragms and lenses [7], as well as on axicons [8]. When these methods are used to create ultrashort Bessel light pulses (BLP), distortions of the pulse envelope owing to dispersion can have a significant effect. In this paper we argue the possibility of obtaining BLP by means of a conical mirror. The advantage of mirrors is the absence of dispersion. Special attention is devoted to the question of how the mirror parameters affect the spatial and temporal characteristics of the resulting light field.Formation of a Bessel Light Pulse by Means of a Conical Mirror. Consider a conical mirror (Fig. 1) consisting of a surface of conical shape with a reflectivity close to 100%. The angle at the vertex of the cone is π − γ mir , where γ mir is small. It follows from geometrical optics that the transfer function of the conical mirror is given by [9,10]

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Spatial and temporal characterization of a Bessel beam produced using a conical mirror

Cited by 50 publications

References 39 publications

Creation of a 50,000λ long needle-like field with 036λ width

Creation of a 50,000λ long needle-like field with 036λ width

Spatially structured photons that travel in free space slower than the speed of light

Formation of Bessel light pulses by means of a conical mirror

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